scholarly journals A Numerical Investigation of Enhancing Microfluidic Heterogeneous Immunoassay on Bipolar Electrodes Driven by Induced-Charge Electroosmosis in Rotating Electric Fields

Micromachines ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 739
Author(s):  
Zhenyou Ge ◽  
Hui Yan ◽  
Weiyu Liu ◽  
Chunlei Song ◽  
Rui Xue ◽  
...  
Keyword(s):  
Electric Fields ◽  
Dimensional Space ◽  
Microfluidic Channel ◽  
Convective Transport ◽  
Base Flow ◽  
Working Fluid ◽  
Binding Reaction ◽  
Induced Charge ◽  
Heterogeneous Immunoassay ◽  
Floating Electrode

A unique approach is proposed to boost on-chip immuno-sensors, for instance, immunoassays, wherein an antibody immobilized on the walls of a microfluidic channel binds specifically to an antigen suspended freely within a working fluid. The performance of these sensors can be limited in both susceptibility and response speed by the slow diffusive mass transfer of the analyte to the binding surface. Under appropriate conditions, the binding reaction of these heterogeneous immuno-assays may be enhanced by electroconvective stirring driven by external AC electric fields to accelerate the translating motion of antigens towards immobilized antibodies. To be specific, the phenomenon of induced-charge electroosmosis in a rotating electric field (ROT-ICEO) is fully utilized to stir analyte in the vicinity of the functionalized surface of an ideally polarizable floating electrode in all directions inside a tri-dimensional space. ROT-ICEO appears as a consequence of the action of a circularly-polarized traveling wave signal on its own induced rotary Debye screening charge within a bipolar induced double layer formed on the central floating electrode, and thereby the pertinent electrokinetic streamlines exhibit a radially converging pattern that greatly facilitates the convective transport of receptor towards the ligand. Numerical simulations indicate that ROT-ICEO can enhance the antigen–antibody binding reaction more effectively than convectional nonlinear electroosmosis driven by standing wave AC signals. The effectiveness of ROT-ICEO micro-stirring is strongly dependent on the Damkohler number as well as the Peclet number if the antigens are carried by a continuous base flow. Our results provide a promising way for achieving a highly efficient heterogeneous immunoassay in modern micro-total-analytical systems.

scholarly journals Asymmetrical Induced Charge Electroosmotic Flow on a Herringbone Floating Electrode and Its Application in a Micromixer

Micromachines ◽  
2018 ◽  
Vol 9 (8) ◽  
pp. 391 ◽  
Author(s):  
Qingming Hu ◽  
Jianhua Guo ◽  
Zhongliang Cao ◽  
Hongyuan Jiang
Keyword(s):  
Electrode Surface ◽  
Slip Velocity ◽  
Fluid Velocity ◽  
Laminar Flows ◽  
Fluid Mixing ◽  
Electrode Pair ◽  
Great Opportunity ◽  
Mixing Performance ◽  
Induced Charge ◽  
Floating Electrode

Enhancing mixing is of significant importance in microfluidic devices characterized by laminar flows and low Reynolds numbers. An asymmetrical induced charge electroosmotic (ICEO) vortex pair generated on the herringbone floating electrode can disturb the interface of two-phase fluids and deliver the fluid transversely, which could be exploited to accomplish fluid mixing between two neighbouring fluids in a microscale system. Herein we present a micromixer based on an asymmetrical ICEO flow induced above the herringbone floating electrode array surface. We investigate the average transverse ICEO slip velocity on the Ridge/Vee/herringbone floating electrode and find that the microvortex generated on the herringbone electrode surface has good potential for mixing the miscible liquids in microfluidic systems. In addition, we explore the effect of applied frequencies and bulk conductivity on the slip velocity above the herringbone floating electrode surface. The high dependence of mixing performance on the floating electrode pair numbers is analysed simultaneously. Finally, we investigate systematically voltage intensity, applied frequencies, inlet fluid velocity and liquid conductivity on the mixing performance of the proposed device. The microfluidic micromixer put forward herein offers great opportunity for fluid mixing in the field of micro total analysis systems.

