The Experts below are selected from a list of 4848 Experts worldwide ranked by ideXlab platform
Tony Jun Huang - One of the best experts on this subject based on the ideXlab platform.
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Microfluidic Hydrodynamic Focusing for synthesis of nanomaterials
Nano today, 2016Co-Authors: Adem Ozcelik, Christopher L. Grigsby, Yanhui Zhao, Feng Guo, Kam W. Leong, Tony Jun HuangAbstract:Microfluidics expands the synthetic space such as heat transfer, mass transport, and reagent consumption to conditions not easily achievable in conventional batch processes. Hydrodynamic Focusing in particular enables the generation and study of complex engineered nanostructures and new materials systems. In this review, we present an overview of recent progress in the synthesis of nanostructures and microfibers using microfluidic Hydrodynamic Focusing techniques. Emphasis is placed on distinct designs of flow Focusing methods and their associated mechanisms, as well as their applications in material synthesis, determination of reaction kinetics, and study of synthetic mechanisms.
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Shape-controlled synthesis of hybrid nanomaterials via three-dimensional Hydrodynamic Focusing.
ACS nano, 2014Co-Authors: Shikuan Yang, Kam W. Leong, Christopher L. Grigsby, Tony Jun HuangAbstract:Shape-controlled synthesis of nanomaterials through a simple, continuous, and low-cost method is essential to nanomaterials research toward practical applications. Hydrodynamic Focusing, with its advantages of simplicity, low-cost, and precise control over reaction conditions, has been used for nanomaterial synthesis. While most studies have focused on improving the uniformity and size control, few have addressed the potential of tuning the shape of the synthesized nanomaterials. Here we demonstrate a facile method to synthesize hybrid materials by three-dimensional Hydrodynamic Focusing (3D-HF). While keeping the flow rates of the reagents constant and changing only the flow rate of the buffer solution, the molar ratio of two reactants (i.e., tetrathiafulvalene (TTF) and HAuCl4) within the reaction zone varies. The synthesized TTF–Au hybrid materials possess very different and predictable morphologies. The reaction conditions at different buffer flow rates are studied through computational simulation, an...
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Three-Dimensional Hydrodynamic Focusing Method for Polyplex Synthesis
ACS nano, 2014Co-Authors: Christopher L. Grigsby, Kam W. Leong, Ahmad Ahsan Nawaz, Tony Jun HuangAbstract:Successful intracellular delivery of nucleic acid therapeutics relies on multiaspect optimization, one of which is formulation. While there has been ample innovation on chemical design of polymeric gene carriers, the same cannot be said for physical processing of polymer-DNA nanocomplexes (polyplexes). Conventional synthesis of polyplexes by bulk mixing depends on the operators' experience. The poorly controlled bulk mixing process may also lead to batch-to-batch variation and consequent irreproducibility. Here, we synthesize polyplexes by using a three-dimensional Hydrodynamic Focusing (3D-HF) technique in a single-layered, planar microfluidic device. Without any additional chemical treatment or postprocessing, the polyplexes prepared by the 3D-HF method show smaller size, slower aggregation rate, and higher transfection efficiency, while exhibiting reduced cytotoxicity compared to the ones synthesized by conventional bulk mixing. In addition, by introducing external acoustic perturbation, mixing can be further enhanced, leading to even smaller nanocomplexes. The 3D-HF method provides a simple and reproducible process for synthesizing high-quality polyplexes, addressing a critical barrier in the eventual translation of nucleic acid therapeutics.
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an integrated multiparametric flow cytometry chip using microfluidic drifting based three dimensional Hydrodynamic Focusing
Biomicrofluidics, 2012Co-Authors: Xiaole Mao, Sz Chin Steven Lin, Yanhui Zhao, Ahmad Ahsan Nawaz, Michael Ian Lapsley, Philip J Mccoy, Wafik S Eldeiry, Tony Jun HuangAbstract:In this work, we demonstrate an integrated, single-layer, miniature flow cytometry device that is capable of multi-parametric particle analysis. The device integrates both particle Focusing and detection components on-chip, including a “microfluidic drifting” based three-dimensional (3D) Hydrodynamic Focusing component and a series of optical fibers integrated into the microfluidic architecture to facilitate on-chip detection. With this design, multiple optical signals (i.e., forward scatter, side scatter, and fluorescence) from individual particles can be simultaneously detected. Experimental results indicate that the performance of our flow cytometry chip is comparable to its bulky, expensive desktop counterpart. The integration of on-chip 3D particle Focusing with on-chip multi-parametric optical detection in a single-layer, mass-producible microfluidic device presents a major step towards low-cost flow cytometry chips for point-of-care clinical diagnostics.
