Labor Miniaturisierung - Neueste Forschungsartikel der Fachverlage
Aktuelle Artikel zur Miniaturisierung von analytischen Labortests, Lab-on-a-Chip und Laborgeraeten - sortiert nach Erscheinungsdatum.
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beruecksichtige naturwissenschaftliche Journale:
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:
The formation of nanorods, driven by the physicochemical phenomena during the freezing and after the aging of frozen ceria nanoparticle suspensions, is reported. During freezing of a dilute aqueous solution of CeO2 nanocrystals, some nuclei remain in solution while others are trapped inside micro- and nanometer voids formed within the growing ice front. Over time (2-3 weeks) the particles trapped within the nanometer-wide voids in the ice combine by an oriented attachment process to form ceria nanorods. The experimental observations are consistent with molecular dynamics simulations of particle aggregation in constrained environments. These observations suggest a possible strategy for the templated formation of nanostructures through self-assembly by exploiting natural phenomena, such as voids formed during freezing of water. This research suggests a very simple, green chemical route to guide the formation of one- and three-dimensional self-assembled nanostructures.
A novel bioassay strategy is designed to detect small-molecule targets such as cocaine, potassium, and adenosine, based on gold nanoparticles (AuNPs) and engineered DNA aptamers. In this design, an aptamer is engineered to be two pieces of random, coil-like single-stranded DNA, which reassembles into the intact aptamer tertiary structure in the presence of the specific target. AuNPs can effectively differentiate between these two states via their characteristic surface-plasmon resonance-based color change. Using this method, cocaine in the low-micromolar range is selectively detected within minutes. This strategy is also shown to be generic and applicable to the detection of several other small-molecule targets.
Enhancements in both the rate and extent of grafting of poly(9,9[prime]-n-dihexyl fluorene) (PDHF) onto flat and nanopatterned crosslinked photopolymer films are described. Reactivity of the surfaces toward grafting via the Yamamoto-type Ni(0)-mediated coupling reaction is increased by synthesizing and incorporating 2,7-dibromo-9-fluorenyl methacrylate (DBFM, 2) as a new grafting agent. Varying the concentration of surface-embedded DBFM is shown to control both overall graft formation and fluorescence with a maximum thickness of up to 30 nm and peak emission at 407 nm for 40 wt% loading. In addition, microwave irradiation is introduced as an effective means to drive graft formation and thus allows fabrication of PDHF-functionalized surfaces in as little as 30 min. Both forms of improvement are extended to DBFM-embedded, nanocontact-molded features ranging in size from 100 µm to 100 nm in width and 60 nm in height. Microwave-assisted grafting from these patterned surfaces produces fluorescent features as imaged by optical microscopy and a corresponding increase in feature height as measured by atomic force microscopy.
R. Truckenmuller, S. Giselbrecht, C. van Blitterswijk, N. Dambrowsky, E. Gottwald, T. Mappes, A. Rolletschek, V. Saile, C. Trautmann, K.-F. Weibezahn, A. Welle
(Paper from Lab Chip)
R. Truckenmuller, Lab Chip, 2008, DOI: 10.1039/b803619e
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The content of this RSS Feed (c) The Royal Society of Chemistry
Chang-Hyung Choi, Jae-Hoon Jung, Dong-Wan Kim, Young-Min Chung, Chang-Soo Lee
(Paper from Lab Chip)
Chang-Hyung Choi, Lab Chip, 2008, DOI: 10.1039/b804839h
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The content of this RSS Feed (c) The Royal Society of Chemistry
Abstract The detachment of a single rigid sphere in a cylindrical PDMS microchannel has been investigated for systems where the particle
occupies greater than 50% of the channel cross-sectional area. The fluid velocity required to detach a particle adhering to
a microchannel wall is a function of many variables; however, only the effect of particle size is considered in this paper.
Experiments were performed for Reynolds numbers less than 0.1, and the ratio of particle diameter, dp, to channel dimension, D, was varied from 0.50 to 0.95 in a 230 ÎĽm channel. A nonionic surfactant (Tween 80) was used to minimize the effect of adhesive
forces other than van der Waals forces. In addition, a simple force-balance model based on particle lift, buoyancy, drag,
gravitational forces, and adhesion due to van der Waals forces has been developed to predict the velocity required for particle
detachment. The predicted and experimentally measured velocities agree relatively well within the limit of experimental error.
The detachment velocity was qualitatively found to increase with decreasing dp/D.
