scholarly journals Asymmetric rectified electric fields generate flows that can dominate induced-charge electrokinetics

2020 ◽  
Vol 5 (1) ◽  
Author(s):  
S. M. H. Hashemi Amrei ◽  
Gregory H. Miller ◽  
William D. Ristenpart
Keyword(s):  
Electric Fields ◽  
Induced Charge

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

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.

The effect of Brownian motion on the stability of sedimenting suspensions of polarizable rods in an electric field

2009 ◽  
Vol 624 ◽  
pp. 361-388 ◽  
Author(s):  
BRENDAN D. HOFFMAN ◽  
ERIC S. G. SHAQFEH
Keyword(s):  
Brownian Motion ◽  
Electric Fields ◽  
Brownian Dynamics ◽  
Mean Field ◽  
Thermal Motion ◽  
Particle Orientation ◽  
Induced Charge ◽  
The Stability ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations

We examine the collective dynamics of polarizable, Brownian, sedimenting rods of high aspect ratio. Previous work of Koch and Shaqfeh (J. Fluids Mech., vol. 209, 1989 pp. 521–542) has shown that in the absence of Brownian motion, sedimenting suspensions of rods are unstable to concentration fluctuations and form dense streamers via interparticle hydrodynamic interactions. Recently, Saintillan, Shaqfeh & Darve (Phys. Fluids, vol. 18 (121701), 2006b p. 1) demonstrated that electric fields can act to stabilize these non-Brownian suspensions of polarizable rods through induced-charge electrokinetic rotation, which forces particle alignment. In this paper, we employ a mean-field linear stability analysis as well as Brownian dynamics simulations to study the effect of thermal motion on the onset of instability. We find that in the absence of electric fields, Brownian motion consistently suppresses instability formation through randomization of particle orientation. However, when electric fields are applied, thermal motion can act to induce instability by counteracting the stabilizing effect of induced-charge orientation.

Induced-charge electro-osmotic flow around cylinders with various orientations

2016 ◽  
Vol 231 (21) ◽  
pp. 4057-4066 ◽  
Author(s):  
Cetin Canpolat
Keyword(s):  
Electric Fields ◽  
Double Layers ◽  
Cylinder Surface ◽  
Osmotic Flow ◽  
Ac Electric Fields ◽  
Velocity Magnitude ◽  
Electro Osmosis ◽  
Microparticle Image Velocimetry ◽  
Induced Charge ◽  
Electro Osmotic Flow

Induced-charge electro-osmosis around multiple gold-coated stainless steel rods under various AC electric fields is investigated using the techniques of microparticle image velocimetry and numerical simulation. In this study, the results of interactions between induced electric double layers of two identical conductive cylinders on surrounding fluid are presented. The induced-charge electro-osmosis flow around multiple rods in touch and with one cylinder diameter gap reveals quadrupolar flow structures with four vortices. The induced-charge electro-osmotic flow structure and velocity magnitude also depend on the cylinder geometry and orientation. It is seen that four small vortices develop in the close region of cylinder surface for multiple rods with gap, while the other four large vortices are surrounding them. The distributions of vorticity patterns also strongly depend on cylinder orientation in the close region of cylinder surface.

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.

Electrokinetic locomotion due to reaction-induced charge auto-electrophoresis

2011 ◽  
Vol 680 ◽  
pp. 31-66 ◽  
Author(s):  
JEFFREY L. MORAN ◽  
JONATHAN D. POSNER
Keyword(s):  
Electric Fields ◽  
Reaction Rate ◽  
Surface Reaction ◽  
Stokes Equations ◽  
Electrochemical Reactions ◽  
Scaling Analysis ◽  
Governing Equations ◽  
Induced Charge ◽  
Scaling Analyses ◽  
Strong Agreement

Mitchell originally proposed that an asymmetric ion flux across an organism's membrane could generate electric fields that drive locomotion. Although this locomotion mechanism was later rejected for some species of bacteria, engineered Janus particles have been realized that can swim due to ion fluxes generated by asymmetric electrochemical reactions. Here we present governing equations, scaling analyses and numerical simulations that describe the motion of bimetallic rod-shaped motors in hydrogen peroxide solutions due to reaction-induced charge auto-electrophoresis. The coupled Poisson–Nernst–Planck–Stokes equations are numerically solved using Frumkin-corrected Butler–Volmer equations to represent electrochemical reactions at the rod surface. Our simulations show strong agreement with the scaling analysis and experiments. The analysis shows that electrokinetic locomotion results from electro-osmotic fluid slip around the nanomotor surface. The electroviscous flow is driven by electrical body forces which are generated from a coupling of a reaction-induced dipolar charge density distribution and the electric field it creates. The magnitude of the electroviscous velocity increases quadratically with the surface reaction rate for an uncharged motor, and linearly when the motor supports a finite surface charge.

Induced-Charge Electroosmosis Around Touching Metal Rods

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Cetin Canpolat ◽  
Mingkan Zhang ◽  
William Rosen ◽  
Shizhi Qian ◽  
Ali Beskok
Keyword(s):  
Electric Fields ◽  
Radial Distance ◽  
Flow Structures ◽  
Weakly Nonlinear ◽  
Ac Electric Fields ◽  
Velocity Magnitude ◽  
Micro Piv ◽  
Image Velocimetry ◽  
Microparticle Image Velocimetry ◽  
Induced Charge

Induced-charge electroosmosis (ICEO) around multiple gold-coated stainless steel rods under different ac electric fields is analyzed using microparticle image velocimetry (micro-PIV) and numerical simulations. In the present investigation, the induced electric double layer (EDL) is in weakly nonlinear limit. The ICEO flow around multiple touching rods exhibits geometry dependent quadrupolar flow structures with four vortices. The velocity magnitude is proportional to the square of the electric field. The ICEO flow velocity also depends on the cylinder orientation. The velocity increases with increased radial distance from the rod’s surface, attains a maximum, and then decays to zero. Experimental and numerical velocity distributions have the same trend beyond 0.2 mm of the rod’s surface.

scholarly journals Multifrequency Induced-Charge Electroosmosis

Micromachines ◽  
2019 ◽  
Vol 10 (7) ◽  
pp. 447 ◽  
Author(s):  
Kai Du ◽  
Jingni Song ◽  
Weiyu Liu ◽  
Ye Tao ◽  
Yukun Ren
Keyword(s):  
Electric Fields ◽  
Physical Phenomenon ◽  
Electrode Arrays ◽  
Fluidic Channel ◽  
Particle Tracing ◽  
Convective Mixing ◽  
Ac Electric Fields ◽  
Electroosmotic Pump ◽  
Induced Charge ◽  
On Chip

We present herein a unique concept of multifrequency induced-charge electroosmosis (MICEO) actuated directly on driving electrode arrays, for highly-efficient simultaneous transport and convective mixing of fluidic samples in microscale ducts. MICEO delicately combines transversal AC electroosmotic vortex flow, and axial traveling-wave electroosmotic pump motion under external dual-Fourier-mode AC electric fields. The synthetic flow field associated with MICEO is mathematically analyzed under thin layer limit, and the particle tracing experiment with a special powering technique validates the effectiveness of this physical phenomenon. Meanwhile, the simulation results with a full-scale 3D computation model demonstrate its robust dual-functionality in inducing fully-automated analyte transport and chaotic stirring in a straight fluidic channel embedding double-sided quarter-phase discrete electrode arrays. Our physical demonstration with multifrequency signal control on nonlinear electroosmosis provides invaluable references for innovative designs of multifunctional on-chip analytical platforms in modern microfluidic systems.

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