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Single-layer planar on-chip flow cytometer using microfluidic drifting based three-dimensional (3D) Hydrodynamic Focusing
Lab on a Chip, 2009Co-Authors: Xiaole Mao, Sz Chin Steven Lin, Cheng Dong, Tony Jun HuangAbstract:In this work, we demonstrate an on-chip microfluidic flow cytometry system based on a three-dimensional (3D) Hydrodynamic Focusing technique, microfluidic drifting. By inducing Dean flow in a curved microfluidic channel, microfluidic drifting can be used to Hydrodynamically focus cells or particles in the vertical direction and enables the 3D Hydrodynamic Focusing in a single-layer planar microfluidic device. Through theoretical calculation, numerical simulation, and experimental characterization, we found that the microfluidic drifting technique can be effectively applied to three-dimensionally focus microparticles with density and size equivalent to those of human CD4+ T lymphocytes. In addition, we developed a flow cytometry platform by integrating the 3D Focusing device with a laser-induced fluorescence (LIF) detection system. The system was shown to provide effective high-throughput flow cytometry measurements at a rate of greater than 1700 cells s(-1).
Frances S Ligler - One of the best experts on this subject based on the ideXlab platform.
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Data characterizing microfabricated human blood vessels created via Hydrodynamic Focusing
Data in brief, 2017Co-Authors: Kyle A. Divito, Frances S Ligler, Michael A. Daniele, Steven A. Roberts, André A. AdamsAbstract:This data article provides further detailed information related to our research article titled "Microfabricated Blood Vessels Undergo Neovascularization" (DiVito et al., 2017) [1], in which we report fabrication of human blood vessels using Hydrodynamic Focusing (HDF). Hydrodynamic Focusing with advection inducing chevrons were used in concert to encase one fluid stream within another, shaping the inner core fluid into 'bullseye-like" cross-sections that were preserved through click photochemistry producing streams of cellularized hollow 3-dimensional assemblies, such as human blood vessels (Daniele et al., 2015a, 2015b, 2014, 2016; Roberts et al., 2016) [2], [3], [4], [5], [6]. Applications for fabricated blood vessels span general tissue engineering to organ-on-chip technologies, with specific utility in in vitro drug delivery and pharmacodynamics studies. Here, we report data regarding the construction of blood vessels including cellular composition and cell positioning within the engineered vascular construct as well as functional aspects of the tissues.
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3D Hydrodynamic Focusing microfluidics for emerging sensing technologies.
Biosensors & bioelectronics, 2014Co-Authors: Michael A. Daniele, Darryl A. Boyd, David R. Mott, Frances S LiglerAbstract:While the physics behind laminar flows has been studied for 200 years, understanding of how to use parallel flows to augment the capabilities of microfluidic systems has been a subject of study primarily over the last decade. The use of one flow to focus another within a microfluidic channel has graduated from a two-dimensional to a three-dimensional process and the design principles are only now becoming established. This review explores the underlying principles for Hydrodynamic Focusing in three dimensions (3D) using miscible fluids and the application of these principles for creation of biosensors, separation of cells and particles for sample manipulation, and fabrication of materials that could be used for biosensors. Where sufficient information is available, the practicality of devices implementing fluid flows directed in 3D is evaluated and the advantages and limitations of 3D Hydrodynamic Focusing for the particular application are highlighted.