Content Type Journal Article
Category Research Paper
DOI 10.1007/s10404-008-0330-4
Authors
Nimisha Shukla, Missouri University of Science and Technology Department of Chemical and Biological Engineering Rolla MO 65409 USA
Kimberly H. Henthorn, Missouri University of Science and Technology Department of Chemical and Biological Engineering Rolla MO 65409 USA
A second-generation polyphenylene dendrimer 1 is shown to self-assemble into nanofibers. To guide the formation of the dendrimer fibers into well-defined patterns, 1H,1H,2H,2H-perfluorodecyltrichlorosilane is grafted in the gas phase onto a silicon substrate. De-wetting of the solution on the nanopatterned surface results in the formation of a nanostructured template, into which fiber growth subsequently occurs under the constraints set by the de-wetted morphology.
Edgar Gutierrez, Brian G. Petrich, Sanford J. Shattil, Mark H. Ginsberg, Alex Groisman, Ana Kasirer-Friede
(Paper from Lab Chip)
Edgar Gutierrez, Lab Chip, 2008, DOI: 10.1039/b804795b
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The content of this RSS Feed (c) The Royal Society of Chemistry
Kang Sun, Zongxing Wang, Xingyu Jiang
(Paper from Lab Chip)
Kang Sun, Lab Chip, 2008, DOI: 10.1039/b806140h
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The content of this RSS Feed (c) The Royal Society of Chemistry
Keith J. Morton, Kevin Loutherback, David W. Inglis, Ophelia K. Tsui, James C. Sturm, Stephen Y. Chou, Robert H. Austin
(Paper from Lab Chip)
Keith J. Morton, Lab Chip, 2008, DOI: 10.1039/b805614e
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The content of this RSS Feed (c) The Royal Society of Chemistry
Abstract This paper presents a detection scheme for analyzing the temperature distribution nearby the channel wall in a microfluidic
chip utilizing a temperature-dependent fluorescence dye. An advanced optical microscope system—total internal reflection fluorescence
microscope (TIRFM) is used for measuring the temperature distribution on the channel wall at the point of electroosmotic flow
in an electrokinetically driven microfluidic chip. In order to meet the short working distance of the objective type TIRFM
scheme, microscope cover glass slits are used to fabricate the microfluidic chips. The short fluorescence excitation depth
from a TIRFM system makes the intensity information obtained using TIRFM is not sensitive to the channel depth variation which
ususally biases the measured results while using a conventional Epi-fluorescence microscope (EPI-FM). Therefore, a TIRFM can
precisely describe the temperature profile of the distance within 100 nm of the channel wall where consists of the Stern layer
and the diffusion layer for an electrokinetic microfluidic system. Results indicate the proposed TIRFM provides higher measurement
sensitivity over the EPI-FM. Significant temperature gradient along the channel depth is experimentally observed. In addition,
the measured wall temperature distributions can be the boundary conditions for numerical investigation into the joule heating
effect. The proposed method gives a precise temperature profile of microfluidic channels and shows the substantial impact
on developing a numerical simulation model for precisely predicting the joule heating effect in microfluidic chips.
Content Type Journal Article
Category Research Paper
DOI 10.1007/s10404-008-0328-y
Authors
Lung-Ming Fu, National Pingtung University of Science and Technology Department of Materials Engineering Pingtung 912 Taiwan
Jing-Hui Wang, National Sun Yat-sen University Department of Mechanical and Electro-Mechanical Engineering Kaohsiung 804 Taiwan
Wen-Bo Luo, University of Science and Technology Beijing College of Mechanical Engineering 10003 Beijing China
Che-Hsin Lin, National Sun Yat-sen University Department of Mechanical and Electro-Mechanical Engineering Kaohsiung 804 Taiwan
Abstract In the present investigation, we have derived an efficient reduced-order model of the low-voltage cascade electroosmotic micropump.
This model can be combined with the equivalent circuit model of straight microchannels to construct a complete model for a
microfluidic device, which can be employed to implement modern control schemes. To demonstrate the efficiency of the reduced-order
model we employ it to estimate the zeta potentials of many subchannels in the micropump cascade using velocity measurements,
which is a preliminary step to the implementation of modern control schemes. It is found that a conjugate gradient procedure
employing the reduced-order model estimates accurately the zeta potential variation in the subchannels, which may be caused
by adhesion of biomolecules, even with noisy velocity measurements.
