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Analysis of Electric Fields inside Microchannels and Single Cell Electrical Lysis with a Microfluidic Device  [PDF]
Bashir I. Morshed,Maitham Shams,Tofy Mussivand
Micromachines , 2013, DOI: 10.3390/mi4020243
Abstract: Analysis of electric fields generated inside the microchannels of a microfluidic device for electrical lysis of biological cells along with experimental verification are presented. Electrical lysis is the complete disintegration of cell membranes, due to a critical level of electric fields applied for a critical duration on a biological cell. Generating an electric field inside a microchannel of a microfluidic device has many advantages, including the efficient utilization of energy and low-current requirement. An ideal microchannel model was compared with a practical microchannel model using a finite element analysis tool that suggests that the overestimation error can be over 10%, from 2.5 mm or smaller, in the length of a microchannel. Two analytical forms are proposed to reduce this overestimation error. Experimental results showed that the high electric field is confined only inside the microchannel that is in agreement with the simulation results. Single cell electrical lysis was conducted with a fabricated microfluidic device. An average of 800 V for seven seconds across an 8 mm-long microchannel with the dimension of 100 μm × 20 μm was required for lysis, with electric fields exceeding 100 kV/m and consuming 300 mW.
Using electrowetting to control interface motion in patterned microchannels  [PDF]
B. M. Mognetti,J. M. Yeomans
Physics , 2010,
Abstract: We use mesoscale simulations to demonstrate the feasibility of a novel microfluidic valve, which exploits Gibbs' pinning in microchannels patterned by posts or ridges, together with electrowetting.
Cell Trapping Utilizing Insulator-based Dielectrophoresis in The Open-Top Microchannels  [PDF]
Chun-Ping Jen,Yao-Hung Huang,Teng-Wen Chen
Computer Science , 2008,
Abstract: The ability to manipulate or separate a biological small particle, such as a living cell and embryo, is fundamental needed to many biological and medical applications. The insulator-based dielectrophoresis (iDEP) trapping is composed of conductless tetragon structures in micro-chip. In this study, a lower conductive material of photoresist was adopted as a structure in open-top microchannel instead of a metallic wire to squeeze the electric field in a conducting solution, therefore, creating a high field gradient with a local maximum. The microchip with the open-top microchannels was designed and fabricated herein. The insulator-based DEP trapping microchip with the open-top microchannels was designed and fabricated in this work. The cells trapped by DEP force could be further treated or cultured in the open-top microchannel ; however, those trapped in the microchip with enclosed microchannels could not be proceeded easily.
Fabrication and Application of a Novel Cell Culture Microchip

Jianbo Shao,Lei Wu,Qinghui Jin,Jianlong Zhao,
,Lei Wu,金庆辉,Jianlong Zhao

生物工程学报 , 2008,
Abstract: In this article, a cell culture microchip was fabricated on the SU-8 mold based on polymer-MEMS process. In the microchip, the cell culture area was separated with microchannel by a microgap, which kept the cell culture area independent, but also regulated the micro-environment of extracellular matrix by the microfluidic flow. The cell culture microchip provided a new platform for cell research.
The effects of heat treatment on microfluidic devices fabricated in silica glass by femtosecond lasers