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design and fabrication of uniquely shaped thiol ene microfibers using a two stage Hydrodynamic Focusing design
Lab on a Chip, 2013Co-Authors: Darryl A. Boyd, A R Shields, Peter B Howell, Frances S LiglerAbstract:Microfluidic systems have advantages that are just starting to be realized for materials fabrication. In addition to the more common use for fabrication of particles, Hydrodynamic Focusing has been used to fabricate continuous polymer fibers. We have previously described such a microfluidics system which has the ability to generate fibers with controlled cross-sectional shapes locked in place by in situ photopolymerization. The previous fiber fabrication studies produced relatively simple round or ribbon shapes, demonstrated the use of a variety of polymers, and described the interaction between sheath-core flow-rate ratios used to control the fiber diameter and the impact on possible shapes. These papers documented the fact that no matter what the intended shape, higher flow-rate ratios produced rounder fibers, even in the absence of interfacial tension between the core and sheath fluids. This work describes how to fabricate the next generation of fibers predesigned to have a much more complex geometry, as exemplified by the "double anchor" shape. Critical to production of the pre-specified fibers with complex features was independent control over both the shape and the size of the fabricated microfibers using a two-stage Hydrodynamic Focusing system. Design and optimization of the channels was performed using finite element simulations and confocal imaging to characterize each of the two stages theoretically and experimentally. The resulting device design was then used to generate thiol-ene fibers with a unique double anchor shape. Finally, proof-of-principle functional experiments demonstrated the ability of the fibers to transport fluids and to interlock laterally.
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Hydrodynamic Focusing for impedance-based detection of specifically bound microparticles and cells: Implications of fluid dynamics on tunable sensitivity
Sensors and Actuators B-chemical, 2012Co-Authors: Gusphyl Justin, Joel P Golden, Mansoor Nasir, Aleksandra K. Denisin, Lisa C. Shriver-lake, Frances S LiglerAbstract:Abstract A 4-electrode impedance-based microfluidic sensor was designed to achieve tunable sensitivity, while simultaneously decreasing the channel clogging and nonspecific binding that often adversely impact device function. Hydrodynamic Focusing – a characteristic of laminar flow at low Reynold's number – provides highly controllable sensitivity in impedance-based microfluidic biosensors, by creating a “virtual” microchannel with soft walls and adjustable dimensions. Enhanced sensitivity, limited nonspecific binding, and a reduction in microchannel clogging have been achieved using Hydrodynamic Focusing within a 250 μm deep by 1 mm wide microchannel. The microfluidic sensor was able to detect microparticles as small as 5 μm in diameter specifically bound between co-planar platinum micro-electrodes. However, detection of submicron particles and E. coli cells in similar fashion proved to be challenging. A theoretical analysis of forces exerted by the fluids within the microchannel allowed specification of flow rates amenable to decreased nonspecific binding of interfering cells or microparticles, while ensuring minimal disruption to specifically bound targets. Simulations revealed that complex flow behavior of the Hydrodynamically focused streams around specifically bound micron-sized particles reduces sensitivity. An improved understanding is thus presented of the parameters that impact the sensitivity of impedance-based biosensors implementing Hydrodynamic Focusing and specific target binding.
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Hydrodynamic Focusing a versatile tool
Analytical and Bioanalytical Chemistry, 2012Co-Authors: Joel P Golden, Gusphyl Justin, Mansoor Nasir, Frances S LiglerAbstract:The control of Hydrodynamic Focusing in a microchannel has inspired new approaches for microfluidic mixing, separations, sensors, cell analysis, and microfabrication. Achieving a flat interface between the Focusing and focused fluids is dependent on Reynolds number and device geometry, and many Hydrodynamic Focusing systems can benefit from this understanding. For applications where a specific cross-sectional shape is desired for the focused flow, advection generated by grooved structures in the channel walls can be used to define the shape of the focused flow. Relative flow rates of the focused flow and Focusing streams can be manipulated to control the cross-sectional area of the focused flows. This paper discusses the principles for defining the shape of the interface between the focused and Focusing fluids and provides examples from our lab that use Hydrodynamic Focusing for impedance-based sensors, flow cytometry, and microfabrication to illustrate the breadth of opportunities for introducing new capabilities into microfluidic systems. We evaluate each example for the advantages and limitations integral to utilization of Hydrodynamic Focusing for that particular application.
Xiaole Mao - One of the best experts on this subject based on the ideXlab platform.