Evolution of picosecond surface electric fields generated by photon-induced charge emission from La0.67 Sr0.33MnO3 films

2020 ◽  
Vol 102 (2) ◽  
Author(s):  
Runze Li ◽  
Pengfei Zhu ◽  
Haijuan Zhang ◽  
Yao Wang ◽  
Jie Chen ◽  
...  
Keyword(s):  
Electric Fields ◽  
Induced Charge

Flow Field Analysis of Dielectrophoretically-Suspended Particles

2007 ◽  
Author(s):  
Stuart J. Williams ◽  
Steven T. Wereley
Keyword(s):  
Electric Fields ◽  
Particle Image ◽  
Fluid Velocity ◽  
Microfluidic Channel ◽  
Velocity Fields ◽  
Field Analysis ◽  
Tracer Particles ◽  
Image Velocimetry ◽  
Flow Field Analysis ◽  
Complete Investigation

Understanding the fluid dynamics around a particle in suspension is important for a complete investigation of many hydrodynamic phenomena, including microfluidic models. A novel tool that has been used to analyze fluid velocity fields in microfluidics is micro-resolution particle image velocimetry (μPIV) [1]. Dielectrophoresis (DEP) is a technique that can translate and trap particles by induced polarization in the presence of nonuniform electric fields. In this paper, DEP has been used to capture and suspend a single 10.1μm diameter spherical particle in a microfluidic channel. μPIV is then used with smaller tracer particles (0.5μm) to investigate the hydrodynamics of fluid flow past the trapped particle.

scholarly journals Fabrication of a Pneumatic Microparticle Concentrator

Micromachines ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 40
Author(s):  
Jun Ho Jang ◽  
Ok Chan Jeong
Keyword(s):  
Three Dimensional ◽  
Fem Simulation ◽  
Particle Diameter ◽  
Microfluidic Channel ◽  
Solid Particles ◽  
Working Fluid ◽  
Operating Pressure ◽  
Fluidic Channel ◽  
Outlet Port ◽  
Pneumatic Valves

We developed a microfluidic platform employing (normally open) pneumatic valves for particle concentration. The device features a three-dimensional network with a curved fluidic channel and three pneumatic valves (a sieve valve (Vs) that concentrates particles and two ON/OFF rubber-seal pneumatic valves that block the working fluid). Double-sided replication employing polydimethylsiloxane (PDMS) was used to fabricate the network, channel, and chamber. Particles were blocked by deformation of the Vs diaphragm, and then accumulated in the curved microfluidic channel. The working fluid was discharged via operation of the two ON/OFF valves. After concentration, particles were released to an outlet port. The Vs pressure required to block solid particles varying in diameter was determined based on the height of the curved microchannel and a finite element method (FEM) simulation of Vs diaphragm displacement. Our method was verified according to the temporal response of the fluid flow rate controlled by the pneumatic valves. Furthermore, all particles with various diameters were successfully blocked, accumulated, and released. The operating pressure, time required for concentration, and concentration ratio were dependent on the particle diameter. The estimated concentration percentage of 24.9 µm diameter polystyrene particles was about 3.82% for 20 min of operation.

Pulsatile flow in stenotic geometries: flow behaviour and stability

2009 ◽  
Vol 622 ◽  
pp. 291-320 ◽  
Author(s):  
M. D. GRIFFITH ◽  
T. LEWEKE ◽  
M. C. THOMPSON ◽  
K. HOURIGAN
Keyword(s):  
Stability Analysis ◽  
Shear Layer ◽  
Linear Stability ◽  
Linear Stability Analysis ◽  
Base Flow ◽  
Arterial Stenosis ◽  
Working Fluid ◽  
Absolute Instability ◽  
Straight Tube ◽  
Instability Modes

Pulsatile inlet flow through a circular tube with an axisymmetric blockage of varying size is studied both numerically and experimentally. The geometry consists of a long, straight tube and a blockage, semicircular in cross-section, serving as a simplified model of an arterial stenosis. The stenosis is characterized by a single parameter, the aim being to highlight fundamental behaviours of constricted pulsatile flows. The Reynolds number is varied between 50 and 700 and the stenosis degree by area between 0.20 and 0.90. Numerically, a spectral element code is used to obtain the axisymmetric base flow fields, while experimentally, results are obtained for a similar set of geometries, using water as the working fluid. For low Reynolds numbers, the flow is characterized by a vortex ring which forms directly downstream of the stenosis, for which the strength and downstream propagation velocity vary with the stenosis degree. Linear stability analysis is performed on the simulated axisymmetric base flows, revealing a range of absolute instability modes. Comparisons are drawn between the numerical linear stability analysis and the observed instability in the experimental flows. The observed flows are less stable than the numerical analysis predicts, with convective shear layer instability present in the experimental flows. Evidence is found of Kelvin–Helmholtz-type shear layer roll-ups; nonetheless, the possibility of the numerically predicted absolute instability modes acting in the experimental flow is left open.

