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Lab on a Chip - published by
The Royal Society of Chemistry -
... provides a unique forum for the publication of significant and original work related to miniaturisation (on or off chips) at the micro- and nano-scale across a variety of disciplines including: chemistry, biology, bioengineering, physics, electronics, clinical/medical science, chemical engineering and materials science, which is likely to be of interest to the multidisciplinary community that the journal addresses.
Microfluidics and Nanofluidics - published by
Springer -
... is an international peer-reviewed journal that aims to publish papers in all aspects of microfluidics, nanofluidics and lab-on-a-chip science and technology.
Small - published by
Wiley-Interscience -
Micro and Nano: No Small Matter. Science at the nano- and microscale is currently receiving enormous wordwide interest. Small provides the very best forum for experimental and theoretical studies of fundamental and applied interdisciplinary research at these dimensions. Read an attractive mix of peer-reviewed Communications, Reviews, Concepts, Highlights, Essays, and Full Papers.
Aktuelle wissenschaftliche Fachartikel der
genannten Journale:
Strongly coupled nanocomposites of layered titanate and reduced graphene oxide (RGO) are synthesized by electrostatically derived self-assembly between negatively charged RGO nanosheets and positively charged TiO2 nanosols, which is then followed by a phase transition of the anatase TiO2 component into layered titanate. The resulting nanocomposite consists of thin 2D nanoplates of lepidocrocite-type layered titanate immobilized on the surface of RGO nanosheets. The composite formation with RGO nanosheets is effective not only in promoting the phase transition of anatase TiO2 nanosols, but also in improving the thermal stability of the layered titanate, indicating the role of RGO nanosheets as an agent for directing and stabilizing layered structures. The layered-titanateâRGO nanocomposites exhibit remarkably expanded surface area with the formation of micropores and mesopores. The composite formation with RGO nanosheets gives rise to the disappearance of the reflectance edge of layered titanate in the diffuse reflectance UVâvis spectra, indicating a strong electronic coupling between the RGO and layered titanate. The strong electronic correlation between the two components is further evidenced by the visible-light-induced generation of photocurrents after the hybridization with RGO. The layered-titanateâRGO nanocomposite shows a higher activity for the photodegradation of organic molecules than uncomposited layered titanate, underscoring the usefulness of graphene hybridization in improving the photocatalyst performance of layered titanate. The experimental findings presented here clearly demonstrate that the self-assembly of metal oxide nanoparticles with RGO 2D nanosheets is quite effective not only in synthesizing porous metal-oxideâgraphene nanocomposites with improved photo-induced functionality, but also in achieving strong electronic coupling between RGO and metal oxides.
Strongly coupled nanocomposites of layered titanate and reduced graphene oxide (RGO) are synthesized by self-assembly involving RGO nanosheets and TiO2 nanosols and the following phase transformation of titania. A strong electronic coupling between the two nanospecies remarkably enhances visible light absorption. The hybridization with RGO improves the photocatalytic activity of the layered titanate for the visible-induced generation of photocurrent and the photodegradation of organic molecules.
Fluorescence energy transfer to graphene oxide is studied using covalently linked DNA probes ranging from 4 to 70 base pairs. The characteristic distance and mechanism of energy transfer are reported.
Self-assembly and function of biologically modified metal nanostructures depend on surface-selective adsorption; however, the influence of the shape of metal surfaces on peptide adsorption mechanisms has been poorly understood. The adsorption of single peptide molecules in aqueous solution (Tyr12, Ser12, A3, Flg-Na3) is investigated on even {111} surfaces, stepped surfaces, and a 2 nm cuboctahedral nanoparticle of gold using molecular dynamics simulation with the CHARMM-METAL force field. Strong and selective adsorption is found on even surfaces and the inner edges of stepped surfaces (â20 to â60 kcal/mol peptide) in contrast to weaker and less selective adsorption on small nanoparticles (â15 to â25 kcal/mol peptide). Binding and selectivity appear to be controlled by the size of surface features and the extent of co-ordination of epitaxial sites by polarizable atoms (N, O, C) along the peptide chain. The adsorption energy of a single peptide equals a fraction of the sum of the adsorption energies of individual amino acids that is characteristic of surface shape, epitaxial pattern, and conformation constraints (often β-strand and random coil). The proposed adsorption mechanism is supported and critically evaluated by earlier sequence data from phage display, dissociation constants of small proteins as a function of nanoparticle size, and observed shapes of peptide-stabilized nanoparticles. Understanding the interaction of single peptides with shaped metal surfaces is a key step towards control over self-organization of multiple peptides on shaped metal surfaces and the assembly of superstructures from nanostructures.
Peptide selectionby shaped metal surfaces is shown to be controlled by the size of surface features and the pattern of epitaxial sites. This relationship is described by the surface potential and facilitates the design of attractive peptide sequences for a given surface topography using computational approaches.
An opioid (leucine-enkephalin) conformational analogue forms diverse nanostructures such as vesicles, tubes, and organogels through self-assembly. The nanovesicles encapsulate the natural hydrophobic drug curcumin and allow the controlled release through cation-generated porogens in membrane mimetic solvent.
Lab Chip, 2012, Advance Article DOI: 10.1039/C2LC21225K, Communication
Sungyoung Choi, Jeffrey M. Karp, Rohit Karnik This paper presents the concept of "deterministic cell rolling", a new label-free, single-step, bioaffinity-based separation that combines transient cell-surface molecular interactions with passive hydrodynamic control to separate cells in a continuous process without requiring separate capture and elution steps. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
Mira T. Guo, Assaf Rotem, John A. Heyman, David A. Weitz Droplet microfluidics enables new high-throughput screening applications by using picolitre volumes, kilohertz manipulation and measurement speeds, and high effective concentrations. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Advance Article DOI: 10.1039/C2LC20857A, Paper
Quan Guo, Sarah J. Reiling, Petra Rohrbach, Hongshen Ma We present a microfluidic device for measuring the deformability of red blood cells parasitized by Plasmodium falciparum, the most prevalent species of parasites that cause malaria. Parasitized cells from ring to schizont stages were shown to be 1.5 to 200 times stiffer than uninfected cells, with clearly distinguishable deformability distributions over their respective populations. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Advance Article DOI: 10.1039/C2LC20800H, Paper
Jeongyun Kim, Manjunath Hegde, Sun Ho Kim, Thomas K. Wood, Arul Jayaraman We describe the development of a microfluidic flow cell ([small mu ]FC) device for investigating bacterial biofilm formation in response to different concentrations of soluble signals, either individually or in combination. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
A highly ordered and hierarchicalstructural nanopore array is fabricated via anodizing a pre-patterned aluminum foil under an optimized voltage. A pre-patterned hexagonal nanoindentation array on an aluminum substrate is prepared via the nanosphere lithography method. This pattern leads to an elaborate nanochannel structure with seven nanopores in each nanoindentation after anodization treatment. The structure achieved in our study is new, interesting, and likely to be applied in photonic devices.
An exfoliationâreassemblyâactivation (ERA) approach to lithium-ion battery cathode fabrication is introduced, demonstrating that inactive HCoO2 powder can be converted into a reversible Li1-xHxCoO2 thin-film cathode. This strategy circumvents the inherent difficulties often associated with the powder processing of the layered solids typically employed as cathode materials. The delamination of HCoO2 via a combination of chemical and mechanical exfoliation generates a highly processable aqueous dispersion of [CoO2]â nanosheets that is critical to the ERA approach. Following vacuum-assisted self-assembly to yield a thin-film cathode and ion exchange to activate this material, the generated cathodes exhibit excellent cyclability and discharge capacities approaching that of low-temperature-prepared LiCoO2 (~83 mAh gâ1), with this good electrochemical performance attributable to the high degree of order in the reassembled cathode.
HCoO2 powder is successfully exfoliated in water to yield solution-processable aqueous dispersions of [CoO2]â nanosheets, which are reassembled into self-supporting thin films. Ion exchange with lithium generates Li1-x Hx CoO2 thin films that can be used as reversible cathodes with excellent cyclability and discharge capacities approaching that of low-temperature-prepared LiCoO2.
The concept of a long-term sensor for ion changes in the lysosome is presented. The sensor is made by layer-by-layer assembly of oppositely charged polyelectrolytes around ion-sensitive fluorophores, in this case for protons. The sensor is spontaneously incorporated by cells and resides over days in the lysosome. Intracellular changes of the concentration of protons upon cellular stimulation with pH-active agents are monitored by read-out of the sensor fluorescence at real time. With help of this sensor concept it is demonstrated that the different agents used (Monensin, Chloroquine, Bafilomycin A1, Amiloride) possessed different kinetics and mechanisms of action in affecting the intracellular pH values.
The concept of a long-term sensor for ion changes in the lysosome is presented. The sensor is made by layer-by-layer assembly of oppositely charged polyelectrolytes around ion-sensitive fluorophores, in this case for protons. The sensor is spontaneously incorporated by cells and resides over days in the lysosome. Intracellular changes of the concentration of protons upon cellular stimulation with pH-active agents are monitored by read-out of the sensor fluorescence at real time. With help of this sensor concept it is demonstrated that the different agents used possess different kinetics and mechanisms of action in affecting the intracellular pH values.
Lab Chip, 2012, Accepted Manuscript DOI: 10.1039/C2LC21145A, Paper
Melissa Li Thrombosis is the pathological formation of platelet aggregates which occlude blood flow causing stroke and heart attack-the leading causes of death in developed nations. Instrumentation for diagnosing and exploring treatments... The content of this RSS Feed (c) The Royal Society of Chemistry
Erwin Berthier, Edmond W. K. Young, David Beebe We review the use of PDMS and polystyrene in cell-based microfluidics to provide insight into the central issue of material selection in the emerging interdisciplinary field of bio-microfluidics. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
Loes Segerink In this paper we describe a compact fluorescence detection system for on-chip analysis of beads, comprising a low-cost optical HD-DVD pickup. The complete system consists of a fluorescence detection unit,... The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Accepted Manuscript DOI: 10.1039/C2LC21226A, Paper
Robert Donald Stedtfeld, Dieter Tourlousse, Gregoire Seyrig, Tiffany Stedtfeld, Maggie Kronlein, Scott Price, Farhan Ahmad, Gulari Erdogan, James Tiedje, Syed Hashsham By 2012, point of care (POC) testing will constitute roughly one third of the $59 billion in vitro diagnostics market. The ability to carry out multiplexed genetic testing and wireless... The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Accepted Manuscript DOI: 10.1039/C2LC21284F, Paper
Krzysztof Churski, Tomasz S Kaminski, Slawomir Jakiela, Wojciech Kamysz, Wioletta Baranska-Rybak, Douglas Weibel, Piotr Garstecki We report an automated microfluidic platform for 'digitally' screening the composition space of droplets containing cocktails of small molecules and demonstrate the features of this system by studying epistatic interactions... The content of this RSS Feed (c) The Royal Society of Chemistry
Warren Christopher Ruder, Erica D Pratt, Sasha Bakhru, Metin Sitti, Stefan Zappe, James Antaki , Philip R LeDuc Many physiological systems are regulated by cells that alter their behavior in response to changes in their biochemical and mechanical environment. These cells experience this dynamic environment through an endogenous... The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Accepted Manuscript DOI: 10.1039/C2LC21247A, Paper
Alexander Gansen, Alison Herrick, Ivan Krastev Dimov, Luke Lee, Daniel T Chiu This paper describes the realization of digital loop-mediated DNA amplification (dLAMP) in a sample self-digitization (SD) chip. Digital DNA amplification has become an attractive technique to quantify absolute concentrations of... The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Advance Article DOI: 10.1039/C2LC21017G, Paper
Qin Lu, Alex Terray, Greg E. Collins, Sean J. Hart A unique microfluidic system is developed which enables the interrogation of a single particle by using multiple force balances from a combination of optical force, hydrodynamic drag force, and electrophoretic force. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
The nanochannel (in a porous layer) andion-channel (in a barrier layer) hybrid structure of anodic alumina is used as a protein-trapping device. The transmembrane potential drives the electromigration of the charged proteins (FITC-labeled) into the nanochannels, but electromigration across the barrier layer is impossible due to the size-exclusion effect. As a result, the proteins can be continuously trapped in the nanochannels.
We use molecular dynamics simulations in order to investigate the time evolution of the effect of adsorbed polymer coatings
on the electro-osmotic flow (EOF) in a capillary. Weakly adsorbed coatings show no time-dependent performance, but they do
not strongly reduce the EOF. On the other hand, strongly adsorbed coatings made of longer polymer chains are often quenched
in non-equilibrium conformations that can strongly reduce the EOF over extremely long periods of time. For intermediate adsorption
strengths, we observe that the EOF increases as a function of time due to the relaxation of the coating layer. The concentration
of polymers in solution and the length of the polymer chains also affect the time-dependence of the EOF. These results show
that the quality of electrophoretic separations can depend on the waiting time between the formation of the coating and the
beginning of the separation. We conclude by suggesting experimental tests of our predictions.
Content Type Journal Article
Category Research Paper
Pages 1-7
DOI 10.1007/s10404-012-0944-4
Authors
Owen A. Hickey, Department of Physics, University of Ottawa, 150 Louis-Pasteur, Ottawa, ON K1N 6N5, Canada
James L. Harden, Department of Physics, University of Ottawa, 150 Louis-Pasteur, Ottawa, ON K1N 6N5, Canada
Gary W. Slater, Department of Physics, University of Ottawa, 150 Louis-Pasteur, Ottawa, ON K1N 6N5, Canada
Lab Chip, 2012, Advance Article DOI: 10.1039/C2LC20751F, Paper
Lisa Lafleur, Dean Stevens, Katherine McKenzie, Sujatha Ramachandran, Paolo Spicar-Mihalic, Mitra Singhal, Amit Arjyal, Jennifer Osborn, Peter Kauffman, Paul Yager, Barry Lutz We describe a platform that detects disease-specific antigens and IgM antibodies. The disposable microfluidic cards are based on a flow-through membrane immunoassay carried out on porous nitrocellulose. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Advance Article DOI: 10.1039/C2LC21212A, Paper
William A. Braff, Alexandre Pignier, Cullen R. Buie A novel device utilizing three dimensional insulator based dielectrophoresis promotes low voltage particle and cell trapping with minimal Joule heating. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
Colloidal synthetic approaches to discrete, soluble plasmonic architectures, such as nanorod pairs, offer numerous advantages relative to lithographic techniques, including compositionally asymmetric structures, atomically smooth surfaces, and continuous fabrication. Density-driven colloidal assembly, such as by solvent evaporation, produces some intriguing structures, e.g., particle chains; however, controllability and post-processibility of the final architecture is inadequate. Also the limited quantity of product nominally comprises a broad distribution of assembly size and type. Herein, the high-yield formation of soluble, stable, and compositionally discrete gold nanorod (Au NR) architectures by inducingâthen arrestingâflocculation is demonstrated using bifunctional nanorods and reversible modulation of solvent quality to deplete and reassemble an electrostatic stabilization layer, thereby eliminating the need for an additional encapsulant. Analogous to dimer formation during step-growth polymerization, the initial yield of Au nanorod side-by-side pairs can be greater than 50%. The high solubility and stability of the assembly enable purification, scale-up of nanomolarity solutions, and subsequent chemical modification of the assembled product. As an example, in situ silica deposition via StĂśber synthesis onto the assembled pair produces highly processable nanostructures with a single pair of embedded Au NRs at their center, which exhibit thermal stability at temperatures in excess of 700 °C.
Soluble, stable, and compositionally discrete gold nanorod dimers are synthesized in high-yield by inducingâthen arrestingâflocculation, using bifunctional NRs and reversible modulation of solvent quality to deplete and reassemble an electrostatic stabilization layer. The high solubility and stability of the assembly enable subsequent purification, chemical modification, and thermal stability of the plasmonic properties at temperatures in excess of 700 °C.
Nanostructured lipid multilayers on surfaces are a promising biofunctional nanomaterial. For example, surface-supported lipid multilayer diffraction gratings with optical properties that depend on the microscale spacing of the grating lines and the nanometer thickness of the lipid multilayers have been fabricated previously by dip-pen nanolithography (DPN), with immediate applications as label-free biosensors. The innate biocompatibility of such gratings makes them promising as biological sensor elements, model cellular systems, and construction materials for nanotechnology. Here a method is described that combines the lateral patterning capabilities and scalability of microcontact printing with the topographical control of nanoimprint lithography and the multimaterial integration aspects of dip-pen nanolithography in order to create nanostructured lipid multilayer arrays. This approach is denoted multilayer stamping. The distinguishing characteristic of this method is that it allows control of the lipid multilayer thickness, which is a crucial nanoscale dimension that determines the optical properties of lipid multilayer nanostructures. The ability to integrate multiple lipid materials on the same surface is also demonstrated by multi-ink spotting onto a polydimethoxysilane stamp, as well as higher-throughput patterning (on the order of 2 cm2 sâ1 for grating fabrication) and the ability to pattern lipid materials that could not previously be patterned with high resolution by lipid DPN, for example, the gel-phase phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or the steroid cholesterol.
Nanostructured lipid multilayers are formed by a process that combines the lateral patterning capabilities and scalability of microcontact printing with the topographical control of nanoimprint lithography, and the multimaterial integration aspects of dip-pen nanolithography. This method is scalable and able to make functional optical nanostructures out of lipids that cannot currently be made by other methods.
Flexible graphene paper (GP) pillared by carbon black (CB) nanoparticles using a simple vacuum filtration method is developed as a high-performance electrode material for supercapacitors. Through the introduction of CB nanoparticles as spacers, the self-restacking of graphene sheets during the filtration process is mitigated to a great extent. The pillared GP-based supercapacitors exhibit excellent electrochemical performances and cyclic stabilities compared with GP without the addition of CB nanoparticles. At a scan rate of 10 mV sâ1, the specific capacitance of the pillared GP is 138 F gâ1 and 83.2 F gâ1 with negligible 3.85% and 4.35% capacitance degradation after 2000 cycles in aqueous and organic electrolytes, respectively. At an extremely fast scan rate of 500 mV s â1, the specific capacitance can reach 80 F gâ1 in aqueous electrolyte. No binder is needed for assembling the supercapacitor cells and the pillared GP itself may serve as a current collector due to its intrinsic high electrical conductivity. The pillared GP has great potential in the development of promising flexible and ultralight-weight supercapacitors for electrochemical energy storage.
Flexible graphene paper infiltrated by carbon black (CB) nanoparticles using a vacuum filtration method is developed as a high-performance electrode material for supercapacitors. The self-restacking of graphene sheets is mitigated by the introduction of carbon black as a spacer. The pillared graphene paper-based supercapacitors exhibit excellent electrochemical performance and cyclic stability compared with undoped graphene paper.
The image shows an integrated graphene voltage amplifier, which paves the way for all-graphene analogue electronics. Signal amplification is obtained by fabricating graphene transistors in which the top gate overlaps with the source and drain contacts. This results in full-channel gating and therefore high transconductance at room temperature. The fabricated complementary amplifier has a voltage gain of 3.7 (11.4 dB) at 10 kHz, a total harmonic distortion in the audio frequency range of <1%, a unity-gain frequency of 360 kHz, and a â3 dB bandwidth of 70 kHz. The obtained values demonstrate that, among other applications, the present graphene amplifier is suitable for high-fidelity amplification of audio signals.