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Sub-micrometer-precision, three-dimensional (3D) Hydrodynamic Focusing via “microfluidic drifting”
Lab on a chip, 2013Co-Authors: Ahmad Ahsan Nawaz, Sz Chin Steven Lin, Xiaole Mao, Yanhui Zhao, Feng Guo, Xiangjun Zhang, Joseph Rufo, Michael Ian Lapsley, J. Philip MccoyAbstract:In this article, we demonstrate single-layered, “microfluidic drifting” based three-dimensional (3D) Hydrodynamic Focusing devices with particle/cell focal positioning approaching submicron precision along both lateral and vertical directions. By systematically optimizing channel geometries and sample/sheath flow rates, a series of “microfluidic drifting” based 3D Hydrodynamic Focusing devices with different curvature angles are designed and fabricated. Their performances are then evaluated using confocal microscopy, fast camera imaging, and side-view imaging techniques. Using a device with a curvature angle of 180°, we have achieved a standard deviation of ±0.45 μm in particle focal position and a coefficient of variation (CV) of 2.37% in flow cytometric measurements. To the best of our knowledge, this is the best CV that has been achieved using a microfluidic flow cytometry device. Moreover, the device showed the capability to distinguish 8 peaks when subjected to a stringent 8-peak rainbow calibration test, signifying the ability to perform sensitive, accurate tests similar to commercial flow cytometers. We have further tested and validated our device by detection of HEK-293 cells. With its advantages in simple fabrication (i.e., single-layered device), precise 3D Hydrodynamic Focusing (i.e., submicrometer precision along both lateral and vertical directions), and high detection resolution (i.e., low CV), our method could serve as an important basis for high-performance, mass-producible microfluidic flow cytometry.
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an integrated multiparametric flow cytometry chip using microfluidic drifting based three dimensional Hydrodynamic Focusing
Biomicrofluidics, 2012Co-Authors: Xiaole Mao, Sz Chin Steven Lin, Yanhui Zhao, Ahmad Ahsan Nawaz, Michael Ian Lapsley, Philip J Mccoy, Wafik S Eldeiry, Tony Jun HuangAbstract:In this work, we demonstrate an integrated, single-layer, miniature flow cytometry device that is capable of multi-parametric particle analysis. The device integrates both particle Focusing and detection components on-chip, including a “microfluidic drifting” based three-dimensional (3D) Hydrodynamic Focusing component and a series of optical fibers integrated into the microfluidic architecture to facilitate on-chip detection. With this design, multiple optical signals (i.e., forward scatter, side scatter, and fluorescence) from individual particles can be simultaneously detected. Experimental results indicate that the performance of our flow cytometry chip is comparable to its bulky, expensive desktop counterpart. The integration of on-chip 3D particle Focusing with on-chip multi-parametric optical detection in a single-layer, mass-producible microfluidic device presents a major step towards low-cost flow cytometry chips for point-of-care clinical diagnostics.
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Single-layer planar on-chip flow cytometer using microfluidic drifting based three-dimensional (3D) Hydrodynamic Focusing
Lab on a Chip, 2009Co-Authors: Xiaole Mao, Sz Chin Steven Lin, Cheng Dong, Tony Jun HuangAbstract:In this work, we demonstrate an on-chip microfluidic flow cytometry system based on a three-dimensional (3D) Hydrodynamic Focusing technique, microfluidic drifting. By inducing Dean flow in a curved microfluidic channel, microfluidic drifting can be used to Hydrodynamically focus cells or particles in the vertical direction and enables the 3D Hydrodynamic Focusing in a single-layer planar microfluidic device. Through theoretical calculation, numerical simulation, and experimental characterization, we found that the microfluidic drifting technique can be effectively applied to three-dimensionally focus microparticles with density and size equivalent to those of human CD4+ T lymphocytes. In addition, we developed a flow cytometry platform by integrating the 3D Focusing device with a laser-induced fluorescence (LIF) detection system. The system was shown to provide effective high-throughput flow cytometry measurements at a rate of greater than 1700 cells s(-1).
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High-throughput on-chip flow cytometry system using “microfluidic drifting” based three-dimensional (3D) Hydrodynamic Focusing
TRANSDUCERS 2009 - 2009 International Solid-State Sensors Actuators and Microsystems Conference, 2009Co-Authors: Xiaole Mao, Steven Sz-chin Lin, Tony Jun HuangAbstract:In this work we demonstrate the application of a three-dimensional (3D) Hydrodynamic Focusing technique, “microfluidic drifting” in the development of a miniaturized on-chip flow cytometry system. “Microfluidic drifting” utilizes viscous drag of Dean flow induced in a curved microfluidic channel to realize 3D Hydrodynamic Focusing in a single layer planar microfluidic device. Through force scaling analysis, numerical study, and experimental characterization, we show this technique can be successfully applied to focus large microparticles such as biological cells. A laser-induced fluorescence (LIF) detection system was incorporated with the 3D Focusing device and a high-throughput (1700 cells/s) cell detection was demonstrated.