Hydrodynamic Investigations of a Dielectrophoretically Trapped and Agitated Microparticle

2009 ◽  
Author(s):  
Stuart J. Williams ◽  
Steven T. Wereley
Keyword(s):  
Fluid Dynamics ◽  
Particle Image Velocimetry ◽  
Spherical Particle ◽  
Electric Fields ◽  
Particle Image ◽  
Suspended Particle ◽  
Microfluidic Channel ◽  
Induced Polarization ◽  
Image Velocimetry ◽  
Complete Investigation

Understanding the fluid dynamics of a particle in suspension is important for a complete investigation of many hydrodynamic phenomena, including microfluidic models. Dielectrophoresis (DEP) is a technique that can translate and trap particles through induced polarization when in the presence of non-uniform electric fields. Here, DEP has been used to capture and suspend a single 10.1 μm diameter spherical particle in a microfluidic channel. Procedures and results for controlled, oscillatory dielectrophoretic agitation of the suspended particle are shown. Hydrodynamic investigations are discussed including the incorporation of micron-resolution particle image velocimetry (μPIV).

scholarly journals Electrode_configuration_DNA_Sensitivity_Biomicrofluidics

2019 ◽  
Author(s):  
Sagnik Basuray
Keyword(s):  
High Frequency ◽  
Signal To Noise Ratio ◽  
Microfluidic Channel ◽  
Convective Transport ◽  
Electrical Impedance Spectroscopy ◽  
Detection Sensitivity ◽  
High Signal ◽  
Diffusion Dynamics ◽  
Interdigitated Microelectrode ◽  
Carbon Based

Electrical impedance spectroscopy (EIS) sensors through rapid and cost-effectiveoften suffer from poor sensitivity. EIS sensors modified with carbon-basedtransducers show a higher conductance, thereby increasing the sensitivity of the sensor towards biomolecules like DNA. However, the EIS spectra are compromised by the parasitic capacitance of the electric double layer (EDL). Here, a new shear-enhanced, flow-through nonporous, non-planar interdigitated microelectrode sensor has been fabricated that shifts the EDL capacitor to high frequencies. Enhanced convective transport in this sensor disrupts the diffusion dynamics of the EDL, shifting its EIS spectra to high frequency. Concomitantly, the DNA detection signal shifts to high frequency, making the sensor very sensitive, rapid with a high signal to noise ratio. The device consists of a microfluidic channel sandwiched between two sets of top and bottom interdigitated microelectrodes. One of the sets of microelectrodes is packed with carbon-based transducer material like carboxylated single-walled carbon nanotube (SWCNT). Multiple parametric studies of three different electrode configurations of the sensor along with different carbon-based transducer materials are undertaken to understand the fundamental physics and electrochemistry. Sensors packed with SWCNT show femtomolar detection sensitivity from all the different electrode configurations, for a short target-DNA. A 20-fold jump in the signal is noticed from the unique working electrode configuration in contrast to the other electrode configurations. This demonstrates the potential of the sensor for a significant increase in the sensitivity of the detection of DNA and other biomolecules.

Deformation of Nitrogen Bubbles in DC Electric Fields

2006 ◽  
Author(s):  
Feng Chen ◽  
Yao Peng ◽  
Yaozu Song ◽  
Min Chen
Keyword(s):  
Aspect Ratio ◽  
Electric Field ◽  
Electric Fields ◽  
Transformer Oil ◽  
Working Fluid ◽  
Direction Parallel ◽  
Electric Field Magnitude ◽  
Field Magnitude ◽  
Nitrogen Bubbles ◽  
Dc Electric Fields

The deformation of nitrogen bubbles in transformer oil with various DC electric fields was studied experimentally and theoretically. The bubble deformation was visualized by a high-speed digital camera. The major axis of the bubble was elongated along the direction parallel to the applied electric field, with the elongation increasing as the electric field magnitude increased. The electrical Weber number (We) was used to correlate the electric field magnitude and the electric permittivity of the working fluid to the bubble aspect ratio (AR). The experimental results indicate that the bubble aspect ratio increases with increasing We. The total electrical stresses were calculated on an actual bubble shape including the electrostriction stresses.

scholarly journals Dipolophoresis and Travelling-Wave Dipolophoresis of Metal Microparticles

Micromachines ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 259
Author(s):  
Jose Eladio Flores-Mena ◽  
Pablo García-Sánchez ◽  
Antonio Ramos
Keyword(s):  
Electric Fields ◽  
Particle Motion ◽  
Numerical Solutions ◽  
Particle Surface ◽  
Travelling Wave ◽  
Aqueous Electrolytes ◽  
Small Particles ◽  
Ac Electric Fields ◽  
Induced Charge ◽  
Analytical Expressions

We study theoretically and numerically the electrokinetic behavior of metal microparticles immersed in aqueous electrolytes. We consider small particles subjected to non-homogeneous ac electric fields and we describe their motion as arising from the combination of electrical forces (dielectrophoresis) and the electroosmotic flows on the particle surface (induced-charge electrophoresis). The net particle motion is known as dipolophoresis. We also study the particle motion induced by travelling electric fields. We find analytical expressions for the dielectrophoresis and induced-charge electrophoresis of metal spheres and we compare them with numerical solutions. This validates our numerical method, which we also use to study the dipolophoresis of metal cylinders.

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