Linear alkane polymerization is achieved on the Au(110) surface with 1D constrained nanochannels, which play a key role in the selective CâH activation and CâC bond coupling.
The cover illustrates how the âTrojan Horsesâ known as exosomes are the conveyors in the signaling transduction of nanoparticle-induced systemic immune activation. With the accelerating development and use of nanomaterials in industry and commercial products, the potential risks of manufactured nanoparticles to human health has become concerning. Here, respiratory exposure to manufactured magnetic iron oxide nanoparticles is shown to generate a significant number of exosomes in the lungs of mice. Exosomes are extracellularly secreted membrane vesicles for materials transportation and intercellular communication. In this case, these nanoparticle-induced exosomes are quickly eliminated from the alveolar region, transferring immune activation signals to the immune system. In those individuals who already have pre-existing allergic conditions (known as sensitized individuals), the exosomes can result in a delayed type of hypersensitivity reaction and promote severe allergic responses, whereas in unsensitized individuals, the resulting immune activation response is much lower. For more information, please read the Full Paper âExosomes as Extrapulmonary Signaling Conveyors for Nanoparticle-Induced Systemic Immune Activationâ by G. Nie, Y. Zhao, and co-workers, beginning on page 404.
A graphene audio voltage amplifier is fabricated by overlapping the gate with source/drain contacts. The fabricated complementary amplifier has a voltage gain of 3.7 (11.4 dB) at 10 kHz, a total harmonic distortion in the audio frequency range of <1%, a unity-gain frequency of 360 kHz, and a â3 dB bandwidth of 70 kHz.
The cellular environment impacts a myriad of cellular functions by providing signals that can modulate cell phenotype and function. Physical cues such as topography, roughness, gradients, and elasticity are of particular importance. Thus, synthetic substrates can be potentially useful tools for exploring the influence of the aforementioned physical properties on cellular function. Many micro- and nanofabrication processes have been employed to control substrate characteristics in both 2D and 3D environments. This review highlights strategies for modulating the physical properties of surfaces, the influence of these changes on cell responses, and the promise and limitations of these surfaces in in-vitro settings. While both hard and soft materials are discussed, emphasis is placed on soft substrates. Moreover, methods for creating synthetic substrates for cell studies, substrate properties, and impact of substrate properties on cell behavior are the main focus of this review.
The cellular environment plays a significant role in cell phenotype and function. As such, physical properties of cell culture substrates including topography, roughness, and elasticity may be utilized to investigate the influence of these physical cues on the cellular response. In this review, strategies for modulating the physical properties of surfaces, the influence of these changes on cell responses, and the promise and limitations of these surfaces in in-vitro settings are highlighted, with a particular emphasis on elastic substrates.
Cu2+-modified DNA nanostructures are investigated using differently sized DNA rings that are composed of core and extension motifs. Chemical reduction and current measurements are adopted for verifying Cu2+ modification, and the results provide clear evidence for the co-ordination of Cu2+ in DNA structures.
Evaluation of systemic biosafety of nanomaterials urgently demands a comprehensive understanding of the mechanisms of the undesirable interference and systemic signaling that arises between man-made nanomaterials and biological systems. It is shown that exosomes may act as signal conveyors for nanoparticle-induced systemic immune responses. Exosomes are extracellularly secreted membrane vesicles which act as Trojan horses for the dissemination and intercellular communication of natural nanosized particles (like viruses). Upon exposure to magnetic iron oxide nanoparticles (MIONs), it is possible to dose-dependently generate a significant number of exosomes in the alveolar region of BALB/c mice. These exosomes are quickly eliminated from alveoli into systemic circulation and largely transfer their signals to the immune system. Maturation of dendritic cells and activation of splenic T cells are significantly induced by these exosomes. Furthermore, exosome-induced T-cell activation is more efficient toward sensitized T cells and in ovalbumin (OVA)-sensitized mice than in the unsensitized counterparts. Activation of systemic T cells reveals a T helper 1 polarization and aggravated inflammation, which poses potential hazards to the deterioration of allergic diseases in OVA-sensitized mice. The studies suggest that exosomes may act as conveyors for extrapulmonary signal transduction in nanoparticle-induced immune systemic responses, which are the key in vivo processes of manufactured nanoparticles executing either biomedical functions or toxic responses.
Nanoparticle (NP)-induced exosomes are conveyors in the signaling induction of systemic immunostimulation. Respiratory exposure of magnetic iron oxide nanoparticles (MIONs) can induce exosome secretion from antigen-presenting cells (APCs, probably alveolar macrophages) in the alveolar region. These exosomes sequentially fast transfer to an extrapulmonary site, and extrapulmonary-transferred exosomes are capable of remarkable activation of systemic T cells.
Linear, 2-arm branched, and 4-arm starlike peptides are designed and their antimicrobial and hemolytic activities are characterized. Branching molecular designs are demonstrated to enhance antimicrobial activity and reduce undesired hemolysis, leading to better selectivity towards microbes over mammalian cells. This unique strategy can also be applied to optimize the molecular structures of other types of macromolecular antimicrobials such as polymers.
A simple technique is presented for controlling the shapes of micro- and nanodrops by patterning surfaces with special hydrophilic regions surrounded by hydrophobic boundaries. Finite element method simulations link the shape of the hydrophilic regions to that of the droplets. Shaped droplets are used to controllably pattern planar surfaces and microwell arrays with microparticles and cells at the micro- and macroscales. Droplets containing suspended sedimenting particles, initially at uniform concentration, deposit more particles under deeper regions than under shallow regions. The resulting surface concentration is thus proportional to the local fluid depth and agrees well with the measured and simulated droplet profiles. A second application is also highlighted in which shaped droplets of prepolymer solution are crosslinked to synthesize microgels with tailored 3D geometry.
Droplets conform to hydrophilic regions with hydrophobic boundaries at the macroscale and microscale. Shaped droplets of prepolymer solution become shaped microgels once crosslinked. Sedimenting microparticles contained in a microdroplet form a gradient deposition pattern. Finite element simulations provide a computational design platform for shaped droplets and corresponding surface patterning and microgels.
A reversible preconcentration of gold nanoparticles (AuNPs) can be used for chemical analysis based on surface-enhanced Raman scattering in a microfluidic system. AuNPs homogeneously dispersed in solution are locally preconcentrated by charge-selective ion extraction through a pair of negatively charged polyelectrolyte plugs. This phenomenon creates dynamic hot spots among the preconcentrated AuNPs, which can also be redispersed as required.
This study investigates the use of a natural polysaccharide isolated from mulberry leaves as a nonviral gene vector. Ethylenediamine is chemically grafted to the backbone of a polysaccharide from mulberry leaves (MPS) to acquire nucleic acid binding affinity. A particle-size observation indicates that the cationic mulberry leaf polysaccharide (CMPS) can efficiently combine with plasmid transforming growth factor β1 (TGF-β1) to form nanoscaled particles. In addition, the electrophoresis assay indicates a retarded plasmid migration when the CMPS/pTGF-β1 weight ratio is increased to 30:1. The in vitro cell transfection experiment is performed based on bone marrow mesenchymal stem cells (MSCs) derived from rat femurs and tibias, and the findings reveal that the complex with a CMPS/pTGF-β1 weight ratio of 50:1 exhibits the highest cell transfection effect, which is significantly higher than that of branched poly(ethyleneimine) (PEI) (25 kDa; p = 0.001, Student's t-test) and slightly higher than Lipofectamine 2000. Moreover, the cytotoxicity assay also demonstrates that all of these tested complexes and the plasmid TGF-β1 are nontoxic to mesenchymal stem cells (MSCs). The results of the living cell imaging confirm that more of the CMPS/plasmid TGF-β1 nanoparticles can be taken up and at a faster rate by the MSCs than by the positive control Lipofectamine 2000; these data are consistent with the transfection efficiency data. Together, these results suggest that the CMPS/pTGF-β1 nanoparticle can potentially be developed into a promising alternative for the transfer of therapeutic genes into cells.
A polysaccharide of mulberry leaves (MPS) is isolated from mulberry leaves and cationized by grafting ethylenediamine onto the MPS backbone to obtain the cationic polysaccharide of mulberry leaves (CMPS). The plasmid DNA/CMPS nanoparticles are prepared by combining plasmid DNA with CMPS and used to transfect mesenchymal stem cells, which results in significantly higher transfection efficiency than when Lipofectamine 2000 is used.
Polyvinylpyrollidone (PVP)-capped platinum nanoparticles (NPs) are found to change shape from spherical to flat when deposited on mesoporous silica substrates (SBA-15). Transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and extended X-ray absorption fine structure (EXAFS) analyses are used in these studies. The SAXS results indicate that, after deposition, the 2 nm NPs have an average gyration radius 22% larger than in solution, while the EXAFS measurements indicate a decrease in first neighbor co-ordination number from 9.3 to 7.4. The deformation of these small capped NPs is attributed to interactions with the surface of the SBA-15 support, as evidenced by X-ray absorption near-edge structure (XANES).
2 nm Pt nanoparticles (NPs) are impregnated in mesoporous silica substrates (SBA-15). A change in the Fourier transformation indicates the deformation of the Pt NPs in contact with the SBA-15 surface, from spherical to flat morphology.
Polymeric nanoparticles are promising for gene therapy and stem cell reprogramming using nonviral vectors. A novel assay utilizing nanoparticle tracking analysis is developed to easily quantify the number of plasmids within polymeric nanoparticles while in aqueous solution. Particles effective at co-transfecting primary human fibroblasts are approximately 100 nm in diameter and contain around 100 plasmids per particle.
Fuel-free nanomotors are essential for future in-vivo biomedical transport and drug-delivery applications. Herein, the first example of directed delivery of drug-loaded magnetic polymeric particles using magnetically driven flexible nanoswimmers is described. It is demonstrated that flexible magnetic nickelâsilver nanoswimmers (5â6 Îźm in length and 200 nm in diameter) are able to transport micrometer particles at high speeds of more than 10 Îźm sâ1 (more than 0.2 body lengths per revolution in dimensionless speed). The fundamental mechanism of the cargo-towing ability of these magnetic (fuel-free) nanowire motors is modelled, and the hydrodynamic features of these cargo-loaded motors discussed. The effect of the cargo size on swimming performance is evaluated experimentally and compared to a theoretical model, emphasizing the interplay between hydrodynamic drag forces and boundary actuation. The latter leads to an unusual increase of the propulsion speed at an intermediate particle size. Potential applications of these cargo-towing nanoswimmers are demonstrated by using the directed delivery of drug-loaded microparticles to HeLa cancer cells in biological media. Transport of the drug carriers through a microchannel from the pick-up zone to the release microwell is further illustrated. It is expected that magnetically driven nanoswimmers will provide a new approach for the rapid delivery of target-specific drug carriers to predetermined destinations.
Fuel-free nanomotors are essential for future in-vivo biomedical applications. The first example of towing drug-loaded magnetic polymeric particles using magnetically driven fuel free flexible nanomotors is described. The effect of the cargo size upon the swimming performance is evaluated experimentally and compared to a theoretical model. Potential applications of these cargo-towing motors are demonstrated by using the directed delivery of drug-loaded microparticles to HeLa cancer cells in biological media.
The cover image shows how the shape of micro- and nanodroplets can be controlled by patterning surfaces with special hydrophilic regions surrounded by hydrophobic boundaries. Shaped droplets may be used as a simple tool to controllably pattern planar surfaces with microparticles and cells. Under spiral droplets, a gradient deposition pattern is observed. Shaped droplets of prepolymer solution may also be crosslinked to synthesize microgels with tailored 3D geometry. Finite element simulations provide a design platform by linking the shape of the hydrophilic regions to that of the droplets, microgels, and particle deposition patterns. For more information, please read the Full Paper âDesigner Hydrophilic Regions Regulate Droplet Shape for Controlled Surface Patterning and 3D Microgel Synthesisâ by A. Khademhosseini and co-workers, beginning on page 393.
An apparatus that integrates solid-state nanopore ionic current measurement with a scanning-probe microscope is developed. When a micrometer-scale scanning-probe tip is near a voltage-biased nanometer-scale pore (10â100 nm), the tip partially blocks the flow of ions to the pore and increases the pore access resistance. The apparatus records the current blockage caused by the probe tip and the location of the tip simultaneously. By measuring the current blockage map near a nanopore as a function of the tip position in 3D space in salt solution, the relative pore resistance increases due to the tip and ÎR/R0 is estimated as a function of the tip location, nanopore geometry, and salt concentration. The amplitude of ÎR/R0 also depends on the ratio of the pore length to its radius as Ohm's law predicts. When the tip is very close to the pore surface, â10 nm, experiments show that ÎR/R0 depends on salt concentration as predicted by the Poisson and NernstâPlanck equations. Furthermore, the measurements show that ÎR/R0 goes to zero when the tip is about five times the pore diameter away from the center of the pore entrance. The results in this work not only demonstrate a way to probe the access resistance of nanopores experimentally; they also provide a way to locate the nanopore in salt solution, and open the door to future nanopore experiments for detecting single biomolecules attached to a probe tip.
A novel apparatus that integrates solid-state nanopore ionic current measurement with a scanning probe microscope is constructed and used to characterize the access resistance of solid-state nanopores. The apparatus is capable of recording the current blockage 3D map caused by the probe tip Is(x,y,z) in salt solution. Access resistance is an important parameter for understanding the nanopore translocation process of single DNA and protein molecules.<?br?>
Inspired by the amphiphilicity of graphene oxide (GO), the surface of water is used as a template for the assembly of a GO film. Methacrylate-functionalized GO sheets can be cross-linked instantaneously at the waterâair interface to form a highly wrinkled membrane spreading over an extended area. The multiple covalent linkages amongst the GO sheets enhances the in-plane stiffness of the film compared to noncovalently bonded GO films. The highly convoluted GO membrane can be used in two applications: the promoting of spontaneous stem-cell differentiation towards bone cell lineage without any chemical inducers, and for supercapacitor electrodes. Due to reduced van der Waals restacking, capacitance values up to 211 F gâ1 can be obtained. The scalable and inexpensive nature of this assembly route enables the engineering of membranes for applications in regenerative medicine and energy-storage devices where secondary structures like nanotopography and porosity are important performance enhancers.
Highly wrinkled graphene oxide membranes are formed at the waterâair interface by a cross-linking reaction. The corrugation of the membrane can be controlled by the temperature and concentration of the cross-linking species. The corrugated graphene oxide membrane is a good scaffold for the growth of human mesenchymal stem cells and promotes spontaneous stem-cell differentiation into oesteoblast lineage. The corrugated film structure reduces face-to-face stacking of the graphene and good capacitance values (211 F gâ1) can be obtained when the film is used in supercapacitors.
Morphology control on the 10 nm length scale in mesoporous TiO2 films is crucial for the manufacture of high-performance dye-sensitized solar cells. While the combination of block-copolymer self-assembly with solâgel chemistry yields good results for very thin films, the shrinkage during the film manufacture typically prevents the build-up of sufficiently thick layers to enable optimum solar cell operation. Here, a study on the temporal evolution of block-copolymer-directed mesoporous TiO2 films during annealing and calcination is presented. The in-situ investigation of the shrinkage process enables the establishment of a simple and fast protocol for the fabrication of thicker films. When used as photoanodes in solid-state dye-sensitized solar cells, the mesoporous networks exhibit significantly enhanced transport and collection rates compared to the state-of-the-art nanoparticle-based devices. As a consequence of the increased film thickness, power conversion efficiencies above 4% are reached.
Fabrication of sufficiently thick mesoporous TiO2 photoelectrodes with morphology control on the 10 nm length scale is essential for solid-state dye-sensitized solar cells (ss-DSC). This study of the temporal evolution of block-copolymer-directed mesoporous TiO2 films during annealing and calcination enables the build-up of sufficiently thick films for high-performance ssDSC devices.
The image features a new apparatus that combines a scanning-probe microscope and a solid-state nanopore device. The pore and probe are immersed in an ionic solution where an applied bias voltage creates a current through the pore. The pore is occluded as the probe approaches it, allowing the determination of the 3D access resistance change map outside the nanopore. The device was developed for application in nanopore-based single-molecule DNA sequencing.
Applying nanotechnology to plant science requires efficient systems for the delivery of nanoparticles (NPs) to plant cells and tissues. The presence of a cell wall in plant cells makes it challenging to extend the NP delivery methods available for animal research. In this work, research is presented which establishes an efficient NP delivery system for plant tissues using the biolistic method. It is shown that the biolistic delivery of mesoporous silica nanoparticle (MSN) materials can be improved by increasing the density of MSNs through gold plating. Additionally, a DNA-coating protocol is used based on calcium chloride and spermidine for MSN and gold nanorods to enhance the NP-mediated DNA delivery. Furthermore, the drastic improvement of NP delivery is demonstrated when the particles are combined with 0.6 Îźm gold particles during bombardment. The methodology described provides a system for the efficient delivery of NPs into plant cells using the biolistic method.
Biolistic-mediated delivery of mesoporous silica nanoparticles (MSNs) and DNA to plant cells is performed via two strategies: gold plating the surfaces of MSNs to increase momentum during bombardment, and co-bombardment of the MSNs with 0.6 Îźm gold particles. In both cases, a CaCl2/spermidine-based protocol is used to coat DNA onto the particles.
Lab Chip, 2012, Advance Article DOI: 10.1039/C2LC20918G, Paper
Matthias Wurm, An-Ping Zeng We devised a mechanical approach to obtain a quick and reagentless disruption of mammalian cells and developed a mathematical model to predict cell disruption in microfluidic systems based on CFD-analysis. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Accepted Manuscript DOI: 10.1039/C2LC21189K, Paper
Jasenka M. Verbarg, Kian Kamgar-Parsi, Adam R. Shields, Peter Howell, Frances Ligler While sophisticated assays have been developed and analyzed using lab-on-chip devices, in most cases the sample preparation is still performed off chip. The global need for easy-to-use, disposable testing devices... The content of this RSS Feed (c) The Royal Society of Chemistry
Michele Zagnoni The development of artificial cell membrane microsystems is reviewed, discussing advantages and limitations of classic and unconventional approaches. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
Du Thai Nguyen, Y T. Leho, Aaron Palmer Esser-Kahn For the capture of CO2 from mixed gas streams, materials for increased gas exchange are necessary. Efficient gas exchange systems already exist in the form of vascularized lung-tissue. Herein we... The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Accepted Manuscript DOI: 10.1039/C2LC21203J, Paper
Kyungyong Choi, Jee-Yeon Kim, Jae-Hyuk Ahn, Ji-Min Choi, Maesoon Im, Yang-Kyu Choi A new platform for lab-on-a-chip system is suggested that utilizes a biosensor array embedded in a digital microfluidic device. With field-effect transistor (FET)-based biosensors embedded in the middle of droplet-driving... The content of this RSS Feed (c) The Royal Society of Chemistry
Nanoparticles containing stable holmium (165Ho) are prepared by nanotemplate engineering and subsequently irradiated in a neutron flux to yield 166Ho, a beta-emitting radiotherapeutic isotope. After intraperitoneal injection to mice bearing SKOV-3 ovarian tumors, significant tumor accumulation of the 166Ho-nanoparticles is observed by SPECT imaging indicating the potential of these neutron activatable nanoparticles for internal radiation therapy of ovarian cancer metastases.