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microfluidic drifting implementing three dimensional Hydrodynamic Focusing with a single layer planar microfluidic device
Lab on a Chip, 2007Co-Authors: Xiaole Mao, John Robert Waldeisen, Tony Jun HuangAbstract:We introduce a novel fluid manipulation technique named “microfluidic drifting” to enable three-dimensional (3D) Hydrodynamic Focusing with a simple single-layer planar microfluidic device.
Nam-trung Nguyen - One of the best experts on this subject based on the ideXlab platform.
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Electroosmotic control of width and position of liquid streams in Hydrodynamic Focusing
Microfluidics and Nanofluidics, 2009Co-Authors: Teck Neng Wong, Nam-trung NguyenAbstract:This paper presents theoretical and experimental investigations on electroosmotic control of stream width in Hydrodynamic Focusing. In the experiments, three liquids (aqueous NaCl, aqueous glycerol and aqueous NaCl) are introduced by syringe pumps to flow side by side in a straight rectangular microchannel. External electric fields are applied on the two aqueous NaCl streams. Under the same inlet volumetric flow rates, the applied electric fields are varied to control the interface positions and consequently the width of the focused aqueous glycerol stream. The electroosmotic effect on the width of the aqueous glycerol is measured using fluorescence imaging technique. The electroosmotic effect under different flow rates, different viscosity, and aspect ratio are investigated. The results indicate that the electroosmotic effect on the pressure-driven flow becomes weaker with the increase in flow rates, viscosity ratio or aspect ratio of the channel. The measured results of the focused width of the non-conducting fluid agree well with the analytical model.
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Microfluidic rheometer based on Hydrodynamic Focusing
Measurement Science and Technology, 2008Co-Authors: Nam-trung Nguyen, Yit Fatt Yap, Agung SumargoAbstract:This paper reports the concept and the optimization of a microfluidic rheometer based on Hydrodynamic Focusing. In our microfluidic rheometer, a sample stream is sandwiched between two sheath streams. The width of the middle stream depends on the viscosity ratio and the flow rate ratio of the liquids involved. Fixing the flow rate ratio and using a known Newtonian liquid for the sheath streams, the viscosity and the shear stress of the sample stream can be determined by measuring its width and using a prediction algorithm that uses the known channel geometries, fluid properties, flow rates and the focused width as input parameters. The optimization reveals that a measurement channel with a high aspect ratio is more suitable for a sample liquid with viscosity higher than the reference value. For a sample liquid with viscosity of the same order of magnitude or lower than the reference, a low aspect ratio is more suitable. Furthermore, the measurement range and the relative error can be improved by adjusting the flow rate ratio between the core stream and the sheath stream. A microfluidic device was fabricated in polymethylmethacrylate (PMMA). Using this device, viscosities of deionized (DI) water and polyethylene oxide (PEO) solutions were measured and compared with results obtained from a commercial rheometer.
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Mixing in microchannels based on Hydrodynamic Focusing and time-interleaved segmentation: modeling and experiment
BioMEMS and Nanotechnology II, 2005Co-Authors: Nam-trung Nguyen, Xiaoyang HuangAbstract:This paper reports a new mixing concept in microscale using Hydrodynamic Focusing and sequential segmentation. Both Focusing and segmentation were used in the present study to reduce mixing path, to shorten mixing time, and to enhance mixing quality. Transversal mixing path is reduced by Hydrodynamic Focusing, while sequential segmentation shortens the axial mixing path. Assuming the same viscosity in the different streams, the focused width can be adjusted by the flow rate ratio. The axial mixing path can be controlled by the switching frequency of the inlet valves and the mean velocity of the flow. Both flow rate ratio and pulse width modulation of the switching signal can adjust the desired mixing ratio. This paper first presents a time-dependent two-dimensional analytical model for the mixing concept. This model considers an arbitrary mixing ratio between solute and solvent as well as the axial Taylor-Aris dispersion. A polymeric micromixer was designed and fabricated by CO2 laser micromachining and hot lamination. Sequential segmentation was realized by two piezoelectric valves. The sheath streams for Hydrodynamic Focusing are introduced through other two inlets. We also designed a measurement system that can synchronize of the mixer's switching signal with the camera's trigger signal. The system allows our relatively slow and low-resolution CCD camera to freeze and to capture a large transient concentration field. The concentration profile along the mixing channel agrees qualitatively well with the analytical model.