Content Type Journal Article
Category Research Paper
DOI 10.1007/s10404-008-0326-0
Authors
H. M. Park, Sogang University Department of Chemical and Biomolecular Engineering Shinsoo-Dong, Mapo-Gu Seoul South Korea
J. Y. Lim, Sogang University Department of Chemical and Biomolecular Engineering Shinsoo-Dong, Mapo-Gu Seoul South Korea
M. Behnam, G. V. Kaigala, M. Khorasani, P. Marshall, C. J. Backhouse, D. G. Elliott
(Paper from Lab Chip)
M. Behnam, Lab Chip, 2008, DOI: 10.1039/b804275f
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The content of this RSS Feed (c) The Royal Society of Chemistry
The present study demonstrates an unprecedented green process for the production of gold nanoparticles by simple treatment of gold salts with soybean extracts. Reduction capabilities of antioxidant phytochemicals present in soybean and their ability to reduce gold salts chemically to nanoparticles with subsequent coating of proteins and a host of other phytochemicals present in soybean on the freshly generated gold nanoparticles are discussed. The new genre of green nanoparticles exhibit remarkable in vitro stability in various buffers including saline, histidine, HSA, and cysteine solutions. MTT assays reveal that the green gold nanoparticles are nontoxic and thus provide excellent opportunities for their applications in nanomedicine for molecular imaging and therapy. The overall strategy described herein for the generation of gold nanoparticles meets all 12 principles of green chemistry, as no "man-made" chemicals, other than the gold salts, are used in the green nanotechnological process.
Vernella Vickerman, Jennifer Blundo, Seok Chung, Roger Kamm
(Paper from Lab Chip)
Vernella Vickerman, Lab Chip, 2008, DOI: 10.1039/b802395f
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The content of this RSS Feed (c) The Royal Society of Chemistry
Hui Yu, Yu Lu, Yi-ge Zhou, Feng-bin Wang, Feng-yun He, Xing-hua Xia
(Paper from Lab Chip)
Hui Yu, Lab Chip, 2008, DOI: 10.1039/b802778a
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The content of this RSS Feed (c) The Royal Society of Chemistry
Jong-Min Lim, Se-Heon Kim, Jae-Hoon Choi, Seung-Man Yang
(Paper from Lab Chip)
Jong-Min Lim, Lab Chip, 2008, DOI: 10.1039/b805341c
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The content of this RSS Feed (c) The Royal Society of Chemistry
Abstract A non-isothermal rarefied gas flow trough a long tube with an elliptical cross section due to pressure and temperature gradients
is studied on the basis of the S-model kinetic equation in the whole range of the Knudsen number covering both free molecular
regime and hydrodynamic one. A wide range of the pipe section aspect ratio is considered. The mass flow rate is calculated
as a function of the pressures and temperatures on the tube ends. The thermomolecular pressure effect has been modeled and
the coefficient of the thermomolecular pressure difference has been calculated in whole range of the Knudsen number and in
wide range of the pipe section aspect ratio.
Jungkyu Kim, Bruce K. Gale
(Paper from Lab Chip)
Jungkyu Kim, Lab Chip, 2008, DOI: 10.1039/b804624g
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The content of this RSS Feed (c) The Royal Society of Chemistry
Abstract A small-scale, trapezoidal rigid body in the gas-filled gap between two parallel plates at different temperatures is considered.
An analytical expression for the thermally induced force onto the body in the direction parallel to the plates valid for an
infinite Knudsen number is derived. For this purpose, diffuse reflection of the gas molecules at the solid walls is assumed.
Simultaneously, Monte Carlo simulations are performed allowing an extension of the analysis to Knudsen numbers of the order
of one. The numerical and the analytical results show excellent agreement, indicating that a temperature gradient orthogonal
to the plates can induce a significant force in parallel direction, a phenomenon without analogy in the macroworld. This force
is only slightly reduced when a Knudsen number of one is considered. In addition to the diffuse-reflection boundary condition,
a mixture of diffuse and specular reflection is studied. The practical relevance of the results is exemplified by considering
two scenarios with bodies of a specific geometry, among others a nanoscopic platelet.
Vinay V. Abhyankar, Michael W. Toepke, Christa L. Cortesio, Mary A. Lokuta, Anna Huttenlocher, David J. Beebe
(Paper from Lab Chip)
Vinay V. Abhyankar, Lab Chip, 2008, DOI: 10.1039/b803533d
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The content of this RSS Feed (c) The Royal Society of Chemistry
Tae-Ho Yoon, Sang-Hee Park, Kyoung-Ik Min, Xunli Zhang, Stephen J. Haswell, Dong-Pyo Kim
(Paper from Lab Chip)
Tae-Ho Yoon, Lab Chip, 2008, DOI: 10.1039/b804726j
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The content of this RSS Feed (c) The Royal Society of Chemistry
A simplified synthesis of hollow gold nanoshells 20-50 nm in diameter via the well-established templated galvanic replacement reaction of silver for gold is presented. The surface plasmon resonance absorbance of the nanoshells is tuned using basic colloid chemistry to control the size of the silver templates. The gold nanoshells have an aqueous core and are varied in size and shell thickness depending on the silver/gold reagent ratios. The template replacement chemistry is rapid, highly scalable, uses minimal amounts of toxic reagents, and in many cases is a true one-pot synthesis. The smallest nanoshells (20-nm diameter, 7-nm wall thickness) reach the highest temperature on irradiation with femtosecond light pulses in the near infrared and anneal to form spherical nanoparticles fastest, even though their plasmon resonance does not overlap as well as the larger nanoshells (50-nm diameter, 7-nm wall thickness) with 800-nm wavelength excitation.