The future of lab-on-a-chip devices for the synthesis of nanomaterials hinges on the successful development of high-throughput methods with better control over their size. While significant effort in this direction mainly focuses on developing âdifficult to fabricateâ complex microfluidic reactors, scant attention has been paid to the âeasy to fabricateâ and simple millifluidic systems that could provide the required control as well as high throughput. By utilizing numerical simulation of fluids within the millifluidic space at different flow rates, the results presented here show velocity profiles and residence time distributions similar to the case of microfluidics. By significantly reducing the residence time and residence time distribution, a continuous flow synthesis of ultrasmall copper nanoclusters (UCNCs) with exceptional colloidal stability is achieved. In-situ synchrotron-radiation-based X-ray absorption spectroscopy (XAS) reveal that the as-prepared clusters are about 1 nm, which is further supported by transmission electron microscopy and UVâvis spectroscopy studies. The clusters reported here are the smallest ever produced using a lab-on-a-chip platform. When supported on silica, they are found to efficiently catalyze CâH oxidation reactions, hitherto unknown to be catalyzed by Cu. This work suggests that a millifluidic platform can be an inexpensive, versatile, easy-to-use, and powerful tool for nanoparticle synthesis in general, and more specifically for ultrasmall nanoclusters (UNCs).
The concept of a millifluidic platform as a promising tool for future lab-on-a-chip devices for a controlled and high-throughput synthesis of ultrasmall nanoclusters (UNCs) is presented, both generally and using copper catalysts as a model. The millifluidic platform is versatile, easy to implement, and low cost; and lithography is not required for its fabrication. It is also a potential tool for carrying out time-resolved in situ analysis as larger dimensions for probing will provide a better signal-to-noise ratio.
Seila Selimovic, Ali Khademhosseini Self-similar topographies on shrink-film for cell culture - Optically adjustable, dynamic microfluidic chips - Protein profiling with microgels The content of this RSS Feed (c) The Royal Society of Chemistry
Jurg Dual, Philipp Hahn, Ivo Leibacher, Dirk Moller, Thomas Schwarz This acoustofluidics tutorial describes different measurement techniques used for the experimental characterization of ultrasonic particle manipulation devices. The content of this RSS Feed (c) The Royal Society of Chemistry
Henne van Heeren There is much diversity in microfluidics, but serious work on development of standards is being done by several groups, and the first results become visible. This will undoubtedly have a large impact on all working in this field. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Advance Article DOI: 10.1039/C2LC20771K, Paper
Yi-Heng Sen, Tarun Jain, Carlos A. Aguilar, Rohit Karnik Multiple measurements on the same DNA molecule translocating through a nanochannel enable enhanced discrimination between molecules of different lengths. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
Hollow microstructures serve many useful applications in the fields of microsystems, chemistry, photonics, biology and others.
Current fabrication methods of artificial hollow microstructures require multiple fabrication steps and expensive manufacturing
tools. The paper reports a unique one-step fabrication process for the growth of hollow polymeric microstructures based on
electric field-assisted capillary action. This method demonstrates the manufacturing of self-encapsulated microstructures
such as hollow microchannels and microcapsules of around 100-Îźm height from an initial polymer thickness of 22 Îźm. Microstructure
caps of several microns thickness have been shown to keep their shape under bending or delamination from the substrate. The
inner surface of hollow microstructures is shown to be smooth, which is difficult to achieve with current methods. More complicated
structures, such as a microcapsule array connected with hollow microchannels, have also been manufactured with this method.
Numerical simulation of the resist growth process using COMSOL Multiphysics finite element analysis software has resulted
in good agreement between simulated and experimental results on the overall shape of the resulting structures. These results
are very positive and demonstrate the speed, versatility and cost-effectiveness of the method.
Content Type Journal Article
Category Research Paper
Pages 1-8
DOI 10.1007/s10404-012-0942-6
Authors
H. Chen, State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 3888 Dongnanhu Road, Changchun, Jilin, Peopleâs Republic of China
W. Yu, State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 3888 Dongnanhu Road, Changchun, Jilin, Peopleâs Republic of China
S. Cargill, Microsystems Engineering Center (MISEC), School of Engineering and Physical Sciences, Heriot-Watt University, Earl Mountbatten Building, Edinburgh, EH14 4AS UK
M. K. Patel, School of Computing and Mathematical Sciences, University of Greenwich, Old Royal Naval College, Park Row, London, SE10 9LS UK
C. Bailey, School of Computing and Mathematical Sciences, University of Greenwich, Old Royal Naval College, Park Row, London, SE10 9LS UK
C. Tonry, School of Computing and Mathematical Sciences, University of Greenwich, Old Royal Naval College, Park Row, London, SE10 9LS UK
M. P. Y. Desmulliez, Microsystems Engineering Center (MISEC), School of Engineering and Physical Sciences, Heriot-Watt University, Earl Mountbatten Building, Edinburgh, EH14 4AS UK
The electrohydrodynamic (EHD) vortices produced by an electric current in freely suspended liquid crystal (LC) films of N-(4-methoxybenzylidene)-4-butylaniline (MBBA), convert to a pure rotation in the presence of external electric field (
Eext
) perpendicular to the current direction. Here, the direction and strength of the rotation are precisely under control by
our self-made device called âliquid-film motorâ. In this paper, we present experimental observations of the EHD fluid flow
when external electric field varies from zero to a value in which pure rotation on the liquid crystal (LC) film is observed.
We also show experimentally that the presence of external electric field causes a great decrease in the current produced by
the voltage VJ required for observing EHD vortices in freely suspended films of MBBA. The LC films begin to rotate when EextVJ reaches a threshold value. This threshold is investigated experimentally as a function of voltage VJ and the external electrical field
Eext
.
Content Type Journal Article
Category Research Paper
Pages 1-7
DOI 10.1007/s10404-012-0943-5
Authors
R. Shirsavar, Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran, Iran
A. Amjadi, Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran, Iran
M. R. Ejtehadi, Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran, Iran
M. R. Mozaffari, Department of Physics, Qom University, P.O. Box 3716146611, Qom, Iran
M. S. Feiz, Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran, Iran
A new microfluidic chip integrated with 120 parallelmicrobial suspension culture units is demonstrated. Various bacterial strains and even yeast can be cultivated on the chip. With a high degree of integration and simple fabrication process, this chip could be a central component for future high-throughput microbial screening and selection systems.
A light-controlled, smart-gating nanochannel has been realized by photo-induced pH change in the environmental solution, which can drive the conformation response of motor-DNA molecules on the inner surfaces of the nanochannel. Such ion-gating might find applications in areas such as the control of mass-delivery, sensing, catalysis, or related fields.
Lab Chip, 2012, Advance Article DOI: 10.1039/C2LC20588B, Paper
Phuoc Long Truong, Byung Woo Kim, Sang Jun Sim By experimentally determining the optimal sensitivity of Au nanorods for an individual optical nanosensor and optimizing the accessibility between the carboxyl groups of the self-assembled monolayer on the gold nanorod surface and the PSA mAb, the individual Au nanorod sensor was effectively exploited for the detection of a PSA biomarker with 1 aM sensitivity ([similar]6 [times] 105 molecules). To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
A single microfluidic chip consisting of six microfluidic flow-focusing devices operating in parallel was developed to investigate
the feasibility of scaling microfluidic droplet generation up to production rates of hundreds of milliliters per hour. The
design utilizes a single inlet channel for both the dispersed aqueous phase and the continuous oil phase from which the fluids
were distributed to all six flow-focusing devices. The exit tubing for each of the six flow-focusing devices is separate and
individually plumbed to each device. Within each flow-focusing device, the droplet size was monodisperse, but some droplet
size variations were observed across devices. We show that by modifying the flow resistance in the outlet channel of an individual
flow-focusing device it is possible to control both the droplet size and frequency of droplet production. This can be achieved
through the use of valves or, as is done in this study, by changing the length of the exit tubing plumbed to the outlet of
the each device. Longer exit tubing and larger flow resistance is found to lead to larger droplets and higher production frequencies.
The devices can thus be individually tuned to create a monodisperse emulsion or an emulsion with a specific drop size distribution.
Content Type Journal Article
Category Research Paper
Pages 1-9
DOI 10.1007/s10404-012-0941-7
Authors
Molly K. Mulligan, Department of Mechanical and Industrial Engineering, University of Massachusetts, 160 Governors Drive, Amherst, MA 01003, USA
Jonathan P. Rothstein, Department of Mechanical and Industrial Engineering, University of Massachusetts, 160 Governors Drive, Amherst, MA 01003, USA
Branched nanostructures are of great interest because of their promising optical and electronic properties. For successful and reliable integration in applications such as photovoltaic devices, the thermal stability of the nanostructures is of major importance. Here the different domains (CdSe cores, CdS pods) of the heterogeneous octapods are shown to have different thermal stabilities, and heating is shown to induce specific shape changes. The octapods are heated from room temperature to 700 °C, and investigated using (analytical and tomographic) transmission electron microscopy (TEM). At low annealing temperatures, pure Cd segregates in droplets at the outside of the octapods, indicating non-stochiometric composition of the octapods. Furthermore, the tips of the pods lose their faceting and become rounded. Further heating to temperatures just below the sublimation temperature induces growth of the zinc blende core at the expense of the wurtzite pods. At higher temperatures, (500â700 °C), sublimation of the octapods is observed in real time in the TEM. Three-dimensional tomographic reconstructions reveal that the four pods pointing into the vacuum have a lower thermal stability than the four pods that are in contact with the support.
Both in situ and ex situ annealing experiments are performed on CdSe/CdS octapods. At high temperatures (500â700 °C), sublimation of the octapods is observed in real time with transition electron microscopy. Three-dimensional tomographic reconstructions of partially sublimated octapods reveal that the pods that are not in contact with the support membrane are the first to sublimate.
Hollow porous LiMn2O4 microcubes are prepared via a facile template route involving annealing MnCO3 microcubes, followed by treatment with diluted acid, chemical lithiation with LiI, and calcination under vacuum at 350 °C. These hollow porous nanomaterials with large void volume and high surface area show improved rate capability and excellent cycle life.
Lab Chip, 2012, Advance Article DOI: 10.1039/C2LC21028B, Paper
Mohammad Abdolahad, Mohammad Taghinejad, Hossein Taghinejad, Mohsen Janmaleki, Shams Mohajerzadeh Great mechanical and electrical interactions between cancer cells and carbon nanotubes were applied for a new cancer cell impedance biosensor. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Accepted Manuscript DOI: 10.1039/C2LC21072J, Communication
Alon Greenbaum, Uzair Sikora, Aydogan Ozcan We report a field-portable lensfree microscope that can image dense and connected specimens with sub-micron resolution over a large field-of-view of ~30 mm2 (i.e., ~6.4 mm x ~4.6 mm) using... The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Accepted Manuscript DOI: 10.1039/C2LC40052A, Paper
Pengyuan Yang, Ji Ji, Liping Guo, Yiqing Zhao, Chang Ji, Baohong Liu A spherical liquid-liquid interface can be obtained by dispersing one liquid phase into the other to form droplets, which will facilitate the two-phase reactions between the immiscible participating fluids. The... The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Accepted Manuscript DOI: 10.1039/C2LC21239K, Paper
Kyung-Ho Lee, Ka-Young Lee, Ju-Young Byun, Byung-Gee Kim, Dong-Myung Kim A system for expression and in situ display of recombinant proteins on microbead surface is described. Biotinylated PCR products were immobilized on microbead surfaces, which were then embedded in a... The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Accepted Manuscript DOI: 10.1039/C2LC21217J, Paper
Giuseppina Simone An in situ method of modifying the chemistry and topology of microfluidic surfaces in order to mimic in vivo cellular mechanisms is described. The binding of functionalised microbeads to microfluidic... The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Accepted Manuscript DOI: 10.1039/C2LC21219F, Paper
Guangwei Si, Wei Yang, Shuangyu Bi, Chunxiong Luo, Qi Ouyang We developed a multiple-channel microfluidic device for bacterial chemotaxis detection. Some characters such as easy operation, parallel sample adding design and fast result readout make this device convenient for most... The content of this RSS Feed (c) The Royal Society of Chemistry
At an acidic pH, cytosine-rich DNA strands can form i-motif tetramers. Pillar-like DNA structures are self-assembled with such i-motifs as the central stems. The central stem has some overhanging structures that can enable hybridization with complementary units by WatsonâCrick pairing and, thus, multiple i-motifs can join to form the pillar.
Controllable synthesis of single-crystalline lamellae of copper tetracyano-p- quinodimethane (CuTCNQ, phase II) is achieved, and mass-produced devices or device arrays based on symmetrical Cr/Au gap electrodes are fabricated in situ. The devices exhibit semiconductor properties important for the understanding of CuTCNQ.
Three-dimensional ordered inverse-opal films bearing a reactive trifluoroacetyl group are successfully constructed. Through the specific reaction between cyanide and trifluoroacetyl, the photonic films can selectively detect sub-micromolar levels of cyanide by distinct structural color change. Labeled molecules are not necessary for the sensing mechanism.
Three-dimensional ordered inverse-opal films bearing a reactive trifluoroacetyl group are successfully constructed. Through the specific reaction between a cyanide ion and trifluoroacetyl group and without the use of labels, these photonic films can selectively detect sub-micromolar levels of cyanide by a distinct structural color change.
This review summarizes the work conducted in the last decade on the fabrication of mesostructured patterns, which have lateral dimensions within the nano- and microscales, over a wafer-scaled size by means of dynamic self-assembly using LangmuirâBlodgett (LB) transfer or dip-coating. First, strategies to form mesostructures from a homogeneous Langmuir monolayer with controlled shape, size, and patterns alignment will be presented, followed by a detailed theoretical explanation of the pattern formation. In addition, the patterning of nanocrystals and other chemicals with LB transfer or other dynamic processes, such as dip-coating, will be summarized.
The recent experimental and theoretical work on the fabrication of well-ordered mesoscopic structural surfaces over large areas is reviewed. Methods such as the LangmuirâBlodgett (LB) technique are described. Furthermore, the patterning of materials with LB transfer or other dynamic processes such as dip-coating is summarized.
Three-dimensional force spectroscopy measurements on 3,4,9,10-perylene-tetra-carboxylic dianhydride adsorbed on Ag(111) are combined with first-principles calculations to characterize the dissipative tipâmolecule interactions with submolecular resolution. The experiments reveal systematic differences between the energy dissipation at the end groups and the center of the molecules that change with the tipâsample distance. Guided by the strength of the experimental conservative forces, an Ag-contaminated Si tip is identified as the likely tip termination in the experiments. Based on this tip configuration, the energy dissipation in the tipâsample contact is determined from the approach and retraction force curves calculated as a function of distance for different molecule sites. These calculations provide an explanation for the experimental trends in terms of the competition between localized dissipation mechanisms involving the quite mobile oxygen atoms on the sides of the molecule, and global molecular deformations involving the more rigid perylene core. The results confirm that the observed dissipation can be explained in terms of adhesion hysteresis and show the power of combined experimentalâtheoretical spectroscopy studies in the characterization of the underlying microscopic mechanisms.
3D force-field spectroscopy investigations of an organic semiconductor adsorbed on the Ag(111) surface reveal systematic differences in the energy dissipation as a function of tipâsample distance for different subareas of the molecules. The underlying atomic-scale processes are identified by first-principles calculations. The observed trends are assigned to competing localized mechanisms based on adhesion hysteresis involving the mobile end groups and the more rigid core of the molecules.
Cucurbit[n]urils (CB[n]) have great potential in material and medical applications due to their advantageous molecular recognition properties. Despite organic microcrystals being highly desirable in materials science and the medical industry, CB[n]-based micro- and nanocrystals have not been reported. A facile and efficient approach for producing CB[8]-based organic crystals with well-defined micro- and nanostructures is described, based on the unique hostâguest chemistry of CB[8] macrocycle with small guest molecules. The described strategy allows fabrication of micro- and nanocrystals with multiple morphologies and compositions by simply adjusting the preparation conditions and the type of guest molecules. The mechanisms for the formation of the micro/nanocrystals are studied, and morphology-dependent optical and thermal properties typical of organic micro/nanocrystals are described. Additionally, attractive potentials of the prepared microcrystals are shown upon storing small molecules, and in optical applications. The molecular recognition abilities of CB[8] are highlighted in both its preparation process and potential application.
Controllable fabrication of cucurbit[8]uril (CB[8])-based organic crystals with tunable morphologies and good uniformity is described. Small molecules such as indole, quinoline, or coumarin are packed in the micro/nanocrystals by location inside the cavity of CB[8]. Morphology-dependent properties of the micro/nanocrystals are observed.
Lab Chip, 2012, Accepted Manuscript DOI: 10.1039/C2LC21083E, Communication
Jason Paul Beech, Stefan H Holm, Karl Adolfsson, Jonas O Tegenfeldt While size has been widely used as a parameter in cellular separations, in this communication we show how shape and deformability, a mainly untapped source of specificity in preparative and... The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Accepted Manuscript DOI: 10.1039/C2LC21242K, Paper
Yuji Fujii, Terence G Henares, Kunio Kawamura, Tatsuro Endo, Hideaki Hisamoto To enhance sensitivity and facilitate easy sample introduction into a combinable poly(dimethylsiloxane) (PDMS) capillary (CPC) sensor array, bulk and surface modifications of PDMS were conducted to prepare "black" PDMS covered... The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Accepted Manuscript DOI: 10.1039/C2LC21110F, Paper
Jochen Rupp We present a disposable microarray hybridization chamber with an integrated micropump to speed up diffusion based reaction kinetics by generating convective flow. The time-to-result for the hybridization reaction was reduced... The content of this RSS Feed (c) The Royal Society of Chemistry
Curtis David Chin, Vincent Linder, Samuel K Sia A large part of the excitement behind microfluidics is in its potential for producing practical devices, but surprisingly few lab-on-a-chip based technologies have been successfully introduced into the market. Here,... The content of this RSS Feed (c) The Royal Society of Chemistry
Jong-Hoon Kim, Woon-Hong Yeo, Zhiquan Shu, Scott D Soelberg, Shinnoske Inoue, Dinesh Kalyanasundaram, John Ludwig, Clement E Furlong, James J Riley, Kris Weigel, Gerard A Cangelosi, Kieseok Oh, Kyong-Hoon Lee, Dayong Gao, Jae-Hyun Chung A long-sought goal for tuberculosis diagnosis is a rapid, accurate tool that is compatible with the needs of tuberculosis-endemic settings. An immunofluorescence microtip sensor is described that detects Mycobacterium tuberculosis... The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Advance Article DOI: 10.1039/C2LC21122J, Communication
Irina V. Nesterova, Mateusz L. Hupert, Malgorzata A. Witek, Steven A. Soper We report a polymer-based microfluidic device that establishes an efficient and inexpensive platform with performance comparable to a commercially available bench-top system. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
The production of reusable stamps for the creation of high-resolution patterns of functional nanoparticles is demonstrated. A patterned stamp is cleaned by removing nanoparticles in the recessed regions of the stamp, using a UV-curable adhesive, before moving on to the next cycle of printing with the stamp. A high-resolution patterning technique using rigid stamps with a low surface energy and the repeated use of the reusable stamps for defining sub-100 nm scale features is demonstrated. Color patterning has also been performed using just one color per stamp, then by the use of one stamp for multiple colors.