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Mixing in microchannels based on Hydrodynamic Focusing and time-interleaved segmentation: modelling and experiment.
Lab on a chip, 2005Co-Authors: Nam-trung Nguyen, Xiaoyang HuangAbstract:This paper theoretically and experimentally investigates a micromixer based on combined Hydrodynamic Focusing and time-interleaved segmentation. Both Hydrodynamic Focusing and time-interleaved segmentation are used in the present study to reduce mixing path, to shorten mixing time, and to enhance mixing quality. While Hydrodynamic Focusing reduces the transversal mixing path, time-interleaved sequential segmentation shortens the axial mixing path. With the same viscosity in the different streams, the focused width can be adjusted by the flow rate ratio. The axial mixing path or the segment length can be controlled by the switching frequency and the mean velocity of the flow. Mixing ratio can be controlled by both flow rate ratio and pulse width modulation of the switching signal. This paper first presents a time-dependent two-dimensional analytical model for the mixing concept. The model considers an arbitrary mixing ratio between solute and solvent as well as the axial Taylor–Aris dispersion. A micromixer was designed and fabricated based on lamination of four polymer layers. The layers were machined using a CO2 laser. Time-interleaved segmentation was realized by two piezoelectric valves. The sheath streams for Hydrodynamic Focusing are introduced through the other two inlets. A special measurement set-up was designed with synchronization of the mixer's switching signal and the camera's trigger signal. The set-up allows a relatively slow and low-resolution CCD camera to freeze and to capture a large transient concentration field. The concentration profile along the mixing channel agrees qualitatively well with the analytical model. The analytical model and the device promise to be suitable tools for studying Taylor–Aris dispersion near the entrance of a flat microchannel.
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Hydrodynamic Focusing in microchannels under consideration of diffusive dispersion: theories and experiments
Sensors and Actuators B: Chemical, 2005Co-Authors: Nam-trung NguyenAbstract:This paper investigates Hydrodynamic Focusing inside a microchannel. Hydrodynamic Focusing has a number of applications in microfluidics such as micromixer, microcytometer, fluidic switch, and cell infection. In contrast to most of the previous works, Hydrodynamic Focusing phenomenon in this study is described analytically with a two-phase Navier–Stokes equation system. The model considers the effect of the different viscosities of the sample stream and the sheath streams. Based on this theory, the width of the sample flow cannot only be adjusted by the flow rates but also by the viscosity ratio between the sheath stream and the sample stream. Furthermore, the effect of diffusive dispersion between the sheath stream and the sample stream is investigated analytically and numerically. This effect is important for applications such as mixing and cell infection. The velocity field and concentration field of Hydrodynamic Focusing was measured using fluorescent techniques. Micro particle image velocimetry (micro-PIV) was used for measuring the velocity of the three streams quantitatively, while the concentration field was evaluated from fluorescent images. The results presented in the paper are fundamental for the design of Hydrodynamic Focusing in microfluidics.
Joel P Golden - One of the best experts on this subject based on the ideXlab platform.