Nanotubes are fabricated by atomic layer deposition (ALD) into nanopore arrays created by anodic aluminum oxide (AAO). A transmission electron microscopy (TEM) methodology is developed and applied to quantify the ALD conformality in the nanopores (thickness as a function of depth), and the results are compared to existing models for ALD conformality. ALD HfO2 nanotubes formed in AAO templates are released by dissolution of the Al2O3, transferred to a grid, and imaged by TEM. An algorithm is devised to automate the quantification of nanotube wall thickness as a function of position along the central axis of the nanotube, by using a cylindrical model for the nanotube. Diffusion-limited depletion occurs in the lower portion of the nanotubes and is characterized by a linear slope of decreasing thickness. Experimentally recorded slopes match well with two simple models of ALD within nanopores presented in the literature. The TEM analysis technique provides a method for the rapid analysis of such nanostructures in general, and is also a means to efficiently quantify ALD profiles in nanostructures for a variety of nanodevice applications.
The evolution of ionicity with size in highly ionic nanoparticles is investigated in small sesquioxide clusters. Representative clusters (Y2O3)N (N < 50) are theoretically analyzed by first-principle calculations within the density functional theory within the local-density approximation (DFT-LDA) framework and compared to experimental results obtained in an ultrahigh vacuum environment. By studying the structural relaxation and the electronic density of states as a function of size, the respective roles of ionicity and covalency are elucidated. For compounds as ionic as rare earth sesquioxides, the highly ionic bond essentially governs and preserves the crystalline structure. Particular attention is paid to the mechanism responsible for the surface relaxation. The role of the ions at the corners and edges appears prominent, especially in reducing the dipole carried by the particles. Eventually, contrary to the observations and computations concerning ionic surfaces, the mean ionicity remains constant as the size is reduced. It emphasizes that the description of highly ionic nanoparticles cannot be directly inferred from knowledge regarding the ionic surface reconstruction.
Abstract This communication describes novel 3-D manipulations of objects using an acoustically excited oscillating bubble deposited
on a hydrophobic rod tip. The oscillating bubble captures various millimeter- and micron-sized neighboring objects including
glass and polystyrene beads (~100 ÎĽm), fish egg, and live water flea (~1 mm). The captured objects are carried in a 3-D space
by traversing the bubble tip, and released at desired positions by simply turning off the oscillation. Carrying performance
is characterized along with high-speed imaging of oscillating bubbles by varying the frequency and amplitude of the acoustic
excitation and the carrying speed. The higher the oscillation amplitude, the higher the carrying efficiency. The maximum carrying
speed is measured at over 3 mm/s. This method is effective with a low-level acoustic excitation (bubble oscillation amplitude
relative to the diameter ≤5%), possibly providing a cost-effective, soft-contact manipulating tool for handling biological
objects.
Content Type Journal Article
Category Short Communication
DOI 10.1007/s10404-008-0324-2
Authors
Sang Kug Chung, University of Pittsburgh Department of Mechanical Engineering and Materials Science Pittsburgh USA
Sung Kwon Cho, University of Pittsburgh Department of Mechanical Engineering and Materials Science Pittsburgh USA
Abstract We present a microfluidic device for specific extraction and thermally activated release of analytes using nucleic acid aptamers.
The device primarily consists of a microchamber that is packed with aptamer-functionalized microbeads as a stationary phase,
and integrated with a micro heater and temperature sensor. We demonstrate the device operation by performing the extraction
of a metabolic analyte, adenosine monophosphate coupled with thiazole orange (TO-AMP), with high selectivity to an RNA aptamer.
Controlled release of TO-AMP from the aptamer surface is then conducted at low temperatures using on-chip thermal activation.
This allows isocratic analyte elution, which eliminates the use of potentially harsh reagents, and enables efficient regeneration
of the aptamer surfaces when device reusability is desired.