Multiple-allergen testing for high throughput and high sensitivity requires the development of miniaturized immunoassays that allow for a large test area and require only a small volume of the test analyte, which is often available only in limited amounts. Developing such miniaturized biochips containing arrays of test allergens needs application of a technique able to deposit molecules at high resolution and speed while preserving its functionality. Lipid dip-pen nanolithography (L-DPN) is an ideal technique to create such biologically active surfaces, and it has already been successfully applied for the direct, nanoscale deposition of functional proteins, as well as for the fabrication of biochemical templates for selective adsorption. The work presented here shows the application of L-DPN for the generation of arrays of the ligand 2,4-dinitrophenyl[1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[6-[(2,4-dinitrophenyl)amino]hexanoyl] (DNP)] onto glass surfaces as a model system for detection of allergen-specific Immunoglobin E (IgE) antibodies and for mast cell activation profiling.
Multiple-allergen testing at high throughput and high sensitivity requires the development of miniaturized immunoassays that would allow for large test areas and require only a small volume of the test analyte. Application of lipid dip-pen nanolithography for the generation of arrays of the ligand 2,4-dinitrophenyl[1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[6-[(2,4-dinitrophenyl)amino]hexanoyl] (DNP)] onto glass surfaces is presented as a model system for the detection of allergen-specific IgE (immunoglobulin E) antibodies and for mast cell activation profiling.
Lab Chip, 2012, 12,882-891 DOI: 10.1039/C2LC21035E, Paper
Ali Fallah-Araghi, Jean-Christophe Baret, Michael Ryckelynck, Andrew D. Griffiths A microfluidic system in which droplets containing in vitro translated enzymes are screened at up to 2000 droplets per second. The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Advance Article DOI: 10.1039/C2LC21152A, Paper
Samuel M. Stavis, Jon Geist, Michael Gaitan, Laurie E. Locascio, Elizabeth A. Strychalski Complex nanofluidic confinement established a free energy landscape that enabled passive control over the transport and concentration of DNA molecules. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, 12,986-993 DOI: 10.1039/C2LC21181E, Paper
Ioana Dumitrescu, David F. Yancey, Richard M. Crooks We describe a dual-electrode microelectrochemical device suitable for characterising electrocatalysts. The content of this RSS Feed (c) The Royal Society of Chemistry
Eric T. Ritschdorff, Rex Nielson, Jason B. Shear Scanning a dynamic mask with multiple laser foci provides parallelism for multiphoton lithography of large-scale microstructures. The content of this RSS Feed (c) The Royal Society of Chemistry
Chaotic micromixers such as the staggered herringbone mixer developed by Stroock et al. allow efficient mixing of fluids even
at low Reynolds number by repeated stretching and folding of the fluid interfaces. The ability of the fluid to mix well depends
on the rate at which âchaotic advectionâ occurs in the mixer. An optimization of mixer geometries is a non-trivial task which
is often performed by time consuming and expensive trial and error experiments. In this paper an algorithm is presented that
applies the concept of finite-time Lyapunov exponents to obtain a quantitative measure of the chaotic advection of the flow
and hence the performance of micromixers. By performing lattice Boltzmann simulations of the flow inside a mixer geometry,
introducing massless and non-interacting tracer particles and following their trajectories the finite time Lyapunov exponents
can be calculated. The applicability of the method is demonstrated by a comparison of the improved geometrical structure of
the staggered herringbone mixer with available literature data.
Content Type Journal Article
Category Research Paper
Pages 1-9
DOI 10.1007/s10404-012-0936-4
Authors
Aniruddha Sarkar, Department of Applied Physics, Eindhoven University of Technology, Den Dolech 2, 5600Â MB Eindhoven, The Netherlands
Ariel NarvĂĄez, Department of Applied Physics, Eindhoven University of Technology, Den Dolech 2, 5600Â MB Eindhoven, The Netherlands
Jens Harting, Department of Applied Physics, Eindhoven University of Technology, Den Dolech 2, 5600Â MB Eindhoven, The Netherlands
In this research, molecular dynamics simulations of water nanojet ejection out of nozzle holes with various sizes under various
pressing forces are performed. The water molecules are ejected out the nozzle by a back plate on which a constant force is
applied. The results of MD simulations of water ejection show that after one ejection, about 1.3â2.5% of total molecules accumulate
on the nozzle plate surface. These molecules affect the ejection of water jet thereafter. The cause of the accumulation of
wetting water is investigated by analyzing the trajectories of these molecules. It is found that in the firing chamber near
the nozzle plate wall, the arrangement of water molecules is aligned by the surface topology of the metal wall. Water molecules
are packed into filamentous structure and these lines stack up at equal distances to each other. Water molecules drift along
these lines, the trajectories of these molecules are sinuous, the velocity directions of them are random; molecules drift
along the parallel lines until they reach a region of low pressure beneath the nozzle opening. These molecules eject out through
the edge of the nozzle, they fall back on to the nozzle surface and eventually deposit on the nozzle surface due to low ejection
velocity.
Content Type Journal Article
Category Research Paper
Pages 1-12
DOI 10.1007/s10404-012-0938-2
Authors
Jau-Wen Lin, Department of Mechanical Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung, 80785 Taiwan, ROC
Lab Chip, 2012, 12,971-976 DOI: 10.1039/C2LC20904G, Paper
Youngsoon Kim, David P. Lyvers, Alexander Wei, Ronald G. Reifenberger, Philip S. Low We present a novel pathogen recognition methodology that involves capture of the desired pathogen by its cognate siderophore onto a chip. The content of this RSS Feed (c) The Royal Society of Chemistry
Joon S. Shim, Chong H. Ahn An integrated microfilter has been simply implemented at the inlet of a microchannel using hetero-packed beads and applied to realize the on-chip stationary blood/plasma separator. The content of this RSS Feed (c) The Royal Society of Chemistry
A unique algorithm named single pixel evaluation (SPE) has been developed to enhance the resolution of micro-PIV to its physical
limit, one pixel. Based on some presumed conditions, an experimentally ultimate in-plane resolution of micro-PIV is estimated.
An extremely high resolution of 64.5 nm can be achieved when a 60-nm particle is resolved. However, there exist discrepancies
between the analytic predictions and the experimental measurements. Therefore, another task of this paper is to characterize
the algorithm and provide practical criteria as applying SPE. Five general parameters were investigated with synthetic particle
images governed by a parabolic flow profile. The parameters include particle image quality, particle image density, search
radius, particle image displacement, and particle image diameter. The results indicate that all parameters have significant
improvements on the random error, yet minor or no effects on the bias error. The tendencies of optimal values subject to different
parameters are discussed in the context. Moreover, SPE was compared with fast Fourier transform-based cross-correlation under
a desired signal-to-noise ratio. To complete the study, measurements in a straight microchannel were implemented to verify
the predictions and the estimated resolution. The measured images following the suggested criteria showed qualitatively good
agreements with the predictions. In practice, a spatial resolution of only 129 nm was achieved since the minimal particle
diameter that can be visualized by our micro-PIV system was around 100 nm.
Content Type Journal Article
Category Research Paper
Pages 1-16
DOI 10.1007/s10404-012-0939-1
Authors
Han-Sheng Chuang, Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
Lichuan Gui, IIHR-Hydroscience and Engineering, The University of Iowa, Iowa City, IA, USA
Steven T. Wereley, School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA
Thermosensitive poly(N-isopropylacrylamide) (PNIPAM)/Au nanoparticle (NP) nanocomposite hydrogels are synthesized by in situ Îł-radiation-assisted polymerization of N-isopropylacrylamide monomer aqueous solution in the presence of HAuCl4¡4H2O. In this reaction, the PNIPAM hydrogels and the Au NPs are formed simultaneously, thus demonstrating an easy and straightforward synthetic strategy for the preparation of a uniform nanocomposite. The results suggest that increasing the monomer content during the preparation of nanocomposite materials can increase the sizes of Au NPs. The effects of irradiation dose and concentration of HAuCl4¡4H2O on the optical and thermal properties of the hydrogel are also investigated. The PNIPAM/Au nanocomposite hydrogels act as an excellent catalyst for the conversion of o-nitroaniline to 1,2-benzenediamine, and the catalytic activity of the composite hydrogel can be tuned by the volume transition of PNIPAM. The in situ polymerization of monomer and reduction of metal ions initiated by a âcleanâ and âgreenâ Îł-radiation technique can be extended to the efficient synthesis of other nanocomposite materials.
A clean and green Îł-radiation technique is employed for the synthesis of thermosensitive poly(N-isopropylacrylamide)/Au nanoparticle (NP) nanocomposite hydrogels by the in situ polymerization of monomer and reduction of gold ions. The hydrogels and uniform Au NPs are formed simultaneously in the absence of any initiator, crosslinking, or reducing agent.
Well-designed nanoparticle-mediated, image-guided cancer therapy has attracted interest for increasing the efficacy of cancer treatment. A new class of smart theragnostic nanoprobes employing cetuximab (CET)-conjugated polyethylene glycol (PEG)ylated gold nanorods (CET-PGNRs) is presented; these nanoprobes target epithelial cancer cells using near-infrared light. The cetyltrimethylammonium bromide bilayer on GNRs is replaced with heterobifunctional PEG (COOH-PEG-SH) to serve as a biocompatible stabilizer and to increase specificity. The carboxylated GNRs are further functionalized with CET using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC-NHS) chemistry. To assess the potential of such GNRs, their optical properties, biocompatibility, colloidal stability, in vitro/in vivo binding affinities for cancer cells, absorption imaging, and photothermal therapy effects are investigated. CET-PGNRs exhibit excellent tumor targeting ability and strong potential for simultaneous absorption imaging and photothermal ablation of epithelial cancer cells.
A theragnostic nanoprobe using near-infrared radiation and polyethylene glycol (PEG)ylated gold nanorods (GNRs) conjugated to cetuximab is presetend. The nanoprobe has excellent tumor targeting ability and strong potential for simultaneous absorption imaging and photothermal ablation of epithelial cancer cells.
A charged microparticle can be trapped in an aqueous environment by forming a narrow virtual poreâa cylindrical space region in which the particle motion in the radial direction is limited by forces emerging from dynamical interactions of the particle charge and dipole moment with an external radiofrequency quadrupole electric field. If the particle satisfies the trap stability criteria, its mean motion is reduced exponentially with time due to the viscosity of the aqueous environment; thereafter the long-time motion of particle is subject only to random, Brownian fluctuations, whose magnitude, influenced by the electrophoretic and dielectrophoretic effects and added to the particle size, determines the radius of the virtual pore, which is demonstrated by comparison of computer simulations and experiment. The measured size of the virtual nanopore could be utilized to estimate the charge of a trapped micro-object.
Charged microparticles in an aqueous environment are trapped in microsized tunable aqueous virtual pores (AVP) formed by quadrupole electric fields of a linear Paul microtrap. The AVP is controlled by the electrophoretic and dielectrophoretic forces, and its main advantage over a physical nanopore is relaxation of critical dimension control, which simplifies device fabrication. The radial dimension of the desired trapping region could be significantly smaller than the actual fabricated dimensions.
The electrical manipulation of a patterned lipid membrane is employed for the highly reliable, straightforward, and sensitive detection of membrane receptorâligand interactions in an array platform. Target-binding modulates lipid fluidity and membrane phase, and the difference in membrane fluidity with different target concentrations is clearly distinguished in an amplifiable manner. This is achieved by locally concentrating charged, fluorescent lipids during electrophoresis.
Mechanically interlocked molecules, such as catenanes and rotaxanes, are at the heart of the development of molecular machines chemistry. They are able to self-organize, self-assemble, and self-control themselves into new materials with potential application as molecular devices. In this review, an overview of some recent progress on molecular machines is given, including new methodologies for their synthesis and self-assembly and their recent applications as dual or multilevel fluorescent molecular switches, as potential sensors, and even as a molecular-level transporter. In one development, a molecular machine containing a charge-transfer chromophore was designed to generate controllable aggregate structures through the reversible movement of a macrocycle over a thread; this was done in order to better understand the application of a molecular shuttle in solid state. Light is shed on how the novel properties and functions of molecular machines are extended, and examples of the ways in which molecular machines have been applied to the design and process of intelligentized systems are provided.
Recent progress in the constructionof functional smart molecular machines based on conjugated organic molecules with photo-electronic activity is summarized. Additionally, light is shed on how the novel functions of molecular machines are extended, and examples of the ways in which conjugated organic molecules have been, or can be, applied to the design and process of intelligentized systems are presented.
Lab Chip, 2012, Accepted Manuscript DOI: 10.1039/C2LC21233A, Paper
Martin Straver, Mathieu Odijk, Wouter Olthuis, Albert van den Berg In this paper an easy to fabricate SU8/glass-based microfluidic sensor is described with two closely spaced parallel electrodes for highly selective measurements using the redox cycling effect. By varying the... The content of this RSS Feed (c) The Royal Society of Chemistry
The successful covalent functionalization of quartz and n-type 6H-SiC with organosilanes and benzo[ghi]perylene-1,2-dicarboxylic dye is demonstrated. In particular, wet-chemically processed self-assembled layers of aminopropyltriethoxysilane (APTES) and benzo[ghi]perylene-1,2-dicarboxylic anhydride are investigated. The structural and chemical properties of these layers are studied by contact angle measurements, attenuated total reflection infrared (ATR-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The optical properties are measured by confocal microscopy. The wetting angles observed for the organic layers are ι = 68° for the APTES-functionalized surface, while angles of ι = 85° and 78° are determined for dye-functionalized quartz and 6H-SiC surfaces, respectively. However, not all amino groups of the APTES-functionalized surfaces react to bind dye molecules. Further dye functionalization is not uniform throughout the surface, showing different island sizes of the dye and including different chemical environments. The quartz surface exhibits a higher packing density of dyes than the 6H-SiC surface. The fluorescence lifetimes of the surface-attached dye show double exponential decays of about 1.4 and 4.2 ns, largely independent of the substrates.
Functionalization of SiC with a fluorescent dye is achieved in two steps. On the hydroxyl-terminated substrate, a silanization reaction first covalenty binds a 3-aminopropyl triethoxysilane (APTES) linker molecule at which the perylene dye is subsequently attached. Spatially resolved fluorescence lifetime measurements indicate that the dye is electronically isolated from the substrate. Furthermore, the formation of HâH complexes is observed.
The self-assembly of a tetrathiafulvalene (TTF)-based molecular gelator with a dendron substituent into a gel is described. Scanning electron microscope and atomic force microscope studies show that the xerogels exhibit rope-like frameworks or interwoven nanofibers, depending on the polarity of solvent from which the gel is formed. Gels containing chloranil can also be successfully prepared. Interestingly, this two-component gel can be easily transformed into solution after the addition of either Sc3+ or Pb2+. Both absorption and electron spin resonance (ESR) spectroscopic investigations reveal that the TTF unit is oxidized into TTF.+ by chloranil in the presence of either Sc3+ or Pb2+. Moreover, the gel phase can be restored by reduction of TTF.+ into the neutral form using magnesium.
Molecular gels of a dendron-attached tetrathiafulvalene (TTF) can be modulated by varying the oxidation state of the tetrathiafulvalene through oxidation with the ensemble of chloranil and Sc3+/Pb2+ and reduction with magnesium. The dendron-substituted TTF 1 can self-assemble in several solvents to form gels which exhibit a rope-like framework or interwoven nanofibers, depending on the polarity of the solvent from which the gel is formed.
Please click here: A facile two-step functionalization strategy for silicon oxide-based substrates generates a stable platform for surface click chemistry via direct writing. The suitability of the obtained substrates is proven by patterning with two different direct-writing techniques and three different molecules.
A novel dipolar-modulated charge-doped trilayer nân organic heterojunction with a bidirectional tunable energy band discontinuity is constructed. The rectifying mechanism of the trilayer is similar to the rectifying and inverse-rectifying characteristics from nâp and pân junctions, respectively. Zero-bias optoelectronic behavior and persistent photoconductivity are discovered. These results show that what are viewed as technological hurdles in the development of an organic nân heterojunction should, in fact, lead to a better approach in organic optoelectronics.
The paper reports parametric study, using a molecular dynamicsâcontinuum hybrid simulation method, of liquid flow in micro/nanochannels
with surface nanostructures. The effects of channel height, shape of roughening element, ratio of pitch to length of roughening
element and liquidâsolid bonding strengths (representing surface wettability) on the velocity and temperature boundary conditions
are investigated. The velocity boundary condition is found to shift from significant slip to locking due to the blocking of
the surface nanostructure. The blocking appears weak for small pitch ratio and weak liquidâsolid bonding. Distorted streamlines,
small random eddies and appreciable density oscillations are seen in the vicinity of the wall for small pitch ratio and strong
liquidâsolid bonding. On the other hand, smooth streamlines and weak density oscillations are seen for large pitch ratio and
weak liquidâsolid bonding. Results also reveals that: relative slip length, relative Kapitza length and minus pressure gradient
vary with channel height and pitch ratio in functions of power law and approximately linear, respectively; relative slip and
Kapitza lengths vary with liquidâsolid bonding strength as approximately decreasing power functions (except for the strongest
case), whereas minus pressure gradient varies with liquidâsolid bonding strength as approximately a logarithm-like function.
The effect of shape of roughening element is found to be much less significant compared with the other factors studied.
Content Type Journal Article
Category Research Paper
Pages 1-18
DOI 10.1007/s10404-012-0933-7
Authors
Jie Sun, School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London, E1 4NS UK
Ya Ling He, Key Laboratory of Thermal Fluid Science and Engineering of MOE, State Key Laboratory of Multiphase Flow in Power Engineering, Xiâan Jiaotong University, Xiâan, 710049 Shaanxi, China
Wen Quan Tao, Key Laboratory of Thermal Fluid Science and Engineering of MOE, State Key Laboratory of Multiphase Flow in Power Engineering, Xiâan Jiaotong University, Xiâan, 710049 Shaanxi, China
John W. Rose, School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London, E1 4NS UK
Hua Sheng Wang, School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London, E1 4NS UK
In this work, an experimental investigation of the single- and multiphase flows of two sets of fluids, CO2âethanol and CO2âmethanol, in a non-adiabatic microfluidic T-junction is presented. The operating conditions ranged from 7 to 18 MPa, and
from 294 to 474 K. The feed mass fraction of CO2 in the mixtures was 0.95 and 0.87, respectively. Under these operating conditions, CO2 was either in liquid, gas or supercritical state; and the mixtures experienced a miscible single phase or a vapourâliquid
equilibrium (VLE), with two separated phases. Taylor, annular and wavy were the two-phase flow regimes obtained in the VLE
region. In the single phase region, the observed flows were classified into standard single-phase flows, âpseudoâ two-phase
flows and local phenomena in the T-junction. Flow regime maps were generated, based on temperature and pressure conditions.
Two-phase flow void fractions and several parameters of Taylor flow were analysed. They showed a clear dependency on temperature,
but were mostly insensitive to pressure. A continuous accumulation of liquid, either in the CO2 channel or at the CO2-side wall after the T-junction, disturbed most of the experiments in VLE conditions by randomly generating liquid plugs.
This phenomenon is analysed, and capillary and wetting effects due to local Marangoni stresses are suggested as possible causes.