Li Yan,Qu Shi-Liang,

中国物理 B , 2012,
Abstract: We fabricated complex microfluidic devices in silica glass by water-assisted femtosecond laser ablation and subsequent heat treatment. The experimental results show that after heat treatment, the diameter of the microchannels is significantly reduced and the internal surface roughness is improved. The diameters of the fabricated microchannels can be modulated by changing the annealing temperature and the annealing time. During annealing, the temperature affects the diameter and shape of the protrusions in microfluidic devices very strongly, and these changes are mainly caused by uniform expansion and the action of surface tension.
Microfluidic Devices: Useful Tools for Bioprocess Intensification  [PDF]
Marco P.C. Marques,Pedro Fernandes
Molecules , 2011, DOI: 10.3390/molecules16108368
Abstract: The dawn of the new millennium saw a trend towards the dedicated use of microfluidic devices for process intensification in biotechnology. As the last decade went by, it became evident that this pattern was not a short-lived fad, since the deliverables related to this field of research have been consistently piling-up. The application of process intensification in biotechnology is therefore seemingly catching up with the trend already observed in the chemical engineering area, where the use of microfluidic devices has already been upgraded to production scale. The goal of the present work is therefore to provide an updated overview of the developments centered on the use of microfluidic devices for process intensification in biotechnology. Within such scope, particular focus will be given to different designs, configurations and modes of operation of microreactors, but reference to similar features regarding microfluidic devices in downstream processing will not be overlooked. Engineering considerations and fluid dynamics issues, namely related to the characterization of flow in microchannels, promotion of micromixing and predictive tools, will also be addressed, as well as reflection on the analytics required to take full advantage of the possibilities provided by microfluidic devices in process intensification. Strategies developed to ease the implementation of experimental set-ups anchored in the use of microfluidic devices will be briefly tackled. Finally, realistic considerations on the current advantages and limitation on the use of microfluidic devices for process intensification, as well as prospective near future developments in the field, will be presented.
Determinants of Leukocyte Margination in Rectangular Microchannels  [PDF]
Abhishek Jain, Lance L. Munn
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0007104
Abstract: Microfabrication of polydimethylsiloxane (PDMS) devices has provided a new set of tools for studying fluid dynamics of blood at the scale of real microvessels. However, we are only starting to understand the power and limitations of this technology. To determine the applicability of PDMS microchannels for blood flow analysis, we studied white blood cell (WBC) margination in channels of various geometries and blood compositions. We found that WBCs prefer to marginate downstream of sudden expansions, and that red blood cell (RBC) aggregation facilitates the process. In contrast to tubes, WBC margination was restricted to the sidewalls in our low aspect ratio, pseudo-2D rectangular channels and consequently, margination efficiencies of more than 95% were achieved in a variety of channel geometries. In these pseudo-2D channels blood rheology and cell integrity were preserved over a range of flow rates, with the upper range limited by the shear in the vertical direction. We conclude that, with certain limitations, rectangular PDMS microfluidic channels are useful tools for quantitative studies of blood rheology.
Clogging by sieving in microchannels: Application to the detection of contaminants in colloidal suspensions  [PDF]
Alban Sauret,Erin C. Barney,Adeline Perro,Emmanuel Villermaux,Howard A. Stone,Emilie Dressaire
Physics , 2014, DOI: 10.1063/1.4893459
Abstract: We report on a microfluidic method that allows measurement of a small concentration of large contaminants in suspensions of solid micrometer-scale particles. To perform the measurement, we flow the colloidal suspension through a series of constrictions, i.e. a microchannel of varying cross-section. We show and quantify the role of large contaminants in the formation of clogs at a constriction and the growth of the resulting filter cake. By measuring the time interval between two clogging events in an array of parallel microchannels, we are able to estimate the concentration of contaminants whose size is selected by the geometry of the microfluidic device. This technique for characterizing colloidal suspensions offers a versatile and rapid tool to explore the role of contaminants on the properties of the suspensions.
Coherence in Microchip Traps  [PDF]
Philipp Treutlein,Peter Hommelhoff,Tilo Steinmetz,Theodor W. H?nsch,Jakob Reichel
Physics , 2003, DOI: 10.1103/PhysRevLett.92.203005
Abstract: We report the coherent manipulation of internal states of neutral atoms in a magnetic microchip trap. Coherence lifetimes exceeding 1 s are observed with atoms at distances of $5-130 \mu$m from the microchip surface. The coherence lifetime in the chip trap is independent of atom-surface distance within our measurement accuracy, and agrees well with the results of similar measurements in macroscopic magnetic traps. Due to the absence of surface-induced decoherence, a miniaturized atomic clock with a relative stability in the $10^{-13}$ range can be realized. For applications in quantum information processing, we propose to use microwave near-fields in the proximity of chip wires to create potentials that depend on the internal state of the atoms.
Kinetic ELISA in Microfluidic Channels  [PDF]
Naoki Yanagisawa,Debashis Dutta
Biosensors , 2011, DOI: 10.3390/bios1020058
Abstract: In this article, we describe the kinetic ELISA of Blue Tongue and Epizootic Hemorrhagic Disease viral antibodies in microfluidic channels by monitoring the rate of generation of the enzyme reaction product under static conditions. It has been shown that this format of the immunoassay allows very reliable quantitation of the target species using inexpensive glass microchips and a standard epifluorescence microscope system coupled to a CCD camera. For the viral antibodies assayed here, the limit of detection (LOD) for the analyte concentration in our microchips was established to be 3–5 times lower than that obtained on commercial microwell plates using a fiftieth of the sample volume and less than a third of the incubation time. Our analyses further show that when compared to the end-point ELISA format, the kinetic mode of this assay yields an improvement in the LOD by over an order of magnitude in microfluidic devices. This benefit is primarily realized as the observed variation in the background fluorescence (signal at the start of the enzyme reaction period) was significantly larger than that in the rate of signal generation upon repeating these assays in different microchannels/microchips. Because the kinetic ELISA results depend only on the latter quantity, the noise level in them was substantially lower compared to that in its end-point counterpart in which the absolute fluorescence measurements are of greater significance. While a similar benefit was also recorded through implementation of kinetic ELISAs on the microwell platform, the improvement in LOD registered in that system was not as significant as was observed in the case of microfluidic assays.
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