Content Type Journal Article
Category Research Paper
DOI 10.1007/s10404-008-0322-4
Authors
ThaiHuu Nguyen, Columbia University Department of Mechanical Engineering New York NY 10027 USA
Renjun Pei, Columbia University Department of Medicine New York NY 10032 USA
Milan Stojanovic, Columbia University Department of Medicine New York NY 10032 USA
Qiao Lin, Columbia University Department of Mechanical Engineering New York NY 10027 USA
Saurabh Vyawahare, Suresh Sitaula, Sujitha Martin, Dvin Adalian, Axel Scherer
(Paper from Lab Chip)
Saurabh Vyawahare, Lab Chip, 2008, DOI: 10.1039/b804515a
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The content of this RSS Feed (c) The Royal Society of Chemistry
Weiwei Shi, Jianhua Qin, Nannan Ye, Bingcheng Lin
(Communication from Lab Chip)
Weiwei Shi, Lab Chip, 2008, DOI: 10.1039/b808753a
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The content of this RSS Feed (c) The Royal Society of Chemistry
James Q. Boedicker, Liang Li, Timothy R. Kline, Rustem F. Ismagilov
(Paper from Lab Chip)
James Q. Boedicker, Lab Chip, 2008, 8, 1265 DOI: 10.1039/b804911d
The content of this RSS Feed (c) The Royal Society of Chemistry
Minsoung Rhee, Mark A. Burns
(Paper from Lab Chip)
Minsoung Rhee, Lab Chip, 2008, 8, 1365 DOI: 10.1039/b805137b
The content of this RSS Feed (c) The Royal Society of Chemistry
Po Ki Yuen
(Technical Note from Lab Chip)
Po Ki Yuen, Lab Chip, 2008, 8, 1374 DOI: 10.1039/b805086d
The content of this RSS Feed (c) The Royal Society of Chemistry
Abstract This paper reports experimental investigations on the droplet formation and size manipulation of deionized water (DIW) and
nanofluids in a microfluidic T-junction at different temperatures. Investigations of the effect of microchannel depths on
the droplet formation process showed that the smaller the depth of the channel the larger the increase of droplet size with
temperature. Sample nanofluids were prepared by dispersing 0.1 volume percentage of titanium dioxide (TiO2) nanoparticles of 15 nm and 10 nm Ă— 40 nm in DIW for their droplet formation experiments. The heater temperature also affects
the droplet formation process. Present results demonstrate that nanofluids exhibit different characteristics in droplet formation
with the temperature. Addition of spherical-shaped TiO2 (15 nm) nanoparticles in DIW results in much smaller droplet size compared to the cylindrical-shaped TiO2 (10 nm Ă— 40 nm) nanoparticles. Besides changing the interfacial properties of based fluid, nanoparticles can influence the
droplet formation of nanofluids by introducing interfacial slip at the interface. Other than nanofluid with cylindrical-shaped
nanoparticles, the droplet size was found to increase with increasing temperature.
Content Type Journal Article
Category Research Paper
DOI 10.1007/s10404-008-0323-3
Authors
S. M. Sohel Murshed, Nanyang Technological University School of Mechanical and Aerospace Engineering 50 Nanyang Avenue Singapore 639798 Singapore
Say Hwa Tan, Nanyang Technological University School of Mechanical and Aerospace Engineering 50 Nanyang Avenue Singapore 639798 Singapore
Nam Trung Nguyen, Nanyang Technological University School of Mechanical and Aerospace Engineering 50 Nanyang Avenue Singapore 639798 Singapore
Teck Neng Wong, Nanyang Technological University School of Mechanical and Aerospace Engineering 50 Nanyang Avenue Singapore 639798 Singapore
Levent Yobas, Institute of Microelectronics Science Park II Singapore 117685l Singapore
Andrea Adamo, Klavs F. Jensen
(Communication from Lab Chip)
Andrea Adamo, Lab Chip, 2008, 8, 1258 DOI: 10.1039/b803212b
The content of this RSS Feed (c) The Royal Society of Chemistry
Daniel Brassard, Lidija Malic, Francois Normandin, Maryam Tabrizian, Teodor Veres
(Paper from Lab Chip)
Daniel Brassard, Lab Chip, 2008, 8, 1342 DOI: 10.1039/b803827a
The content of this RSS Feed (c) The Royal Society of Chemistry
Abstract The present study has numerically investigated two-dimensional electroosmotic flows in a microchannel with dielectric walls
of rectangle-waved surface roughness to understand the roughness effect. For the study, numerical simulations are performed
by employing the Nernst–Planck equation for the ionic species and the Poisson equation for the electric potential, together
with the traditional Navier–Stokes equation. Results show that the steady electroosmotic flow and ionic-species transport
in a microscale channel are well predicted by the Poisson–Nernst–Planck model and depend significantly on the shape of surface
roughness such as the amplitude and periodic length of wall wave. It is found that the fluid flows along the surface of waved
wall without involving any flow separation because of the very strong normal component of EDL (electric double layer) electric
field. The flow rate decreases exponentially with the amplitude of wall wave, whereas it increases linearly with the periodic
length. It is mainly due to the fact that the external electric-potential distribution plays a crucial role in driving the
electroosmotic flow through a microscale channel with surface roughness. Finally, the present results using the Poisson–Nernst–Planck
model are compared with those using the traditional Poisson–Boltzmann model which may be valid in these scales.