Content Type Journal Article
Category Research Paper
Pages 1-14
DOI 10.1007/s10404-011-0927-x
Authors
R. Blanch-Ojea, Department of Mechanical Engineering, Rovira i Virgili University, Campus Sescelades, 43007 Tarragona, Spain
R. M. Tiggelaar, Mesoscale Chemical Systems, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
J. Pallares, Department of Mechanical Engineering, Rovira i Virgili University, Campus Sescelades, 43007 Tarragona, Spain
F. X. Grau, Department of Mechanical Engineering, Rovira i Virgili University, Campus Sescelades, 43007 Tarragona, Spain
J. G. E. Gardeniers, Mesoscale Chemical Systems, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
Lab Chip, 2012, Accepted Manuscript DOI: 10.1039/C2LC21304D, Paper
Jeonghun Nam, HyunJung Lim, Dookon Kim, Hyun Wook Jung, Sehyun Shin Pure separation and sorting of microparticles from complex fluids are essential for biochemical analyses and clinical diagnostics. However, conventional techniques require highly complex and expensive labeling processes for high purity... The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, 12,948-953 DOI: 10.1039/C2LC20939J, Paper
Debaditya Choudhury, William T. Ramsay, Robert Kiss, Nicholas A. Willoughby, Lynn Paterson, Ajoy K. Kar An integrated multichannel microfluidic cell separation device enabled using ultrafast laser inscription and selective chemical etching. The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, 12,954-959 DOI: 10.1039/C2LC21020G, Paper
Matthew R. Leyden, Robert J. Messinger, Canan Schuman, Tal Sharf, Vincent T. Remcho, Todd M. Squires, Ethan D. Minot We quantify the rate that proteins bind to a nanoelectronic biosensor and increase this rate by blocking upstream binding sites. The content of this RSS Feed (c) The Royal Society of Chemistry
Seila Selimovic, Ali Khademhosseini Self-assembled curved microdevices - Immunomagnetic hooks for capturing circulating tumor cells - Microfluidics for geological studies The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Advance Article DOI: 10.1039/C2LC21133E, Paper
Amit V. Desai, Joshua D. Tice, Christopher A. Apblett, Paul J. A. Kenis We present an analytical model to guide the design of electrostatic microvalves that can be integrated into microfluidic chips using standard fabrication processes and can reliably operate at low actuation potentials (<250 V). To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Advance Article DOI: 10.1039/C2LC20906C, Paper
Alar Ainla, Gavin D. M. Jeffries, Ralf Brune, Owe Orwar, Aldo Jesorka A multifunctional solution handling and dispensing tool, using hydrodynamically confined flow, to deliver solutions in a contamination free manner within single cell environments. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, 12,916-922 DOI: 10.1039/C2LC20971C, Paper
Tobias W. Hofmann, Siegfried Hanselmann, Jan-Wilhelm Janiesch, Anne Rademacher, Christian H. J. Bohm We present a novel sensor method which exploits changes in the size of microdroplets driven by osmotic pressure differences as a label-free marker for reactions inside the droplets. The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, 12,901-905 DOI: 10.1039/C2LC20922E, Paper
Karthik Reddy, Yunbo Guo, Jing Liu, Wonsuk Lee, Maung Kyaw Khaing Oo, Xudong Fan We integrated four ultra-sensitive Fabry-Perot vapor sensors on a single chip for vapor discrimination in micro-gas chromatography applications. The content of this RSS Feed (c) The Royal Society of Chemistry
A. Lenshof, M. Evander, T. Laurell, J. Nilsson This tutorial covers some of the basics in designing and building microfluidic acoustic resonators and will hopefully be a comprehensive and advisory document to assist the interested reader in creating a successful acoustophoretic device. The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, 12,939-947 DOI: 10.1039/C2LC20931D, Paper
Tilak Jain, Adrian Papas, Amol Jadhav, Ryan McBride, Enrique Saez Method development towards a miniaturized platform for HTS siRNA screening in mammalian cells. The content of this RSS Feed (c) The Royal Society of Chemistry
We present new passive microfluidic mixing structures based on 2D and 3D geometries. The primary mechanism of mixing in these
devices is based on chaotic advection. The mixers which incorporate 3D structures introduce transverse flow rotation greatly
enhancing performance. Simulations and experimental tests were performed over a Reynolds number (Re) range from 0.1 to 20
and showed good agreement. At an Re of 0.1, 90% mixing was achieved in a path length of 32 and 7 mm, for the 2D and 3D geometrical
mixers, respectively. This represents an improvement in performance over a standard T-mixer of 20% for the 2D mixer and 82.5%
for the 3D mixer. An inflection point in the mixing efficiency was observed for both mixer types around an Re of 1. The devices
were fabricated on a polymethylmethacrylate (PMMA) substrate, using an excimer laser beam incorporating an intelligent pinhole
mask. Initially, structures were developed off-line using a laser simulation tool. A design-of- experiments (DOE) approach
along with computational fluid dynamic (CFD) analysis was used to optimise mixing element geometry. This precursor to the
fabrication step greatly reduces the time between the design stage and device realisation.
Content Type Journal Article
Category Research Paper
Pages 1-11
DOI 10.1007/s10404-011-0928-9
Authors
Kevin Conlisk, National Centre for Laser Applications, School of Physics, National University of Ireland, Galway, University Road, Galway, Ireland
Gerard M. OâConnor, National Centre for Laser Applications, School of Physics, National University of Ireland, Galway, University Road, Galway, Ireland
This paper describes the optical and hydrodynamic characteristics of particle motion in a cross-type optical particle separator.
The retention distance modulated by the optical force on a particle was measured in three dimensions for various vertical
and horizontal positions via Îź-defocusing digital particle image velocimetry. The experimental data showed that the actual
retention distance was smaller than the predicted retention distance under the assumption that the approaching velocity was
constant through the cross-section of a microfluidic channel. The retention distance was shown to increase as the injection
position of the particle shifted toward the channel side wall at a given vertical position due to a higher residence time
within the region of influence of the laser beam. In contrast, the retention distance decreased as the injection position
shifted toward the channel top/bottom walls at a given horizontal position. A theoretical modeling study was conducted to
support and interpret the experimental measurements. The resolution of the particle separation procedure, which did not require
adjusting the flow rate, laser power, or working fluid properties, was studied.
Content Type Journal Article
Category Research Paper
Pages 1-9
DOI 10.1007/s10404-012-0935-5
Authors
Kang Soo Lee, Department of Mechanical Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701 Korea
Sang Youl Yoon, Department of Mechanical Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701 Korea
Sang Bok Kim, Department of Mechanical Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701 Korea
Kyung Heon Lee, Department of Mechanical Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701 Korea
Hyung Jin Sung, Department of Mechanical Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701 Korea
Sang Soo Kim, Department of Mechanical Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701 Korea
Lab Chip, 2012, 12,923-931 DOI: 10.1039/C2LC20917A, Paper
Wei-Feng Fang, Shang-Chieh Ting, Ching-Wen Hsu, Yu-Tzu Chen, Jing-Tang Yang We report a novel technique that achieves a locally enhanced concentration of DNA at the rear of a free-solution plug in a plug-based microfluidic device. The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Advance Article DOI: 10.1039/C2LC21114A, Paper
Hsin-I Peng, Christopher M. Strohsahl, Benjamin L. Miller Uniform coating of Ag nanoparticles leads to a rapid, arrayble and self-labelled microfluidic device able to detect DNA in real time. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
DNA computing is a promising approach for dealing with biomolecular information. Although several DNA logic circuits which
can evaluate biomolecular inputs have been proposed, they have serious drawbacks in the processing speed and the amount of
molecules used in implementation. Here, we present optofluidic DNA computation as an effective method for constructing a DNA
computing system. By confining the reaction space of DNA computation to the inside of a microdroplet and manipulating a group
of droplets with external light signals, we improve usability of DNA computation as well as the processing performance. Optical
manipulation is applied to transport the droplets and to initiate DNA computation by forced merging of the droplets. The proposed
method has advantages over conventional DNA computation schemes in flexible operations, simultaneous multiplexed evaluation,
and processing acceleration. As the first demonstration of optofluidic DNA computation, logical AND and OR operations are
performed by optical manipulation of microdroplets which contain either DNA logic gates or input molecules. Also, considerable
reduction in the processing time is confirmed on the optofluidic DNA computation owing to reduction of the reaction space
to the microdroplet.
Content Type Journal Article
Category Research Paper
Pages 1-7
DOI 10.1007/s10404-012-0934-6
Authors
Takahiro Nishimura, Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Suita,, Osaka, Japan
Yusuke Ogura, Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Suita,, Osaka, Japan
Jun Tanida, Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Suita,, Osaka, Japan
Enzyme-activated prodrugs have been investigated and sought after as highly specific, low-side-effect treatments, especially for cancer therapy. Unfortunately, excellent targets for enzyme-activated therapy are rare. Here a system based on cell delivery that can carry both a prodrug and an activating enzyme to the cancer site is demonstrated. Raw264.7 cells (mouse monocyte/macrophage-like cells, Mo/Ma) are engineered to express intracellular rabbit carboxylesterase (InCE), which is a potent activator of the prodrug irinotecan to SN38. InCE expression is regulated by the TetOnÂŽ system, which silences the gene unless a tetracycline, such as doxycycline, is present. Concurrently, an irinotecan-like prodrug, which is conjugated to dextran and can be loaded into the cytoplasm of Mo/Ma, is synthesized. To test the system, a murine pancreatic cancer model is generated by intraperitoneal (i.p.) injection of Pan02 cells. Engineered Mo/Ma are loaded with the prodrug and are injected i.p. Two days later, doxycycline was given i.p. to activate InCE, which activated the prodrug. A survival study demonstrates that this system significantly increased survival in a murine pancreatic cancer model. Thus, for the first time, a prodrug/activating enzyme system, which is self-contained within tumor-homing cells and can prolong the life of i.p. pancreatic tumor bearing mice, is demonstrated.
Monocyte/macrophage-like cells (Raw264.7) are shown to migrate specifically to intraperitoneal tumors when injected intraperitoneally. These cells can be engineered to express a TetOnÂŽ regulated intracellular carboxylesterase, loaded with an irinotecan-like prodrug, and used to deliver and activate the prodrug specifically at a tumor site when given with doxycycline.
Delineation of tumor margins is a critical and challenging objective during brain cancer surgery. A tumor-targeting deep-blue nanoparticle-based visible contrast agent is described, which, for the first time, offers in vivo tumor-specific visible color staining. This technology thus enables color-guided tumor resection in real time, with no need for extra equipment or special lighting conditions. The visual contrast agent consists of polyacrylamide nanoparticles covalently linked to Coomassie Blue molecules (for nonleachable blue color contrast), which are surface-conjugated with polyethylene glycol and F3 peptides for efficient in vivo circulation and tumor targeting, respectively.
Hydrogel nanoparticles containing a high concentration of visible dye by covalent linkage, with PEGylated surface and conjugated tumor targeting moiety, enable visual delineation of brain tumors in vitro and in vivo. This technology enables color-guided tumor resection in real time, with no need for extra equipment or special lighting conditions.
Sonochemically formed metal capsules, which can protect a metal surface and release active compounds, are presented. The capsules are formed by modifying a metal surface into having a porous sponge layer; this layer is continuous with the bulk metal allowing for excellent adhesion. The porosity of the sponge layer and polyelectrolyte complexes allows active compounds to be stored and released depending on external stimuli. These porous capsules open up prospects in metal nanoengineering and surface protection as well as in encapsulation and polyelectrolyte applications.
An approach is developped to gain control over the polarity of neuronal networks at the cellular level by physically constraining cell development by the use of micropatterns. It is demonstrated that the position and path of individual axons, the cell extension that propagates the neuron output signal, can be chosen with a success rate higher than 85%. This allows the design of small living computational blocks above silicon nanowires.
A reliable nanofabrication concept to engineer metallic nanometric gap structures and to incorporate silver nanoparticles within the gaps utilizing a combination of self-assembly strategies and electrochemical oxidation lithography is developed. The approach uses the differences in oxidation kinetics of n-octadecyltrichlorosilane (OTS) monolayer and bilayer structures. The processes are investigated in detail and form the basis for a new nanofabrication process.
Nanomaterials with vectoral electromagnetic properties have potential applications in solar cells, plasmonic cavity resonators, light polarizers, and biosensing. Here a new, simple, solution-based method for producing nanomaterials comprising vertically aligned standing arrays of gold nanorods (NRs) end-functionalized with polymer ligands is reported. The method utilizes the side-by-side assembly of the NRs into large 2D superlattices, followed by the precipitation of the lattices on a solid substrate. The critical design rules for the self-assembly of superlattices are demonstrated, and they show the generality of the method by forming standing arrays from the NRs end-tethered with poly(N-vinylcarbazole) or with polystyrene molecules.
Solution-based side-by-side assembly of 2D superlattices of gold nanorods end-functionalized with a small amount of polymer paves the way for producing standing nanorod arrays.
A mild, facile one-step synthetic strategy for the preparation of size- and shape-controlled silver nanoparticles (AgNPs) is presented. The high degree of size- and shape-control of these AgNPs is achieved by the use of triazole sugar ligands scaffolded by a central resorcinol ether core. Both the triazoles and the resorcinol ether core mediate the nucleation, growth, and passivation phases of the preparation of AgNP in the presence of the Tollens reagent as the silver source. Kinetic and 1H NMR titration data is presented describing the nature of the interactions between the Tollens reagent and these ligands.
A mild, facile one-step synthetic strategy for the preparation of size- and shape-controlled silver nanoparticles (AgNPs) is presented. The AgNPs prepared by this strategy exhibit remarkable stability in high salt aqueous buffer systems up to 2.8 M NaCl for a period of at least 24 h. The high degree of size- and shape-control of these AgNPs is achieved by the development of novel multifunctional triazole sugar ligands, which mediate the nucleation, growth, and passivation phases of AgNP preparation in the presence of the Tollens reagent as the silver source.
In biomedical applications, polyethylene glycol (PEG) functionalization has been a major approach to modify nanocarriers such as nano-graphene oxide for particular biological requirements. However, incorporation of a PEG shell poses a significant diffusion barrier that adversely affects the release of the loaded drugs. This study addresses this critical issue by employing a redox-responsive PEG detachment mechanism. A PEGylated nano-graphene oxide (NGO-SS-mPEG) with redox-responsive detachable PEG shell is developed that can rapidly release an encapsulated payload at tumor-relevant glutathione (GSH) levels. The PEG shell grafted onto NGO sheets gives the nanocomposite high physiological solubility and stability in circulation. It can selectively detach from NGO upon intracellular GSH stimulation. The surface-engineered structures are shown to accelerate the release of doxorubicin hydrochloride (DXR) from NGO-SS-mPEG 1.55 times faster than in the absence of GSH. Confocal microscopy shows clear evidence of NGO-SS-mPEG endocytosis in HeLa cells, mainly accumulated in cytoplasm. Furthermore, upon internalization of DXR-loaded NGO with a disulfide-linked PEG shell into HeLa cells, DXR is effectively released in the presence of an elevated GSH reducing environment, as observed in confocal microscopy and flow cytometric experiments. Importantly, inhibition of cell proliferation is directly correlated with increased intracellular GSH concentrations due to rapid DXR release.
A PEGylated nano-graphene oxide (NGO-SS-mPEG) with redox-responsive polyethylene glycol (PEG) detachment mechanism can rapidly release encapsulated payload under tumor-relevant glutathione (GSH) levels. The specially engineered delivery system addresses the critical issues related to NGO of physiological stability and drug delivery in a tumor-selective and controlled fashion.
The formation of ligand-protected gold nanoclusters during size-selective syntheses is seemingly driven by the inherent properties of the protecting ligands, but a general description of the product formation has not been presented. This study uses diphosphine-protected Au clusters as a model system to examine i) control of metal-ligand complex distributions in methanolâchloroform solutions, ii) role of solution perturbations, e.g., oxidation, and iii) nanocluster formation through reduction of characterized complex distributions. By selectively reducing complexes and monitoring cluster formation with electrospray ionization mass spectrometry and UVâvis, data show the distribution of complexes can be controlled through ligand exchange, and the reduction of specific complexes produce characteristic ligated gold clusters based on ligand class. Specifically, 1,n-bis(diphenylphosphino)n-alkane ligands, Ln, where n = 1 through 6, are classified into two distinct sets. The classes represent ligands that either form mainly [AuLn2]+ (Class I, n = 1â3) or bridged [Au2Ln2]2+ (Class II, n = 4â6) complexes after complete ligand exchange with AuClPPh3. Selectively reducing gold-phosphine ligand complexes allows mapping of product formation, resulting collectively in a predictive tool for ligated gold cluster production by simply monitoring the initial complex distribution prior to reduction.
Selective reduction of gold-diphosphine complexes produces predictable nascent gold nanoclusters that can be separated into two classes. Class I complexes produce nascent neutral clusters and Class II produce cationic, ligated Au8 and Au10 nanoclusters. Predictable nascent products allow further tunable control of metal nuclearity through postreduction, size-selective processing, when desired.
Methods for combining multiple functions into well-defined nanomaterials are still lacking, despite their need in nanomedicine and within the broader field of nanotechnology. Here several strategies for controlling the amount and the ratio of combinations of labeled DNA on 13-nm gold nanoparticles using self-assembly of thiolated DNA and/or DNA-directed assembly are explored. It is found that the self-assembly of mixtures of fluorescently labeled DNA can lead to a higher amount of labeled DNA per particle; however, the ratio of fluorophores on the nanoparticles differs greatly from that in the self-assembly solution. In contrast, when fluorescently labeled DNA are hybridized to DNA-modified gold nanoparticles, the fluorophore ratio on the nanoparticles is much closer to their ratio in solution. The use of bifunctional DNA-doublers in self-assembly and DNA-directed assembly is also explored to increase the complexity of these materials and control their composition. Finally, tuning the distance between the labels from 2.9 to 5.4 nm was achieved using different hybridized DNA clamp complexes. Fluorescent results suggest that assembling these clamps on nanoparticle surfaces may be possible, although the resulting label spacing could not be quantified.
Strategies for controlling the composition and loading of multiple functional groups on DNA-modified gold nanoparticles are compared using fluorescence spectroscopy, different DNA constructs, and fluorophore small-molecule labels. To dial in distances between the fluorophores, hybridization of an adjuster strand to branched DNA or Y-DNA complexes is shown to further modulate supramolecular spacing.
A simple reaction between a mild reducing agent such as a trialkoxysilane and GeIV species such as germanium tetraalkoxides in a room-temperature water/alcohol solution produces silica-coated ultrasmall (2â3 nm) amorphous germanium nanoparticles (na-Ge/SiO2). The initial reaction involves the straightforward hydrolysis and condensation of the precursors, Ge(OCH2CH3)4 and (CH3CH2O)3SiH, where the reaction rate depends on the water concentration in the reaction medium. These processes can be further accelerated by adding acid to the reaction medium or carrying out the reaction at higher temperatures. At low water contents (up to 50% water/ethanol) and low acid concentrations, the reaction proceeds as a clear solution, and no precipitation is observed. The initially colorless clear solution progressively changes to pale yellow, yellow, orange, red, and finally dark red as the na-Ge particles grow. Evaporation of the solvent yields a reddish-brown powder/monolith consisting of na-Ge, embedded in an encapsulating amorphous silica matrix, na-Ge/SiO2. The formation of na-Ge proceeds extremely slowly and follows a first-order dependence on both water concentration and diameter of the na-Ge particles under the reaction conditions used. Annealing of the na-Ge/SiO2 powder under an inert atmosphere at 600 °C produces ultrasmall germanium nanocrystals (nc-Ge) embedded in amorphous silica (nc-Ge/SiO2). Freestanding, colloidally stable nc-Ge is obtained by chemical etching of the encapsulating silica matrix.
