ac electroosmotic pumping induced by noncontact external electrodes

Wang, Shau‐Chun; Chen, Hsiao-Ping

doi:10.1063/1.2784137

Cited by 9 publications

(7 citation statements)

References 14 publications

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“…Figure shows a maximum | v x | at ∼117 kHz, measured at the point

(x \approx 10 μ normalm, z \approx 3 μ normalm)

, a location close to the electrode tip. Our frequency dependence of the ACEO flow velocity is consistent with the data of Wang et al (Shau‐Chun Wang and Hsiao‐Ping Chen, personal communication) who found a velocity maximum at ∼120 kHz obtained by measuring the velocity of a moving front of dye molecules in a particle‐free ∼0.1 mM monovalent salt solution driven by an ACEO micropump. Green et al conducted ACEO PIV experiments with 557 latex tracer particles in three KCl solutions and found, for the solution of lowest conductivity (∼20 μS/cm), the maximum velocity near the electrode surface at ∼100–200 Hz.…”

Section: Resultssupporting

confidence: 91%

Mapping alternating current electroosmotic flow at the dielectrophoresis crossover frequency of a colloidal probe

et al. 2013

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AC electroosmotic (ACEO) flow above the gap between coplanar electrodes is mapped by the measurement of Stokes forces on an optically trapped polystyrene colloidal particle. E²-dependent forces on the probe particle are selected by amplitude modulation (AM) of the ACEO electric field (E) and lock-in detection at twice the AM frequency. E²-dependent DEP of the probe is eliminated by driving the ACEO at the probe's DEP crossover frequency. The location-independent DEP crossover frequency is determined, in a separate experiment, as the limiting frequency of zero horizontal force as the probe is moved toward the midpoint between the electrodes. The ACEO velocity field, uncoupled from probe DEP effects, was mapped in the region 1-9 μm above a 28 μm gap between the electrodes. By use of variously sized probes, each at its DEP crossover frequency, the frequency dependence of the ACEO flow was determined at a point 3 μm above the electrode gap and 4 μm from an electrode tip. At this location the ACEO flow was maximal at ∼117 kHz for a low salt solution. This optical trapping method, by eliminating DEP forces on the probe, provides unambiguous mapping of the ACEO velocity field.

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“…Figure shows a maximum | v x | at ∼117 kHz, measured at the point

(x \approx 10 μ normalm, z \approx 3 μ normalm)

Section: Resultssupporting

confidence: 91%

Mapping alternating current electroosmotic flow at the dielectrophoresis crossover frequency of a colloidal probe

et al. 2013

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“…Particles with sizes of 200 nm (fluorescent, Molecular Probes) and 1 μm (Polystyrene spheres; Fluka Chemica) were suspended in deionized (DI) water to track fluid motion. A frequency range from 100 Hz to 1 kHz was determined to be optimal for observing particle motion in the DI water suspension []. The particle movement was observed using Nikon LV100 microscope through the top of PDMS microchamber.…”

Section: Resultsmentioning

confidence: 99%

Bi‐directional flow induced by an AC electroosmotic micropump with DC voltage bias

Islam¹,

Reyna²

2012

Electrophoresis

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This paper discusses the principle of biased alternating current electroosmosis (ACEO) and its application to move the bulk fluid in a microchannel, as an alternative to mechanical pumping methods. Previous EO-driven flow research has looked at the effect of electrode asymmetry and transverse traveling wave forms on the performance of electroosmotic pumps. This paper presents an analysis that was conducted to assess the effect of combining an AC signal with a DC (direct current) bias when generating the electric field needed to impart electroosmosis (EO) within a microchannel. The results presented here are numerical and experimental. The numerical results were generated through simulations performed using COMSOL 3.5a. Currently available theoretical models for EO flows were embedded in the software and solved numerically to evaluate the effects of channel geometry, frequency of excitation, electrode array geometry, and AC signal with a DC bias on the flow imparted on an electrically conducting fluid. Simulations of the ACEO flow driven by a constant magnitude of AC voltage over symmetric electrodes did not indicate relevant net flows. However, superimposing a DC signal over the AC signal on the same symmetric electrode array leads to a noticeable net forward flow. Moreover, changing the polarity of electrical signal creates a bi-directional flow on symmetrical electrode array. Experimental flow measurements were performed on several electrode array configurations. The mismatch between the numerical and experimental results revealed the limitations of the currently available models for the biased EO. However, they confirm that using a symmetric electrode array excited by an AC signal with a DC bias leads to a significant improvement in flow rates in comparison to the flow rates obtained in an asymmetric electrode array configuration excited just with an AC signal.

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“…5A), in contrast to an hour-long purely diffusive mixing. The same group [85] later used a similar device to demonstrate a high-throughput AC electroosmotic pump based on the field induced-polarization on the entire channel surface (Fig. 5B).…”

Section: Microfluidic Mixing and Pumpingmentioning

confidence: 99%

Review of nonlinear electrokinetic flows in insulator‐based dielectrophoresis: From induced charge to Joule heating effects

Xuan

2021

Electrophoresis

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Insulator‐based dielectrophoresis (iDEP) has been increasingly used for particle manipulation in various microfluidic applications. It exploits insulating structures to constrict and/or curve electric field lines to generate field gradients for particle dielectrophoresis. However, the presence of these insulators, especially those with sharp edges, causes two nonlinear electrokinetic flows, which, if sufficiently strong, may disturb the otherwise linear electrokinetic motion of particles and affect the iDEP performance. One is induced charge electroosmotic (ICEO) flow because of the polarization of the insulators, and the other is electrothermal flow because of the amplified Joule heating in the fluid around the insulators. Both flows vary nonlinearly with the applied electric field (either DC or AC) and exhibit in the form of fluid vortices, which have been utilized to promote some applications while being suppressed in others. The effectiveness of iDEP benefits from a comprehensive understanding of the nonlinear electrokinetic flows, which is complicated by the involvement of the entire iDEP device into electric polarization and thermal diffusion. This article is aimed to review the works on both the fundamentals and applications of ICEO and electrothermal flows in iDEP microdevices. A personal perspective of some future research directions in the field is also given.

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ac electroosmotic pumping induced by noncontact external electrodes

Cited by 9 publications

References 14 publications

Mapping alternating current electroosmotic flow at the dielectrophoresis crossover frequency of a colloidal probe

Mapping alternating current electroosmotic flow at the dielectrophoresis crossover frequency of a colloidal probe

Bi‐directional flow induced by an AC electroosmotic micropump with DC voltage bias

Review of nonlinear electrokinetic flows in insulator‐based dielectrophoresis: From induced charge to Joule heating effects

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