Content Type Journal Article
Category Research Paper
DOI 10.1007/s10404-008-0321-5
Authors
Sangmo Kang, Dong-A University Division of Mechanical Engineering 840, Hadan2-dong, Saha-gu Busan 604-714 South Korea
Yong Kweon Suh, Dong-A University Division of Mechanical Engineering 840, Hadan2-dong, Saha-gu Busan 604-714 South Korea
Abstract This study presents a new Y-channel design for measuring the zeta potential and surface conductance of a solid-liquid pairing
using the current monitoring technique. The new design improves the throughput and reliability of the testing apparatus since
the displacement between two solutions can be repeated many times without interfering with the experiments. It also increases
the accuracy of the measurement by producing sharper start and end transitions for the current–time plot of the solution displacement
process. In this design, efforts have been made to minimize the effects of electrolysis, Joule heating and undesired pressure
driven flow on the measurements. An improvement on the current–time slope analysis is also presented. The Y-channel design
was validated by comparing zeta potential measurements to published results. The zeta potential of several biological buffers
relevant to the microfluidic community in plasma treated PDMS/PDMS and PDMS/Glass microchannels are presented. Preliminary
studies of surface conductivity measurements using the Y-channel design were also conducted and are briefly discussed.
Content Type Journal Article
Category Research Paper
DOI 10.1007/s10404-008-0320-6
Authors
Zeyad A. Almutairi, University of Waterloo Department of Mechanical and Mechatronics Engineering 200 University Avenue West Waterloo ON N2L 3G1 Canada
Tomasz Glawdel, University of Waterloo Department of Mechanical and Mechatronics Engineering 200 University Avenue West Waterloo ON N2L 3G1 Canada
Carolyn L. Ren, University of Waterloo Department of Mechanical and Mechatronics Engineering 200 University Avenue West Waterloo ON N2L 3G1 Canada
David A. Johnson, University of Waterloo Department of Mechanical and Mechatronics Engineering 200 University Avenue West Waterloo ON N2L 3G1 Canada
The tumor-inhibitory effect of C60(OH)x was tested on the murine H22 hepatocarcinoma model. Doses of 0.2 and 1.0 mg kg-1 body weight both showed significant antitumor activity with tumor inhibition rates of 31.9 and 38.4%, respectively, when mice were treated for 17 consecutive days. The damnification of liver was prominently reduced. Furthermore, histological examination indicated that an envelope of fibroblasts and lymphocytes was formed surrounding tumor tissues in the C60(OH)x-treated group, which inhibited the infiltration of tumor to the neighboring normal skeleton muscle tissues. To understand the antitumor mechanism, the immunomodulatory activity of C60(OH)x was investigated. The results indicate that C60(OH)x enhances the phagocytosis of peritoneal macrophages and elevates the activity of arginase and acid phosphatase in vivo. The tumor necrosis factor alpha production of C60(OH)x-treated macrophages also increases in vitro. These results suggest that C60(OH)x can enhance the innate immunity of tumor-bearing mice, and therefore inhibits growth of the tumor.
Abstract A microfluidic device is presented with off-chip electrodes residing in a reservoir and connected via micro-capillaries to
the Y-shaped microfluidic channel. The device is tested by potentiometric measurements involving dual-stream laminar flow
of two aqueous solutions carrying different electrolytes at various concentrations. Open circuit potentials are measured for
a series of solutions of alkali metal chlorides and tetraalkylammonium chlorides as well as for dilute hydrochloric acid.
The open circuit potential for the microfluidic chip was calculated by taking into account the diffusion potential at finite
ionic strength as well as the potential difference introduced by the reference electrode system. The liquid junction potential
developed at the boundary of the co-flowing aqueous solutions may be manipulated to have greater or lesser relative contributions
to the measured open circuit potential based on use of electrolyte salts having cation and anion pairs of similar or dissimilar
mobilities in solution. A reasonable agreement between theoretical and experimental values of the open circuit potential is
observed for these situations. The results show that simple microfluidic structures possess a rich environment for exploration
and application of the solution chemistry of ions.
Content Type Journal Article
Category Research Paper
DOI 10.1007/s10404-008-0319-z
Authors
Jörg Strutwolf, University College Cork Tyndall National Institute Lee Maltings Cork Ireland
Abstract Traveling-wave electrohydrodynamic (EHD) micropumps can be incorporated into the package of an integrated circuit chip to
provide active cooling. They can also be used for fluid delivery in microdevices. The pump operates in the presence of a thermal
gradient through the fluid layer such that a gradient in electrical conductivity is established allowing ions to be induced.