Two oxide-based precursors in a water/alcohol solution, one acting as a reducing agent ((CH3CH2O)3SiH) and the other as a germanium source (Ge(OCH2CH3)4), react very slowly to form colloidally stable amorphous nanoparticles of germanium encapsulated by a shell of silica (na-Ge/SiO2). Evaporation of the solvent yields monoliths of na-Ge/SiO2, which can be annealed to form nanocrystalline germanium (nc-Ge) embedded in a silica matrix (nc-Ge/SiO2), from which free-standing, colloidally stable nc-Ge can be obtained by chemical etching of the encapsulating silica matrix.
Nanotubes from pore-spanning membranes: a site-specific experimental procedure is introduced that allows determination of the lateral tension and bending modulus of pore-spanning bilayers in a single force cycle comprising indentation followed by nanotube formation upon retraction. With this technique, a quantitative mapping of intrinsic local elastic properties comes into reach.
A method for replica molding electrospun (ES) fibers on the surface of polydimethylsiloxane (PDMS) is developed for culturing and guiding of cells, instead of ES fibers. With this method, microgrooves and microstructures composed of microgrooves can be obtained. PDMS is integrated into the microfluidic chip as a substrate to successfully pattern and guide neurites on the PDMS surface with microgrooves.
Binary assemblies of CdSe/CdS semiconductor nanorods are prepared with spherical metal nanoparticles intercalated into aligned, parallel nanorod arrays. Mechanistic studies suggest that the formation of these binary assemblies is a kinetically limited process. Organic additives with suitable polarity and strong affinity to spherical nanoparticles that have both a high dielectric constant and a large Hamaker constant play an important roles.
Lab Chip, 2012, Advance Article DOI: 10.1039/C2LC21113K, Paper
Huaibin Zhang, Shuai Nie, Candice M. Etson, Raymond M. Wang, David R. Walt We present a method for sealing high-density arrays of femtoliter-sized aqueous reaction chambers with a droplet of oil. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Advance Article DOI: 10.1039/C2LC21096G, Paper
Barbara Uszczynska, Tomasz Ratajczak, Emilia Frydrych, Hieronim Maciejewski, Marek Figlerowicz, Wojciech T. Markiewicz, Marcin K. Chmielewski The CuAAC reaction was applied as the novel method of DNA immobilization on a modified solid support. The click reaction enables the covalent binding of DNA modified with pentynyl groups at its 50-end to azide-loaded slides. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
Colorimetric detection of analytes using gold nanoparticles along with surface-enhanced Raman spectroscopy (SERS) are areas of intense research activity since they both offer sensing of very low concentrations of target species. Multimodal detection promotes the simultaneous detection of a sample by a combination of different techniques; consequently, surface chemistry design in the development of multimodal nanosensors is important for rapid and sensitive evaluation of the analytes by diverse analytical methods. Herein it is shown that nanoparticle size plays an important role in the design of functional nanoparticles for colorimetric and SERS-based sensing applications, allowing controlled nanoparticle assembly and tunable sensor response. The design and preparation of robust nanoparticle systems and their assembly is reported for trace detection of Ni(II) ions as a model system in an aqueous solution. The combination of covalently attached nitrilotriacetic acid moieties along with the L-carnosine dipeptide on the nanoparticle surface represents a highly sensitive platform for rapid and selective detection of Ni(II) ions. This systematic study demonstrates that significantly lower detection limits can be achieved by finely tuning the assembly of gold nanoparticles of different core sizes. The results clearly demonstrate the feasibility and usefulness of a multimodal approach.
Design of functionalized gold nanoparticles and their assembly for SERS/colorimetric detection of Ni(II) is described. This systematic study emphasizes the importance of the nanoparticle core size in controlled particle assembly and sensor-response tunability, demonstrating how lower detection limits can be achieved by carefully selecting the particle core size and surface chemistry, promoting the feasibility of a multimodal approach.
An electronic conductance with small fluctuations, which is stipulated in single-molecule junctions, is necessary for the precise control of single-molecule devices. However, the suppression of conductance fluctuations in conventional molecular junctions is intrinsically difficult because the fluctuations are related to the contact fluctuations and molecular motion. In the present study involving experimental and theoretical investigations, it is found that covering a single Ď-conjugated wire with an Îą-cyclodextrin molecule is a promising technique for suppressing conductance fluctuations. The conductance histogram of the covered molecular junction measured with the scanning tunneling microscope break-junction technique shows that the conductance peak for the covered junction is sharper than that of the uncovered junction. The covering technique thus has two prominent effects: the suppression of intramolecular motion, and the elimination of intermolecular interactions. Theoretical calculations of electronic conductance clearly support these experimental observations.
Covering a single Ď-conjugated wire with an Îą-cyclodextrin molecule is a promising technique for suppressing conductance fluctuations. The peak in the conductance histogram of the covered molecular junction is sharper than that of the uncovered junction. The covering technique has two prominent effects: the suppression of intramolecular motion, and the elimination of intermolecular interactions.
A cationic polythiopheneâporphyrin (PTP) dyad is shown to exhibit efficient light-activated antifungal activity. Higher singlet oxygen (1O2) generation efficiency can be attained from PTP upon photoexcitation due to the light-harvesting properties of the polymer backbone and efficient energy transfer from the polythiophene to the porphyrin units. PTP can be used for treating fungal infections in lower doses of irradiation light and polymer concentration.
Type II and quasi-type II nanocrystals with thick shells exhibit reduced blinking. However, after a number of monolayers, the influence of the shell thickness is found to vanish. Using a two-band Kane Hamiltonian, it is shown that this behavior is a consequence of interband coupling and asymmetric confinement of electrons and holes. Interface alloying provides an additional, order-of-magnitude contribution to the Auger suppression, in agreement with recent experiments. The existence is predicted of critical shell thicknesses that strongly quench Auger processes for any core size.
Core/shell nanocrystals in which electrons and holes have different spatial locations display reduced Auger relaxation rates. A two-band Kane Hamiltonian is used to understand the observed experimental behavior. It is shown that certain shell thicknesses lead to strongly suppressed Auger recombination, regardless of the core size.
Old chemistry for novel materials: Self-fluorescent high-relaxivity T2-weighted magnetic resonance imaging (MRI) contrast agents are produced. They are a novel type of MR/optical dual-modality in vivo imaging nanoprobe using glutaraldehyde crosslinking chemistry, and they are used to label and monitor therapeutic cells both in vitro and in vivo.
A simple approach is developed to identify the layer number of 2D MoS2 sheets. By using an optical imaging method combined with image analysis software, a high-contrast image of the MoS2 sheets can be extracted from the red (R) channel of the color optical microscopy image. The value of the intensity difference in the grayscale image of the R channel between MoS2 sheets (1â3 layers) and the SiO2 substrate can be used to identify the layer number of the sheet.
The direct observation of drug release from carbon nanotube vehicles in living cells is realized through a unique two-dye labeling approach. Single-walled carbon nanotubes (SWNTs) are firstly marked with fluorescein isothiocyanate (FITC) to track their location and movement inside the cell. Then a fluorescent anticancer drug doxorubicin (DOX) is attached by means of Ď-stacking onto SWNTs. Delivered by SWNTs into cells, DOX will detach from the vehicle in an acidic environment due to the pH-dependent ĎâĎ stacking interaction between DOX and SWNTs. From observation of the two different kinds of fluorescence (green and red) that respectively represent the carrier SWNTs and drug DOX, the process of drug release inside the living cell can be monitored under a confocal microscope. Results show that the drug DOX detaches from SWNTs inside the lysosomes to yield free molecules and escape into the cytoplasm and finally into the nucleus, while the vehicle SWNTs are trapped inside the lysosomes, without entering the nucleus. The current observations confirm previously proposed mechanisms for drug/DOX release inside cells. The experimental establishment of drug-release mechanisms in living cells here might provide important insights for future design of new drug-delivery and release systems.
The subcellular release of anticancer drug DOX from carbon nanotube vehicles in living cells is directly observed under a confocal microscope using a unique two-dye labeling approach. Imaging clearly shows the time-dependent process of drug transportation into cells and release to the cell nucleus. The drug DOX detaches from SWNTs inside the lysosomes to yield free molecules to escape into the cytoplasm and finally into the cell nucleus, while the vehicle SWNTs are trapped inside lysosomes, without entering the nucleus.
Lab Chip, 2012, Advance Article DOI: 10.1039/C2LC21116E, Paper
Lorenzo Amato, Yu Gu, Nicola Bellini, Shane M. Eaton, Giulio Cerullo, Roberto Osellame Integration of a size-based three-dimensional filter, with micrometre-sized pores, in an already sealed commercial microfluidic chip by two-photon polymerization. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
Lab Chip, 2012, Advance Article DOI: 10.1039/C2LC21097E, Paper
Yen-Heng Lin, Ya-Wen Yang, Yi-Dao Chen, Shih-Siou Wang, Yu-Han Chang, Min-Hsien Wu The application of an optically switched dielectrophoretic (ODEP) force in a microfluidic perfusion cell culture system for bottom-up tissue engineering. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
Well-defined metallic nanobowls can be prepared by extending the concept of a protecting group to colloidal synthesis. Magnetic nanoparticles are employed as âprotecting groupsâ during the galvanic replacement of silver with gold. The replacement reaction is accompanied by spontantous dissociation of the protecting groups, leaving behind metallic nanobowls.
A practical open channel microfluidic reactor with immobilized palladium complex was built on a cyclic olefin copolymer (COC)
chip that was fabricated with a very simple hot-embossing technique. Palladium complex was immobilized on a photochemically
grafted layer of polymerized N-[3-(dimethylamino)propyl]methacrylamide. Surface modification and catalyst immobilization onto COC were systematically characterized
with streaming potential, surface contact angle, attenuated total reflection Fourier transform infrared spectrometry, scanning
electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. The reactor was comprised of a single 15 cm
long serpentine channel of 120 Îźm (i.d.) and exhibited high efficiency for the Suzuki cross-coupling reaction of aryl iodides
and bromides with arylboronic acids, affording good to excellent yields of the corresponding products. The reactions could
be carried out smoothly with reduced reaction time and lower reactant consumption in the microreactor thermostated at 50°C.
The proposed system may have great potential for high-throughput screening of catalysts and reaction conditions.
Content Type Journal Article
Category Research Paper
Pages 1-9
DOI 10.1007/s10404-011-0932-0
Authors
Hongling Li, State Key Laboratory of Applied Organic Chemistry, Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province, Department of Chemistry, Lanzhou University, Lanzhou, 730000 Gansu, China
Xiaotong Gao, State Key Laboratory of Applied Organic Chemistry, Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province, Department of Chemistry, Lanzhou University, Lanzhou, 730000 Gansu, China
Hui Ding, State Key Laboratory of Applied Organic Chemistry, Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province, Department of Chemistry, Lanzhou University, Lanzhou, 730000 Gansu, China
Min Yang, National Engineering Research Center for Fine Petrochemical Intermediates, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000 Gansu, China
Qiaosheng Pu, State Key Laboratory of Applied Organic Chemistry, Key Laboratory of Nonferrous Metals Chemistry and Resources Utilization of Gansu Province, Department of Chemistry, Lanzhou University, Lanzhou, 730000 Gansu, China
A lot of production processes involve mixing steps. The understanding of fluid flows in mixing processes of liquid components
is needed in order to develop appropriate mixers for the chemical and pharmaceutical industry. Especially mixing in microfluidic
systems is a challenge due to the diffusion-based processes. A multi-lamination micromixer with chessboard outlet geometry
is used to induce the mixing process. To get comprehensive information about the mixing process, the velocity profile of the
fluid flow and the species concentration distribution during the mixing process should be measured. Thus, we have combined
particle image velocimetry (PIV) and Raman scattering. To enable rapid detection, the Raman imaging mode is used to visualise
the concentration distribution. By this setup light sheets along and orthogonal to the outlet of the micromixer are recorded
and synchronized with PIV measurement. As a model system we have used water and ethanol/methanol, enabling a selective monitoring
of the substances by choosing appropriate spectral areas. The PIV is recorded based on Mie scattering and fluorescence using
microsphere tracers. In this study, we present a setup for determination of the velocity profile field and the spatial concentration
distribution of water and ethanol/methanol in a micromixer.
GĂźnter Rinke, Karlsruhe Institute of Technology (KIT), Institute for Micro Process Engineering, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
Convenient for both biologists and MEMS designers, Polydimethylsiloxane (PDMS) polymer is intensively investigated for its
biocompatibility, transparency, high resistance under plasma treatment, flexibility and resistance to high temperature. However,
for microfluidic applications, the fabrication of PDMS circular channels is difficult to achieve except by wire moulding.
In this article, we present a simple, fast and low-cost fabrication method which can be applied out of clean-room environment.
It is based on the deposition of alginic acid sodium salt aqueous solution, enabling the formation of a liquid cylinder on
the most hydrophilic part of a hydrophilic/hydrophobic patterned surface. We experimentally studied the interaction between
liquid rivulets and surfaces presenting a contrast of wettability and/or a stepwise texture. Subsequent moulding of the half-cylinder
of liquid produces round PDMS microfluidic channels. The optimal parameters for hydrophilic/hydrophobic patterns have then
been applied to produce the roundest possible channels. The realisation of both straight channels 300â500 Îźm wide, 1 cm long
and 75° tangent chord angle at best, and Y-shaped channels with the same dimensions and 55° TCA is demonstrated.
Content Type Journal Article
Category Research Paper
Pages 1-9
DOI 10.1007/s10404-011-0929-8
Authors
Magalie De Ville, Institut dâElectronique, de MicroĂŠlectronique et de Nanotechnologie, CNRS UMR 8520, Avenue PoincarĂŠ, 59658 Villeneuve dâAscq, France
Philippe Coquet, Institut dâElectronique, de MicroĂŠlectronique et de Nanotechnologie, CNRS UMR 8520, Avenue PoincarĂŠ, 59658 Villeneuve dâAscq, France
Philippe Brunet, Institut dâElectronique, de MicroĂŠlectronique et de Nanotechnologie, CNRS UMR 8520, Avenue PoincarĂŠ, 59658 Villeneuve dâAscq, France
Rabah Boukherroub, Institut dâElectronique, de MicroĂŠlectronique et de Nanotechnologie, CNRS UMR 8520, Avenue PoincarĂŠ, 59658 Villeneuve dâAscq, France
The literature includes a variety of analytical and semi-analytical models to describe squeeze-film damping in MEMS perforated
structures. Even if many of them have been validated by means of numerical simulations, nobody seems to have discussed about
the accuracy of numerical approaches in this field. In the present paper, we apply both the main analytical models and a commercial
finite element software, COMSOL Multiphysics, to solve a good number of squeeze-film problems. They refer to some cases, which
were experimentally investigated during the past by different authors. The tested structures are rigid rectangular plates
fabricated with different material, different perforation ratio (i.e., the ratio of the hole side to the holes pitch) and
different number of perforations. We compare both the analytical and the numerical results with the available experimental
data, in order to have an overview about their effectiveness. Numerical simulations offer in all the considered cases valuable
agreement with experiments.
Content Type Journal Article
Category Research Paper
Pages 1-9
DOI 10.1007/s10404-011-0931-1
Authors
Salvatore Nigro, Department of Medical Sciences, University Magna Graecia, Viale Europa, 88100 Germaneto, Italy
Leonardo Pagnotta, Department of Mechanical Engineering, University of Calabria, Ponte P. Bucci, 44C, 87036 Rende, Italy
Maria F. Pantano, Department of Mechanical Engineering, University of Calabria, Ponte P. Bucci, 44C, 87036 Rende, Italy
Ribonucleic acid (RNA) is proposed as a nonionic surfactant for the efficient exfoliation of graphite in thin flakes of few-layer graphene and the subsequent preparation of transparent and conducting thin films. Parameters such as the type of RNA used and the size of starting graphite flakes are demonstrated to be essential for obtaining RNAâgraphene thin films of good quality. A model explaining the exfoliation of graphene by RNA in water is suggested. A number of post- and predeposition treatments (including thermal annealing, functionalization of the films, and the preoxidation of graphite) are critical to improve the performance of grapheneâRNA nanocomposites as transparent conductors. The study establishes an ideal link between RNA and graphene, the fundamental building blocks for nanobiology and carbon-based nanotechnology.
Different mechanisms of adhesion occur on graphene surfaces for the two types of RNA investigated: RNA VI forms aggregates whereas RNA IX uniformly covers the graphene surface. Such differences lead to the formation of different types of transparent and conducting grapheneâRNA composites, with the best crossover between transparency and electric performance for nanocrystalline graphite dispersed in RNA VI.
Layer-by-layer assembly (LbL) is a rich, versatile, and powerful technique for fabricating multilayer thin films with controlled architecture and functions. Singly charged, uncharged, or water-repellent molecules cannot be used directly in conventional LbL assembly. This problem can be solved with unconventional LbL methods, by employing the preassembly of building blocks in solution and the use of these assemblies for LbL formation at the interface. This Concept summarizes different methods of unconventional LbL assembly, including electrostatic complex formation, hydrogen-bonded complexes, block-copolymer micelles, and ĎâĎ interaction complexes. These preassembly treatments endow the building blocks with enhanced abilities for advanced functionality, in particular, surface molecular imprinting, a new concept emerging from unconventional LbL. Molecular imprinting approaches are thus conceptually described based on different types of interactions and their great potential in applications is demonstrated by examples such as selective surface patterning and selective filtration.
Preassembling singly charged, uncharged, or water-repellent building blocks in an unconventional layer-by-layer fashion enhances the ability for advanced functionality, in particular, surface molecular imprinting, of the resulting multilayer film.
The interaction of proteins with ultrasmall gold nanoclusters (Au NCs) is investigated. Upon protein association, the fluorescence of Au NCs is significantly enhanced and, concomitantly, their luminescence lifetime is prolonged. The results stress the importance of investigating the behavior of fluorescent metal NCs in complex biological environment for advancing their bio-nanotechnology applications.
Microfluidic systems have been extensively applied in research of chemistry, biology and fluidic dynamics. In these applications,
local and precise measurements are often crucial for reliable results. We demonstrate here a multilayered, multifunctional
microfluidic platform with embedded electrodes open to the microchannel and thermocouple sensors underneath the microchannel
that are suitable for local electrical and thermal measurements, respectively. We demonstrate that precise transport measurements
with ac excitation frequency up to 1 MHz can be performed for electrolytes in centimeter-long microchannels. Local temperature
sensing of the fluids in the microchannels can also be performed on this system. Such system can be either used to characterize
local electrical and thermal properties of fluids, or applied to the study of thermal related electrokinetic phenomena, such
as joule heat generation in dc conductance or temperature dependence of electrical transport.