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Hydrodynamic Focusing for impedance-based detection of specifically bound microparticles and cells: Implications of fluid dynamics on tunable sensitivity
Sensors and Actuators B-chemical, 2012Co-Authors: Gusphyl Justin, Joel P Golden, Mansoor Nasir, Aleksandra K. Denisin, Lisa C. Shriver-lake, Frances S LiglerAbstract:Abstract A 4-electrode impedance-based microfluidic sensor was designed to achieve tunable sensitivity, while simultaneously decreasing the channel clogging and nonspecific binding that often adversely impact device function. Hydrodynamic Focusing – a characteristic of laminar flow at low Reynold's number – provides highly controllable sensitivity in impedance-based microfluidic biosensors, by creating a “virtual” microchannel with soft walls and adjustable dimensions. Enhanced sensitivity, limited nonspecific binding, and a reduction in microchannel clogging have been achieved using Hydrodynamic Focusing within a 250 μm deep by 1 mm wide microchannel. The microfluidic sensor was able to detect microparticles as small as 5 μm in diameter specifically bound between co-planar platinum micro-electrodes. However, detection of submicron particles and E. coli cells in similar fashion proved to be challenging. A theoretical analysis of forces exerted by the fluids within the microchannel allowed specification of flow rates amenable to decreased nonspecific binding of interfering cells or microparticles, while ensuring minimal disruption to specifically bound targets. Simulations revealed that complex flow behavior of the Hydrodynamically focused streams around specifically bound micron-sized particles reduces sensitivity. An improved understanding is thus presented of the parameters that impact the sensitivity of impedance-based biosensors implementing Hydrodynamic Focusing and specific target binding.
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Hydrodynamic Focusing a versatile tool
Analytical and Bioanalytical Chemistry, 2012Co-Authors: Joel P Golden, Gusphyl Justin, Mansoor Nasir, Frances S LiglerAbstract:The control of Hydrodynamic Focusing in a microchannel has inspired new approaches for microfluidic mixing, separations, sensors, cell analysis, and microfabrication. Achieving a flat interface between the Focusing and focused fluids is dependent on Reynolds number and device geometry, and many Hydrodynamic Focusing systems can benefit from this understanding. For applications where a specific cross-sectional shape is desired for the focused flow, advection generated by grooved structures in the channel walls can be used to define the shape of the focused flow. Relative flow rates of the focused flow and Focusing streams can be manipulated to control the cross-sectional area of the focused flows. This paper discusses the principles for defining the shape of the interface between the focused and Focusing fluids and provides examples from our lab that use Hydrodynamic Focusing for impedance-based sensors, flow cytometry, and microfabrication to illustrate the breadth of opportunities for introducing new capabilities into microfluidic systems. We evaluate each example for the advantages and limitations integral to utilization of Hydrodynamic Focusing for that particular application.
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Hydrodynamic Focusing—a versatile tool
Analytical and Bioanalytical Chemistry, 2012Co-Authors: Joel P Golden, Mansoor Nasir, Gusphyl A. Justin, Frances S LiglerAbstract:The control of Hydrodynamic Focusing in a microchannel has inspired new approaches for microfluidic mixing, separations, sensors, cell analysis, and microfabrication. Achieving a flat interface between the Focusing and focused fluids is dependent on Reynolds number and device geometry, and many Hydrodynamic Focusing systems can benefit from this understanding. For applications where a specific cross-sectional shape is desired for the focused flow, advection generated by grooved structures in the channel walls can be used to define the shape of the focused flow. Relative flow rates of the focused flow and Focusing streams can be manipulated to control the cross-sectional area of the focused flows. This paper discusses the principles for defining the shape of the interface between the focused and Focusing fluids and provides examples from our lab that use Hydrodynamic Focusing for impedance-based sensors, flow cytometry, and microfabrication to illustrate the breadth of opportunities for introducing new capabilities into microfluidic systems. We evaluate each example for the advantages and limitations integral to utilization of Hydrodynamic Focusing for that particular application.
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Hydrodynamic Focusing of conducting fluids for conductivity-based biosensors.
Biosensors and Bioelectronics, 2009Co-Authors: Mansoor Nasir, Joel P Golden, Daniel A. Ateya, Diana Burk, Frances S LiglerAbstract:Hydrodynamic Focusing of a conducting fluid by a non-conducting fluid to form a constricted current path between two sensing electrodes is implemented in order to enhance the sensitivity of a 4-electrode conductance-based biosensor. The sensor has a simple two-inlet T-junction design and performs four-point conductivity measurements to detect particles immobilized between the sensing electrode pair. Computational simulations conducted in conjunction with experimental flow studies using confocal microscopy show that a flat profile for the focused layer is dependent on the Reynolds number for the chosen flow parameters. The results also indicate that a flat focused layer is desirable for both increased sensitivity as well as surface-binding efficiency. Proof of concept for conductance measurements in a Hydrodynamically focused conducting fluid was demonstrated with entrapped magnetic beads.