These ions are driven by a traveling electric field. Such a traveling electric field can be realized in practice only via
discrete electrodes upon which the required voltages are imposed. The impact of using discrete electrodes to create the traveling
wave on the flow rates generated is explored through numerical modeling. The change in performance from an ideal sinusoidal
voltage boundary condition is quantified. The model is used to explore the widths of electrodes and the intervening isolation
regions that lead to optimized pumping. The influence of the choice of working fluid on the performance of the pump is determined
using an analytical model.
Content Type Journal Article
Category Research Paper
DOI 10.1007/s10404-008-0317-1
Authors
Brian D. Iverson, Purdue University NSF Cooling Technologies Research Center, School of Mechanical Engineering and Birck Nanotechnology Center 585 Purdue Mall West Lafayette IN 47907-2088 USA
Lorenzo Cremaschi, Oklahoma State University School of Mechanical and Aerospace Engineering 218 Engineering North Stillwater OK 74078 USA
Suresh V. Garimella, Purdue University NSF Cooling Technologies Research Center, School of Mechanical Engineering and Birck Nanotechnology Center 585 Purdue Mall West Lafayette IN 47907-2088 USA
Abstract A compact model for calculating damping, inertial, and spring forces in a perforated squeeze-film damper is reported. The
repetitive pressure patterns around each perforation are utilized by analyzing the visco-acoustic wave transmission around
the hole in a cylindrical volume, called perforation cell. The model is needed in applications where the acoustic wavelength
of the oscillation is comparable with the dimensions of the perforation cell. The model is constructed of acoustic impedance
two-ports. A novel model is derived for the air gap region, and a published two-port model is used for the hole. The impedances
for these two-ports are derived from the low reduced frequency model that is equivalent with linearized, harmonic Navier–Stokes
equations for acoustic wave propagation in thin channels. This model considers also the transition from the isothermal conditions
at low frequencies to the adiabatic ones at high frequencies. The dimensions of MEMS structures are considered using slip
conditions for velocities and temperatures. Also, an easy-to-use simplified model for frequencies where the squeeze number
and the Reynolds numbers are below unity is derived. The analytical compact model is verified with FEM simulations using a
harmonic solver for linearized Navier–Stokes equations with slip boundary conditions in a wide range of perforation ratios.
The maximum relative error in the damping coefficient in the simulated cases was 20% upto the first resonant frequency.
Content Type Journal Article
Category Research Paper
DOI 10.1007/s10404-008-0313-5
Authors
Timo Veijola, Helsinki University of Technology Department of Radio Science and Engineering P.O. Box 3000 02015 TKK Espoo Finland
Abstract Impedance microfluidic cytometry is a non-invasive, label-free technology that can characterize the dielectric properties
of single particles (beads/cells) at high speed. In this paper we show how digital signal processing methods are applied to
the impedance signals for noise removal and signal recovery in an impedance microfluidic cytometry. Two methods are used;
correlation to identify typical signals from a particle and for a noisier environment, an adaptive filter is used to remove
noise. The benefits of adaptive filtering are demonstrated quantitatively from the correlation coefficient and signal-to-noise
ratio. Finally, the adaptive filtering method is compared to the Savitzky–Golay filtering method.
Content Type Journal Article
Category Research Paper
DOI 10.1007/s10404-008-0315-3
Authors
Tao Sun, University of Southampton Nanoscale Systems Integration Group, School of Electronics and Computer Science Southampton SO17 1BJ UK
Cees van Berkel, Philips Research Laboratory Cross Oak Lane, Redhill Surrey RH1 5HA UK
Nicolas G. Green, University of Southampton Nanoscale Systems Integration Group, School of Electronics and Computer Science Southampton SO17 1BJ UK
Hywel Morgan, University of Southampton Nanoscale Systems Integration Group, School of Electronics and Computer Science Southampton SO17 1BJ UK
Abstract This paper describes a fundamental study on a pneumatic particle trap with a vibrator matrix. The particle trap device consisted
of pneumatic vibrators and a trap chamber used to trap a particle. The entire structure was fabricated from polydimethylsiloxane
(PDMS). The particle in the trap chamber was manipulated and trapped in the equilibrium region by exploiting the geometrical
symmetry of the vibrators. The x-axial velocity of the viscous fluid induced by the deformation of the flexible diaphragms was eliminated or minimized at
the center of two vibrators. Therefore, a particle could be trapped in the central capturing region by two or four vibrators.
The trapping of static and dynamic single particles was observed to verify the proposed operational method.