Content Type Journal Article
Category Research Paper
Pages 1-8
DOI 10.1007/s10404-011-0930-2
Authors
Qianwei Zhuang, Department of Electronics, Key Laboratory for the Physics and Chemistry of Nanodevices, Peking University, Beijing, 100871 Peopleâs Republic of China
Weiqiang Sun, Department of Electronics, Key Laboratory for the Physics and Chemistry of Nanodevices, Peking University, Beijing, 100871 Peopleâs Republic of China
Yilin Zheng, Department of Electronics, Key Laboratory for the Physics and Chemistry of Nanodevices, Peking University, Beijing, 100871 Peopleâs Republic of China
Jiongwei Xue, Department of Electronics, Key Laboratory for the Physics and Chemistry of Nanodevices, Peking University, Beijing, 100871 Peopleâs Republic of China
Haixiao Liu, Department of Electronics, Key Laboratory for the Physics and Chemistry of Nanodevices, Peking University, Beijing, 100871 Peopleâs Republic of China
Mo Chen, Department of Electronics, Key Laboratory for the Physics and Chemistry of Nanodevices, Peking University, Beijing, 100871 Peopleâs Republic of China
Shengyong Xu, Department of Electronics, Key Laboratory for the Physics and Chemistry of Nanodevices, Peking University, Beijing, 100871 Peopleâs Republic of China
The fabrication of thin organic films covalently grafted onto silicon substrates is of significant interest, as they are expected to give access to a broad range of new materials for integration into microelectronic applications. Covalent layer-by-layer (LbL) assembly offers a high degree of freedom when designing such thin films. In this work an approach for the preparation of covalent redox active molecular multilayers on silicon (100) surfaces is presented using a highly branched decaallylferrocene and thiol-ene click chemistry. The multilayers are analyzed by ellipsometry, X-ray photoelectron sprectroscopy, and cyclic voltammetry. The results indicate that the multilayer growth is linear for at least sixteen layers and the density of ferrocenes per layer is in the range of 6 Ă 10â11 mol cmâ2. Moreover, this method for LbL assembly is extended to surfaces which have been locally passivated by microcontact printing. By atomic force microscopy measurements it is possible to show that the covalent LbL deposition proceeds exclusively in the nonpassivated areas.
Covalently bound redox active layers are fabricated onto silicon (100) using decaallylferrocene in a layer-by-layer assembly with sequential photochemical thiol-ene reactions. The layer growth is linear for at least sixteen layers. The molar density of ferrocene for each layer is 6 Ă 10â11 mol cmâ2.
Twitching motility enables bacteria to move over surfaces using type IV pili as grappling hooks. Here it is shown that the motility of the round Neisseria gonorrhoeae as well as of rod-shaped Myxococcus xanthus is guided by elevations with dimension and depth corresponding to the size of the bacteria.
We report an active micromixer utilizing vortex generation due to non-equilibrium electrokinetics near micro/nanochannel interfaces.
Its design is relatively simple, consisting of a U-shaped microchannel and a set of nanochannels. We fabricated the micromixer
just using a two-step reactive ion etching process. We observed strong vortex generation in fluorescent microscopy experiments.
The mixing performance was evident in a combined pressure-driven and electroosmotic flows, compared with the case with a pure
pressure-driven flow. We characterized the micromixer for several conditions: different applied voltages, ion concentrations,
flow rates, and nanochannel widths. The experimental results show that the mixing performance is better with a higher applied
voltage, a lower ion concentration, and a wider nanochannel width. We quantified the mixing characteristics in terms of mixing
time. The lowest mixing time was 2 milliseconds with the voltage of 230 V and potassium chloride solutions of 0.1 mM. We expect
that the micromixer is beneficial in several applications requiring rapid mixing.
Content Type Journal Article
Category Research Paper
Pages 1-10
DOI 10.1007/s10404-011-0918-y
Authors
Seung Jun Lee, Department of Mechanical Engineering, Sogang University, Seoul, Republic of Korea
Daejoong Kim, Department of Mechanical Engineering, Sogang University, Seoul, Republic of Korea
Spatially overlapping plates in tiled configurations represent designs that are observed widely in nature (e.g., fish and snake scales) and man-made systems (e.g., shingled roofs) alike. This imbricate architecture offers fault-tolerant, multifunctional capabilities, in layouts that can provide mechanical flexibility even with full, 100% areal coverages of rigid plates. Here, the realization of such designs in microsystems technologies is presented, using a manufacturing approach that exploits strategies for deterministic materials assembly based on advanced forms of transfer printing. The architectures include heterogeneous combinations of silicon, photonic, and plasmonic scales, in imbricate layouts, anchored at their centers or edges to underlying substrates, ranging from elastomer sheets to silicon wafers. Analytical and computational mechanics modeling reveal distributions of stress and strain induced by deformation, and provide some useful design rules and scaling laws.
An imbricate architecturedesign for microsystems is presented. It offers fault-tolerant, multifunctional capabilities in layouts that can provide mechanical flexibility even with full, 100% areal coverage of rigid plates. Such designs are implemented in flexible heterogeneous photonic surfaces including combinations of silicon, photonic, and plasmonic scales using a manufacturing approach based on transfer printing.
Lab Chip, 2012, Advance Article DOI: 10.1039/C2LC21168H, Paper
Baoqing Nie, Siyuan Xing, James D. Brandt, Tingrui Pan We presented a novel droplet-based pressure sensing device, utilizing an elastic electrolyte-electrode contact with large interfacial capacitance, to achieve ultrahigh sensitivity (1.58 [small mu ]F kPa-1) and resolution (1.8 Pa) with flexible and transparent constructs. To cite this article before page numbers are assigned, use the DOI form of citation above. The content of this RSS Feed (c) The Royal Society of Chemistry
Creating and maintaining a precise molecular gradient which is stable in space and time are essential to studies of chemotaxis.
This paper describes a simple, compact, and user-friendly microfluidic device using a passive pumping method to drive liquid
flow to generate a stable concentration gradient. A fluidic circuit is designed to offset the effects of the pressure imbalance
between the two inlets. After loading approximately the same amount of culture media containing different concentrations of
a certain chemotactic agent into the two inlet reservoirs, a linear concentration gradient will be automatically and quickly
established at the downstream. Our device takes advantage of passive pumping and is compact enough to fit into a Petri dish,
which is an attractive feature to biologists. Furthermore, this microfluidic gradient generator offers a platform for a facile
way of long-term imaging and analysis using high-resolution microscopy.
Content Type Journal Article
Category Research Paper
Pages 1-9
DOI 10.1007/s10404-011-0908-0
Authors
Yandong Gao, Department of Mechanical Engineering, Vanderbilt University, Nashville, TN 37235, USA
Jiashu Sun, Department of Mechanical Engineering, Vanderbilt University, Nashville, TN 37235, USA
Wan-Hsin Lin, Department of Biological Sciences, Vanderbilt Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, TN 37235, USA
Donna J. Webb, Department of Biological Sciences, Vanderbilt Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, TN 37235, USA
Deyu Li, Department of Mechanical Engineering, Vanderbilt University, Nashville, TN 37235, USA
Sub-diffraction-limited imaging of fluorescent monomers on sliding microtubules in vitro by nanoscale localization sampling (NLS) is reported. NLS is based on periodic nanohole antenna arrays that create locally amplified electromagnetic hot spots through surface plasmon localization. The localized near-field hot spot temporally samples microtubular movement for enhanced spatial resolution. A fourfold improvement in spatial resolution compared to conventional wide-field microscopy is demonstrated. The resolution enhancement is achieved by imaging rhodamine-labeled microtubules that are sampled by the hot spots to provide sub-diffraction-limited images at 76 nm resolution in the direction of movement and 135 nm orthogonally. The intensity distribution produced by the NLS is measured to be broader than that of conventional imaging, which is consistent with the improvement of imaging resolution. Correlation studies between neighboring nanoantennas are also performed. This confirms the possibility of measuring microtubular transport dynamics. NLS can be useful for moving objects that have a high labeling density or for performing fluctuation spectroscopy in small volumes, and may allow âsuper-resolution on demandâ by customizing nanoantenna structures for specific resolution needs.
Sub-diffraction-limited imaging of fluorescent monomers on sliding microtubules in vitro is performed by nanoscale localization sampling (NLS). NLS is based on periodic nanohole antenna arrays that create local hot spots through surface plasmon localization. A fourfold improvement in spatial resolution is achieved by imaging rhodamine-labeled microtubules at 76 nm resolution in the direction of movement and 135 nm orthogonally.
This paper significantly extends previous studies to the transition regime by employing the second-order slip boundary conditions.
A simple analytical model with second-order slip boundary conditions for a normalized Poiseuille number is proposed. The model
can be applied to either rarefied gas flows or apparent liquid slip flows. The developed simple models can be used to predict
the Poiseuille number, mass flow rate, tangential momentum accommodation coefficient, pressure distribution of gaseous flow
in noncircular microchannels and nanochannels by the research community for the practical engineering design of microchannels
and nanochannels. The developed second-order models are preferable since the difficulty and âinvestmentâ is negligible compared
with the cost of alternative methods such as molecular simulations or solutions of Boltzmann equation. NavierâStokes equations
with second-order slip models can be used to predict quantities of engineering interest such as the Poiseuille number, tangential
momentum accommodation coefficient, mass flow rate, pressure distribution, and pressure drop beyond its typically acknowledged
limit of application. The appropriate or effective second-order slip coefficients include the contribution of the Knudsen
layers in order to capture the complete solution of the Boltzmann equation for the Poiseuille number, mass flow rate, and
pressure distribution. It could be reasonable that various researchers proposed different second-order slip coefficients because
the values are naturally different in different Knudsen number regimes. It is analytically shown that the Knudsenâs minimum
can be predicted with the second-order model and the Knudsen value of the occurrence of Knudsenâs minimum depends on inlet
and outlet pressure ratio. The compressibility and rarefaction effects on mass flow rate and the curvature of the pressure
distribution by employing first-order and second-order slip flow models are analyzed and compared. The condition of linear
pressure distribution is given.
Content Type Journal Article
Category Research Paper
Pages 1-16
DOI 10.1007/s10404-011-0924-0
Authors
Zhipeng Duan, University of Waterloo, Waterloo, N2L3G1 Canada
Under control: Controlled assemblies of gold nanorods in a poly(vinyl alcohol) (PVA) nanofiber matrix with tunable optical properties can be achieved by using electrospinning. The resultant assemblies can be used as substrates for surface-enhanced Raman spectroscopy (SERS). This work provides a facile way to control alignment of anisotropic nanostructures in a polymer nanofiber matrix and generates new assemblies with interesting properties.
A systematic study of the thermal transport properties of individual single-crystal zinc oxide (ZnO) nanowires (NWs) with diameters in the range of âź50â210 nm is presented. The thermal conductivity of the NWs is found to be dramatically reduced by at least an order of magnitude compared to bulk values, due to enhanced phonon-boundary scattering with a reduction in sample size. While the conventional phonon transport model can qualitatively explain the temperature dependence, it fails to account for the diameter dependence. An empirical relationship for assessing diameter-dependent thermal properties is observed, which shows an approximately linear dependence of the thermal conductivity on the cross-sectional area of the NWs in the measured diameter range. Furthermore, it is found that an amorphous-carbon layer coating on the NWs does not perturb the thermal properties of the NW cores, whereas 30 keV Ga+ ion irradiation at low dose (âź4 Ă 1014 cmâ2) leads to a remarkable reduction of the thermal conductivity of the ZnO NWs.
Thermal transport properties of individual zinc oxide nanowires are characterized using a suspended micro-electroâthermal device. It is found that the thermal conductivities of the nanowires are dramatically reduced by at least one order of magnitude compared to bulk values. An empirical relationship for assessing diameter-dependent thermal properties is observed, which shows an approximately linear dependence of the thermal conductivity on the cross-section area of the nanowires in the measured diameter range.
We present a deposited microbead plug (DMBP)-based microfluidic chip capable of performing plasma extraction and on-chip immunoassay.
The DMBP used as a porous blood filter provides pure blood plasma without the contamination of blood cells or beads. Capillary-driven
flow eliminates the requirement of external pumps. The human IgG and goat anti-human IgG sample-to-answer assay was performed
in this chip within 600 s using only a 10 Îźl whole-blood sample. This easy-to-use, rapid, inexpensive, and disposable DMBP-based
chip holds a great promise for point-of-care application.
Content Type Journal Article
Category Short Communication
Pages 1-6
DOI 10.1007/s10404-011-0911-5
Authors
Chunyu Li, Key Laboratory for Micro/Nano Technology and System of Liaoning Province, Dalian University of Technology, Dalian, China
Chong Liu, Key Laboratory for Micro/Nano Technology and System of Liaoning Province, Dalian University of Technology, Dalian, China
Zheng Xu, Key Laboratory for Micro/Nano Technology and System of Liaoning Province, Dalian University of Technology, Dalian, China
Jingmin Li, Key Laboratory for Micro/Nano Technology and System of Liaoning Province, Dalian University of Technology, Dalian, China
Details of hydrodynamic focusing in a 2D microfluidic channel-junction are investigated experimentally and theoretically,
especially the effect on the focusing width of volumetric flow ratio r between main and side channels, as well as angle θ between channels. A non-linear relationship is observed where the focus
width decreases rapidly with increasing r and levels off at higher values. For the dependence on θ, results from both experiments and modeling show that an increased
focusing effect is obtained as θ approaches 90°. Long-range focusing is explored along a 1 cm long channel and it is observed
that in the middle section of the channel, a smaller θ induces less divergence. This effect is of importance for microfluidic
systems utilizing hydrodynamic focusing in long, straight channels.
Content Type Journal Article
Category Research Paper
Pages 1-9
DOI 10.1007/s10404-011-0923-1
Authors
Casper Kunstmann-Olsen, Mads Clausen Institute, University of Southern Denmark, Alsion 2, 6400 Sønderborg, Denmark
James D. Hoyland, Mads Clausen Institute, University of Southern Denmark, Alsion 2, 6400 Sønderborg, Denmark
Horst-Gßnter Rubahn, Mads Clausen Institute, University of Southern Denmark, Alsion 2, 6400 Sønderborg, Denmark
A versatile solvent-free method for surface modification of various materials including both metals and polymers is described.
Strong irreversible bonds were formed when substrates modified by initiated chemical vapor deposition (iCVD) of poly(1,3,5-trivinyltrimethylcyclotrisiloxane)
or poly(V3D3) and exposed to an oxygen plasma were brought into contact with plasma-treated poly(dimethylsiloxane) (PDMS).
The strength of these bonds was quantified by burst pressure testing microfluidic channels in the PDMS. The burst pressures
of PDMS bonded to various coated substrates were in some cases comparable to that of PDMS bonded directly to PDMS. In addition,
porous PTFE membrane coated with poly(V3D3) was successfully bonded to a PDMS microfluidic device and withstood pressures
of over 300 mmHg. Bond strength was shown to correlate with surface roughness and quality of the bond between the coating
and substrate. This work paves a methodology to fabricate microfluidic devices that include a specifically tailored membrane.
Furthermore, the bonded devices exhibited hydrolytic stability; no dramatic change was observed even after immersion in water
at room temperature over a period of 10 days.
Content Type Journal Article
Category Communication Paper
Pages 1-5
DOI 10.1007/s10404-011-0913-3
Authors
Ramaswamy Sreenivasan, Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
Erik K. Bassett, Laboratory of Tissue Engineering and Organ Fabrication, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA
Thomas M. Cervantes, Laboratory of Tissue Engineering and Organ Fabrication, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA
David M. Hoganson, Laboratory of Tissue Engineering and Organ Fabrication, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA
Joseph P. Vacanti, Laboratory of Tissue Engineering and Organ Fabrication, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA
Karen K. Gleason, Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
We have developed an on-chip CO2 incubation system based on mass/heat transfer from aqueous solutions of bicarbonate source to cell culture media through
a permeable poly(dimethylsiloxane) (PDMS) wall. Heating a carbonate-buffered bicarbonate solution successfully regulated CO2 generation without any feedback control. Because a microfluidic cell culture chip with the incubation system does not require
an external chamber or gas supply, the entire microfluidic cell culture setup becomes pocket sized. Using 5 ml of 0.8 M sodium
bicarbonate with 65 mM sodium carbonate as the water jacket, the chip maintained the temperature, osmolality, and pH of 750 Îźl
cell culture medium within physiological levels when the chip was placed on a 37°C surface. The osmolality shift and pCO2 of the media reservoir stabilized within <5 mmol/kg and 5.0 ¹ 1.0% over at least 9 days. The incubation capabilities were
demonstrated through microfluidic culture of COS-7 epithelial cells under an inverted microscope for 17 days.
Content Type Journal Article
Category Research Paper
Pages 1-9
DOI 10.1007/s10404-011-0925-z
Authors
Atsushi Takano, School of Science and Engineering, Tokyo Denki University, Ishizaka, Hatoyama-machi, Hiki-gun, Saitama 350-0394, Japan
Masato Tanaka, School of Science and Engineering, Tokyo Denki University, Ishizaka, Hatoyama-machi, Hiki-gun, Saitama 350-0394, Japan
Nobuyuki Futai, Frontier R&D Center, Tokyo Denki University, Ishizaka, Hatoyama-machi, Hiki-gun, Saitama 350-0394, Japan
This paper presents the implementation of a multiple analyte enzyme assay, based on the sequential injection of the different
enzyme solutions, in an electrokinetic driven microfluidic chip. The assay methodology for the simultaneous quantification
of d-glucose and d-fructose was reported in previous publications but here the real integration of both enzyme assays was achieved. When assays
were executed separately, good reproducibility was observed with average CV values of 5.2% and 4.5% for the d-glucose and d-fructose assay, respectively. Next, the assays for the quantification of d-glucose and d-fructose were integrated simultaneously on chip, where each assay was executed consecutively in the same microreactor by
applying a specific sequence of potentials at the reservoirs. This article proves the integration of a sequential based quantification
approach in continuous microfluidic chips with electrokinetic actuation.
Content Type Journal Article
Category Research Paper
Pages 1-8
DOI 10.1007/s10404-011-0920-4
Authors
Yegermal Tesfaw Atalay, BIOSYST-MeBioS, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Willem de Croylaan 42, 3001 Leuven, Belgium
Steven Vermeir, BIOSYST-MeBioS, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Willem de Croylaan 42, 3001 Leuven, Belgium
Nicolas Vergauwe, BIOSYST-MeBioS, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Willem de Croylaan 42, 3001 Leuven, Belgium
Daan Witters, BIOSYST-MeBioS, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Willem de Croylaan 42, 3001 Leuven, Belgium
Pieter Verboven, BIOSYST-MeBioS, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Willem de Croylaan 42, 3001 Leuven, Belgium
Bart M. Nicolai, BIOSYST-MeBioS, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Willem de Croylaan 42, 3001 Leuven, Belgium
Jeroen Lammertyn, BIOSYST-MeBioS, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Willem de Croylaan 42, 3001 Leuven, Belgium
We report a novel micro magnetic gyromixer designed for accelerating mixing hence reactions in droplets. The gyromixer is
fabricated with magnetite-PDMS composite using soft lithography. The mixer spins and balances itself on the droplet surface
through the gyroscopic effect, rapidly homogenizing the enclosed reagents by stretching and folding internal fluid streamlines
to enhance mixing. We examined the capability of the gyromixer for improving biochemical reactions in droplets by monitoring
the biotinâstreptavidin binding as a linker in a quantum dot fluorescence resonant energy transfer sensing system. The remotely
controlled gyromixer exhibits high flexibility and potential for integration in a variety of droplet-based miniaturized total
analysis systems to reduce turnaround times.
Content Type Journal Article
Category Research Paper
Pages 1-8
DOI 10.1007/s10404-011-0922-2
Authors
Yi Zhang, Department of Biomedical Engineering, Johns Hopkins University, Clark 122, 3400 North Charles Street, Baltimore, MD 21218, USA
Tza-Huei Wang, Department of Mechanical Engineering, Sidney Kimmel Comprehensive Cancer Center, Center of Cancer Nanotechnology Excellence at Johns Hopkins, Johns Hopkins University, Latrobe 108, 3400 North Charles Street, Baltimore, MD 21218, USA
In in-vivo microsystems, one of the components is a biocompatible micropump in order to produce the necessary force to deliver
the fluid from the inlet to the outlet. In this contribution, a flexible micropump is fabricated which is aimed to be suitable
in drug delivery applications. It provides high degree of biocompatibility, since the only employed materials are implantation
grade polydimethylsiloxane elastomer and gold for the electrical interconnects. The working principle of the micropump is
based on transverse DC electroosmosis which is a new variant of conventionally applied high voltage DC electroosmosis. This
new technique is based on topography irregularities introduced in the channel resulting in a non-uniform charge distribution.
The advantage is to drive the micropump using a relatively low DC voltage of 10 V while getting an effective flow speed of
60 Îźm/s. In order to characterize the flow speed, dyed 3 Îźm beads are dispersed in the working fluid and their speed is measured
by the line scanning technique using a confocal microscope. It is also observed that the flow has a helical profile which
is an attractive feature for an efficient micro-mixer in active microfluidics and Îź-TAS applications.
Content Type Journal Article
Category Research Paper
Pages 1-7
DOI 10.1007/s10404-011-0905-3
Authors
Amir Jahanshahi, Department ELIS, Cmst, Ghent University, Technologiepark 914a, 9052 Ghent, Belgium
Fabrice Axisa, Microsys, University of Liege, Liege, Belgium
Jan Vanfleteren, Department IMEC, Cmst, Ghent University, Technologiepark 914a, 9052 Ghent, Belgium
A new droplet-driving scheme for digital microfluidics termed the âpre-charging of a dropletâ is demonstrated. In this method,
a droplet is initially charged by applying âpre-chargingâ voltage between the droplet and an electrode buried under dielectric
layers. The droplet is then driven to the next electrode by applying âdrivingâ voltage between two adjacent buried electrodes.
The concept of pre-charging was proved by the polarity of the charge stored in the droplet. When the droplet is pre-charged
with positive voltage, it is driven with negative voltage and vice versa. Therefore, the magnitudes of the pre-charging and
driving voltages are identical, but only with the opposite polarity. A 2.5-ÎźL deionized water droplet is pre-charged and driven
at a minimal voltage of 12 V. The charge stored in the droplet by this pre-charging method remained for more than 2 min, and
the driving actuation could be repeated more than 150 times while the droplet remained its charged state. This method suggests
a new means of driving a droplet for digital microfluidics at a relatively low voltage by utilizing both the electrostatic
and dielectrophoretic force in the droplet transport process with a simpler structure compared to other single-plate structured
devices.
Content Type Journal Article
Category Communication Paper
Pages 1-7
DOI 10.1007/s10404-011-0921-3
Authors
Kyungyong Choi, Department of Electrical Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, Republic of Korea
Maesoon Im, Department of Neurosurgery, Massachusetts General Hospital (MGH) and Harvard Medical School, 185 Cambridge Street, Boston, MA 02114, USA
Ji-Min Choi, Department of Electrical Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, Republic of Korea
Yang-Kyu Choi, Department of Electrical Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, Republic of Korea
We report a simple and cost-effective method for fabricating integrated electronic-microfluidic devices with multilayer configurations.
A CO2 laser plotter was employed to directly write patterns on a transferred polydimethylsiloxane (PDMS) layer, which served as
both a bonding and a working layer. The integration of electronics in microfluidic devices was achieved by an alignment bonding
of top and bottom electrode-patterned substrates fabricated with conventional lithography, sputtering and lift-off techniques.
Processes of the developed fabrication method were illustrated. Major issues associated with this method as PDMS surface treatment
and characterization, thickness-control of the transferred PDMS layer, and laser parameters optimization were discussed, along
with the examination and testing of bonding with two representative materials (glass and silicon). The capability of this
method was further demonstrated by fabricating a microfluidic chip with sputter-coated electrodes on the top and bottom substrates.
The device functioning as a microparticle focusing and trapping chip was experimentally verified. It is confirmed that the
proposed method has many advantages, including simple and fast fabrication process, low cost, easy integration of electronics,
strong bonding strength, chemical and biological compatibility, etc.
Content Type Journal Article
Category Research Paper
Pages 1-10
DOI 10.1007/s10404-011-0917-z
Authors
Ming Li, School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, 2522 NSW, Australia
Shunbo Li, Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
Jinbo Wu, Nano Science and Technology Program and KAUST-HKUST Micro/Nanofluidic Joint Laboratory, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
Weijia Wen, Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
Weihua Li, School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, 2522 NSW, Australia
Gursel Alici, School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, 2522 NSW, Australia
The study deals with a microfluidic method to investigate the transient behavior of microcapsules in flow. The technique consists
of investigating ovalbumin microcapsules passing through a convergentâdivergent microchannel made of PolyDiMethylSiloxane.
We work with three types of square microchannel with, respectively, cross section values of h Ă h = 30 Ă 30, 50 Ă 50 and 70 Ă 70 Îźm. The microchannels length is L = 3h. We analyze the kinetics of deformation of the microcapsules in the microchannels for velocity ranging from 2 to 5 cm/s and
for microcapsule size ratio d/h ranging from 0.9 to 2.5. The relaxation process at the pore outlet is modeled using an exponential relaxation law. We show
that that the relaxation time at the divergent outlet depends on the microcapsule size ratio d/h. Thanks to the analytical expression of the relaxation, we extract a shear modulus of the membrane equal to 0.04 N/m. This
value is consistent with the value of 0.07 N/m that we found using the steady state analysis performed in cylindrical glass
capillaries. Thus, it is interesting to notice that the microcapsule behavior based on a simple analytical model can be successfully
described despite the complex flow situation consisting of deformable microcapsule in confined square microchannels.
Content Type Journal Article
Category Research Paper
Pages 1-10
DOI 10.1007/s10404-011-0907-1
Authors
E. Leclerc, UMR CNRS 6600, BiomÊcanique et BioingÊnierie, UniversitÊ de Technologie de Compiègne, Compiègne, France
H. Kinoshita, Institute of Industrial Science, The University of Tokyo, Tokyo, Japan
T. Fujii, Institute of Industrial Science, The University of Tokyo, Tokyo, Japan
D. Barthès-Biesel, UMR CNRS 6600, BiomÊcanique et BioingÊnierie, UniversitÊ de Technologie de Compiègne, Compiègne, France
An ever increasing demand for packaging more energy on-board to meet the needs of power hungry microsystems is driving the
miniaturization of power generators. We report a fully integrated Power MEMS, in the 10-ÎźL size, designed to deliver high
energy and power densities. On-board hydrogen production and an efficient control scheme that facilitates integration with
a fuel cell membrane electrode assembly are key elements for micro energy conversion. A millimeter-scale reactor produces
hydrogen by hydrolysis of CaH2 and LiAlH4, to yield energy densities of the order of 200 Whr/L. A passive microfluidic control scheme, incorporating surface tension
to pump water in a microchannel for hydrolysis and microvalve control using hydrogen backpressure, facilitates delivery and
regulation and eliminates bulky auxiliaries that consume parasitic power. We tested the ability of this control scheme to
improve uniformity of power delivery during long periods of lower demand, with fast switching to mass transport regime on
the order of seconds, and realized peak power density of up to 391.85 W/L. Prototypes have been tested for duty periods from
2â48 h, with multiple switching of power demand in order to establish performance across multiple regimes. Critical to the
realization of the integrated power MEMS, and its energy and power density, are effects of water transport and byproduct hydrate
swelling on hydrogen production in the microreactor. While CaH2 showed superior hydrogen release kinetics that enhances power density, LiAlH4 provided greater energy density due to reduced byproduct expansion that permitted increased hydrogen production.
Content Type Journal Article
Category Research Paper
Pages 1-15
DOI 10.1007/s10404-011-0916-0
Authors
Vikhram V. Swaminathan, Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
Likun Zhu, Department of Mechanical Engineering, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA
Bogdan Gurau, Gas Technology Institute, Basic Energy and Environment, Des Plaines, IL 60018, USA
Richard I. Masel, Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
Mark A. Shannon, Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
Insulator-based dielectrophoresis (iDEP) has been successfully used for on-chip manipulations of biological samples. Despite
its effectiveness, iDEP typically requires high DC voltages to achieve sufficient electric field; this is mainly due to the
coupled phenomena among linear electrokinetics: electroosmosis (EO) and electrophoresis (EP) and nonlinear electrokinetics:
dielectrophoresis (DEP). This paper presents a microfluidic technique using DC-offset AC electric field for electrokinetic
concentration of particles and cells by repulsive iDEP. This technique introduces AC electric field for producing iDEP which
is decoupled from electroosmosis (EO) and electrophoresis (EP). The repulsive iDEP is generated in a PDMS tapered contraction
channel that induces non-uniform electric field. The benefits of introducing AC electric field component are threefold: (i)
it contributes to DEP force acting on particles, (ii) it suppresses EO flow and (iii) it does not cause any EP motion. As
a result, the required DC field component that is mainly used to transport particles on the basis of EO and EP can be significantly
reduced. Experimental results supported by numerical simulations showed that the total DC-offset AC electric field strength
required to concentrate 15-Îźm particles is significantly reduced up to 85.9% as compared to using sole DC electric field.
Parametric experimental studies showed that the higher buffer concentration, larger particle size and higher ratio of AC-to-DC
electric field are favorable for particle concentration. In addition, the proposed technique was demonstrated for concentration
of yeast cells.
Content Type Journal Article
Category Research Paper
Pages 1-11
DOI 10.1007/s10404-011-0919-x
Authors
Nuttawut Lewpiriyawong, School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore, 639798 Singapore
Chun Yang, School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore, 639798 Singapore
Yee Cheong Lam, School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore, 639798 Singapore
This study presents the microbubble coalescence process in a confined microchannel. Triple T-junction microfluidic devices
with different main channel size were designed to generate monodispersed microbubble pairs with air/n-butyl alcoholâglycerol solution as the working system. The head-on collision of microbubble pair was realized in the microfluidic
devices. Three collision results including absolute coalescence, probabilistic coalescence, and non-coalescence were distinguished.
The effects of liquid viscosities and two-phase superficial velocities on the coalescence behavior were determined. The results
showed that microbubble coalescence process in the confined space was slightly faster than in the free space. Increasing liquid
viscosity apparently prevents coalescence. In the probabilistic coalescence region, higher two-phase superficial velocity
could reduce the percentage of coalescence events. Two characteristic parameters representing the bubble contact time and
film drainage time have been introduced to analyze the microbubble coalescence behaviors and a linear correlation could clearly
distinguish the coalescence and non-coalescence region.
Content Type Journal Article
Category Research Paper
Pages 1-8
DOI 10.1007/s10404-011-0912-4
Authors
Lu Yang, The State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing, 100084 China
Kai Wang, The State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing, 100084 China
Jing Tan, The State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing, 100084 China
Yangcheng Lu, The State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing, 100084 China
Guangsheng Luo, The State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing, 100084 China
Here we present the liquidâliquid microflows and dispersion rules in micro-sieve devices with two different sized pores. The
flow pattern, flux distribution and droplet size were investigated to discuss the effect of pore size deviation. Three flow
patterns including dripping flow from a single active pore, drippingâdripping flow and drippingâjetting flow from two active
pores were identified. A modified active pore model based on a pressure drop balance has been established. The model can predict
the transition from a single active pore flow regime to a two active pore flow regime very well. In the latter regime, interactions
between the small and large pores can result in drippingâdripping flow at low trans-pore flux and drippingâjetting flow at
high trans-pore flux. Controlling the flow pattern in drippingâdripping flow is favorable to decreasing droplet polydispersity.
Content Type Journal Article
Category Research Paper
Pages 1-10
DOI 10.1007/s10404-011-0914-2
Authors
H. W. Shao, The State Key Lab of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing, 100084 China
Y. C. Lu, The State Key Lab of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing, 100084 China
K. Wang, The State Key Lab of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing, 100084 China
G. S. Luo, The State Key Lab of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing, 100084 China
Two simple optofluidic devices based on a microprism and a refraction channel, respectively, are proposed for measuring the
refractive index of fluids. The microprism chip consists of an optical waveguide channel and a single triangular chamber filled
with the test fluid, while the refraction channel chip consists of a single turning channel which functions as a liquid-core/solid-cladding
optical waveguide. In both chips, the refractive index of the test fluid is calculated from a CCD image of the refracted ray
in accordance with simple geometrical optics principles. The experimental results show that the refraction channel chip provides
a more accurate measurement performance than the microprism chip; particularly for colloidal samples. However, the refraction
channel chip is suitable only for the measurement of fluids with a refractive index greater than that of the chip substrate.
Overall, the results presented in this study show that both devices provide a simple, low cost and effective means of determining
the refractive index of a wide range of common test fluids with nano-liter volume.
Content Type Journal Article
Category Research Paper
Pages 1-8
DOI 10.1007/s10404-011-0915-1
Authors
Kuo-Sheng Chao, Department of Engineering Science, National Cheng Kung University, Tainan, Taiwan
Tsung-Yu Lin, Department of Engineering Science, National Cheng Kung University, Tainan, Taiwan
Ruey-Jen Yang, Department of Engineering Science, National Cheng Kung University, Tainan, Taiwan
A âgold rushâ has been triggered all over the world for exploiting the possible applications of graphene-based nanomaterials. For this purpose, two important problems have to be solved; one is the preparation of graphene-based nanomaterials with well-defined structures, and the other is the controllable fabrication of these materials into functional devices. This review gives a brief overview of the recent research concerning chemical and thermal approaches toward the production of well-defined graphene-based nanomaterials and their applications in energy-related areas, including solar cells, lithium ion secondary batteries, supercapacitors, and catalysis.
With a focus on chemical and thermal approaches toward the production of well-defined graphene-based nanomaterials, this paper gives a brief overview of the recent exciting research results and the potential applications of graphene nanomaterials in energy-related areasâincluding solar cells, lithium ion secondary batteries, supercapacitors, and catalysisâwhich have attracted great attention all over the world.
Bicelles emerge as promising membrane models, and because of their attractive combination of lipid composition, small size and morphological versatility, they become new targets in skin research. Bicelles are able to modify skin biophysical parameters and modulate the skin's barrier function, acting to enhance drug penetration. Because of their nanostructured assemblies, bicelles have the ability to penetrate through the narrow intercellular spaces of the stratum corneum of the skin to reinforce its lipid lamellae. The bicelle structure also allows for the incorporation of different molecules that can be carried through the skin layers. All of these characteristics can be modulated by varying the lipid composition and experimental conditions. The remarkable versatility of bicelles is their most important characteristic, which makes their use possible in various fields. This system represents a platform for dermal applications. In this review, an overview of the main properties of bicelles and their effects on the skin are presented.
Bicelles have the ability to penetrate through the narrow intercellular spaces of the stratum corneum of the skin to reinforce its lipid lamellae. Their structure also allows for the incorporation of different molecules that can be carried through the skin layers.
We experimentally examine the dynamics of droplet assembly and recombination processes in a two-dimensional pore-model system.
Monodisperse trains of droplets are formed by focusing streams of immiscible fluids into a square microchannel that is connected
to a diverging/converging slit microfluidic chamber. We focus on the limit of dilute emulsions and investigate the formation
and stability of crystal-like structures when droplets are hydrodynamically coupled in the chamber. The minimal distance between
droplets and the spread of droplet lattices are measured as a function of initial control parameters and the relationship
between droplet velocity and trajectory is discussed. We demonstrate that the onset of coalescence depends on both the capillary
number based on the viscosity of the external phase and the droplet concentration. The draining time of the thin film between
droplets in apparent contact is found to depend on fluid characteristics. Such property allows us to examine the crossover
between non-coalescing and coalescing droplet microflows by varying the residence time of the dispersion in the microfluidic
chamber. This work characterizes droplet interaction and coalescence phenomena during multiphase transport in a simple extensional
microgeometry.
Content Type Journal Article
Category Research Paper
Pages 1-10
DOI 10.1007/s10404-011-0909-z
Authors
Bibin M. Jose, Mechanical Engineering Department, Stony Brook University, Stony Brook, NY 11794, USA
Thomas Cubaud, Mechanical Engineering Department, Stony Brook University, Stony Brook, NY 11794, USA
In this work, we present the synthesis and characterization of a new surfactant molecule obtained from a byproduct of the
cashew nut processing (diphosphorylated cardol, DPC). It is herein used to overcoat magnetic nanoparticles showing spinel
structures in order to create new ferrofluids. The nanoparticle structure and magnetic properties have been deeply investigated.
DPC-functionalized Fe3O4 and NiFe2O4 samples exhibit higher magnetic saturation than DPCâCoFe2O4. These new ferrofluids reveal appealing as possible nanoparticle stabilizing molecules, magnetic resonance imaging agents,
storage systems or in any material science field that requires the employment of biocompatible magnetic stable fluids.
Content Type Journal Article
Category Research Paper
Pages 1-10
DOI 10.1007/s10404-011-0910-6
Authors
A. C. H. Barreto, Grupo de QuĂmica de Materiais Avançados (GQMAT), Departamento de QuĂmica AnalĂtica e FĂsico-QuĂmica, Universidade Federal do CearĂĄ, UFC, Campus do Pici, CP 12100, Fortaleza, CE CEP 60451-970, Brazil
F. J. N. Maia, LaboratĂłrio de Produtos e Tecnologia em Processos, LPT, Universidade Federal do CearĂĄ, Campus do Pici, Fortaleza, CE 60455-900, Brazil
V. R. Santiago, Grupo de QuĂmica de Materiais Avançados (GQMAT), Departamento de QuĂmica AnalĂtica e FĂsico-QuĂmica, Universidade Federal do CearĂĄ, UFC, Campus do Pici, CP 12100, Fortaleza, CE CEP 60451-970, Brazil
V. G. P. Ribeiro, LaboratĂłrio de Produtos e Tecnologia em Processos, LPT, Universidade Federal do CearĂĄ, Campus do Pici, Fortaleza, CE 60455-900, Brazil
J. C. Denardin, Departamento de FĂsica, Universidad de Santiago de Chile, USACH, Av. Ecuador, 3493 Santiago, Chile
Giuseppe Mele, Dipartimento di Ingegneria dellâInnovazione, UniversitĂ del Salento, Via Arnesano, 73100 Lecce, Italy
L. Carbone, Istituto Nanoscienze UOS Lecce, NNL, Via Arnesano 16, 73100 Lecce, Italy
Diego Lomonaco, LaboratĂłrio de Produtos e Tecnologia em Processos, LPT, Universidade Federal do CearĂĄ, Campus do Pici, Fortaleza, CE 60455-900, Brazil
S. E. Mazzetto, LaboratĂłrio de Produtos e Tecnologia em Processos, LPT, Universidade Federal do CearĂĄ, Campus do Pici, Fortaleza, CE 60455-900, Brazil
P. B. A. Fechine, Grupo de QuĂmica de Materiais Avançados (GQMAT), Departamento de QuĂmica AnalĂtica e FĂsico-QuĂmica, Universidade Federal do CearĂĄ, UFC, Campus do Pici, CP 12100, Fortaleza, CE CEP 60451-970, Brazil
By careful management of the adsorption preference of organic molecules at faceted vicinal surfaces, organic alternating structures can be extended to multilayers and multicomponent with tunable size scales ranging from several to a few tens nanometers.