Content Type Journal Article
Category Short Communication
DOI 10.1007/s10404-008-0318-0
Authors
Ok Chan Jeong, Institute of Biomedical Engineering, INJE University Department of Biomedical Engineering Gimhae Korea
Satoshi Konishi, Ritsumeikan University Department of Micro System Technology Kusatsu Japan
Abstract This paper performs numerical and experimental investigations into electrokinetic instability (EKI) effects to accomplish
mixing of multiple solutions with different electric conductivities in a cross-shaped microchannel. This study considers two
multiple-species, namely two aqueous electrolyte solutions and three electrolyte solutions with conductivity ratios ranging
between 1 and 10, respectively. A stratified flow condition is formed when the intensity of the applied DC electrical field
is below a certain threshold value. However, as the intensity increased, various EKI phenomena are induced, including a series
of flow recirculations at the interfaces of neighboring species flows, a string of pearl-like flow structures aligned with
the low-conductivity species stream, and a wavy perturbation of the species interfaces. The EKI phenomena are clarified in
terms of the respective axial velocities and specie flow pressure gradients. In practice, the nature of the EKI effect depends
upon the relative directions of the conductivity gradients within the microchannel. Analyzing the EKI phenomena effects in
mixing multiple-species, it is found that the mixing performance obtained when the conductivity gradients are orientated in
opposing directions is higher than that achieved when the conductivity gradients are aligned. Furthermore, the optimal mixing
index is achieved when the conductivity gradients are directed away from one another (i.e. from the center of the microchannel
toward the microchannel walls) rather than toward one another (i.e. from the microchannel walls toward the center of the microchannel).
Content Type Journal Article
Category Research Paper
DOI 10.1007/s10404-008-0316-2
Authors
Win-Jet Luo, National Chin-Yi University of Technology Department of Refrigeration, Air Conditioning and Energy Engineering Taiping Taichung 411 Taiwan, ROC
Abstract The motion of a liquid inclusion inside a 1D microchannel filled with gas and externally heated is simulated. An incompressible
formulation is used for the liquid, while a low Mach approximation is considered for the gas flow. Gas–liquid interfaces are
captured using an Arbitrary Lagrangian Eulerian method. The whole liquid–gas system is shown to behave as a damped oscillator.
Natural frequency of the linearized system and associated eigenmodes are first identified. Forced oscillations are investigated
for different heating conditions (temperature or heat flux) at the microchannel ends. Detailed analyses are performed which
reveal the main thermo-mechanical effects involved in the oscillations. The relevant parameters governing the dynamics are
found out through a dimensionless analysis. Finally, heating conditions leading to non decaying oscillations of the liquid
inclusion are proposed.
Content Type Journal Article
Category Research Paper
DOI 10.1007/s10404-008-0308-2
Authors
M.-C. Duluc, LIMSI-CNRS B.P. 133 91403 Orsay Cedex France
O. P. Le Maître, LIMSI-CNRS B.P. 133 91403 Orsay Cedex France
V. Daru, LIMSI-CNRS B.P. 133 91403 Orsay Cedex France
Abstract Nanofluidic systems are attracting a great deal of interest due to their fundamental significance and potential applications
in chemistry, biology and physics. However, high fabrication cost, expensive equipments and complicated fabrication process
of most current fabrication techniques prevent lots of researchers from entering the nanofluidic field. Here we present a
quick, simple and cost-effective method for fabricating two-dimensional (2D) nanochannel in polycarbonate (PC) substrates.
Silica nanowires, taper-drawn from commercially available single-mode fiber were used as templates and embedded in the PC
substrate by hot embossing. The nanochannels were created after removing the nanowires by hydrofluoric acid (HF) etching.
Poly(dimethylsiloxane) (PDMS) was used to seal the nanochannel reversibly. Nanochannels with widths range from 100 to 900
nm and lengths up to several millimeters were obtained. Various nanostructures including integrated micro and nanochannels,
nanochannel array, bent nanochannel and cross-shaped nanochannel were fabricated and characterized by fluorescent microscope,
scanning electron microscope (SEM) and atomic force microscope (AFM).
Content Type Journal Article
Category Short Communication
DOI 10.1007/s10404-008-0314-4
Authors
Lei Zhang, Institute of Microanalytical Systems, Zhejiang University Department of Chemistry 310027 Hangzhou China
Fuxing Gu, Zhejiang University State Key Laboratory of Modern Optical Instrumentation, Department of Optical Engineering 310027 Hangzhou China
Limin Tong, Zhejiang University State Key Laboratory of Modern Optical Instrumentation, Department of Optical Engineering 310027 Hangzhou China
Xuefeng Yin, Institute of Microanalytical Systems, Zhejiang University Department of Chemistry 310027 Hangzhou China
Abstract Experiments were carried out in order to evaluate the conductance of tubes of circular cross section as a function of the
Knudsen number. The range of the rarefaction level spans from the free molecular flow to the continuum regime. A different
experimental approach was followed with respect to previous researches in that the mass flow rate was assigned and the corresponding
pressure drop was measured. Single tubes and a bundle of capillaries were adopted. The results are compared with the existing
experimental data and
