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

Wang, Jingyu; Wei, Ming-Tzo; Cohen, Joel A.; Ou-Yang, H. Daniel

doi:10.1002/elps.201200614

Cited by 9 publications

(12 citation statements)

References 33 publications

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“…The amplitudes of the high-frequency terms (higher than Ω B ) are small due to water damping [32]. Thus, we can ignore the higher frequency term and only consider the first three terms (in boldface in Equation 2).…”

Section: Phoretic Force Spectroscopymentioning

confidence: 99%

Frequency Response of Induced-Charge Electrophoretic Metallic Janus Particles

Shen

Jiang

et al. 2020

Micromachines

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The ability to manipulate and control active microparticles is essential for designing microrobots for applications. This paper describes the use of electric and magnetic fields to control the direction and speed of induced-charge electrophoresis (ICEP) driven metallic Janus microrobots. A direct current (DC) magnetic field applied in the direction perpendicular to the electric field maintains the linear movement of particles in a 2D plane. Phoretic force spectroscopy (PFS), a phase-sensitive detection method to detect the motions of phoretic particles, is used to characterize the frequency-dependent phoretic mobility and drag coefficient of the phoretic force. When the electric field is scanned over a frequency range of 1 kHz–1 MHz, the Janus particles exhibit an ICEP direction reversal at a crossover frequency at ~30 kH., Below this crossover frequency, the particle moves in a direction towards the dielectric side of the particle, and above this frequency, the particle moves towards the metallic side. The ICEP phoretic drag coefficient measured by PFS is found to be similar to that of the Stokes drag. Further investigation is required to study microscopic interpretations of the frequency at which ICEP mobility switched signs and the reason why the magnitudes of the forward and reversed modes of ICEP are so different.

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Section: Phoretic Force Spectroscopymentioning

confidence: 99%

Frequency Response of Induced-Charge Electrophoretic Metallic Janus Particles

Shen

Jiang

et al. 2020

Micromachines

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“…In our experiments, particle sizes were larger than the Debye length (k D ), which was calculated to be k D $ 200 nm in de-ionized water in equilibrium with atmospheric CO 2 . 25 For micron and submicron particles that satisfy r ) k D , namely, the particle size is much larger than the Debye length, a-relaxation time is…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…The particle was positioned near the center between the electrode tips to minimize the influence from AC electroosmosis, which, the same as DEP, is also E 2 dependent. 25 We use the same design principals described in details before 3,4 to determine the DEP crossover frequencies. Here, a 3 Vpp AC at radial frequencies was applied across the pair of electrodes, creating an electric field gradient.…”

Section: Optical Tweezers-based Force Sensormentioning

confidence: 99%

“…Since the particle was located far from the electrodes, the effect due to AC electroosmosis was negligible, and the measured force was dominated by the DEP force. 25 The AM frequency was two orders of magnitude lower than the DEP frequency to avoid crosstalk with the DEP frequency and to allow the particle to be responsive to the modulated DEP force such that the particle motion is detectable. We identify the DEP crossover frequency to be the frequency at which the magnitude of the particle motion approaches zero and the phase of the particle motion switches by 180 .…”

Section: Optical Tweezers-based Force Sensormentioning

confidence: 99%

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Low-frequency dielectrophoretic response of a single particle in aqueous suspensions

2016

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We use optical tweezers-based dielectrophoresis (DEP) force spectroscopy to investigate the roles of the electrical double layer in the AC dielectric response of an individual colloidal particle in an aqueous medium. Specifically, we measure the DEP crossover frequency as a function of particles size, medium viscosity, and temperature. Experimental results were compared to low frequency relaxation mechanisms predicted by Schwarz, demonstrating the dielectrophoretic responses in the frequency range between 10 kHz and 1 MHz were dominated by counterion diffusion within the electric double layer. V C 2016 AIP Publishing LLC.

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“…In most electrokinetics studies [103,104], ACEO and DEP often complicate each other. The presence of surface irregularities, or protruding electrode surface like surface relief in this case, often produces non-uniform field that…”

Section: Theoretical Basismentioning

confidence: 99%

Guided colloidal crystallization

Ng¹

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The expanse of single crystallinity in two-dimensional colloidal crystal is limited by the difficulty to control its nucleation, leading to multi-domain growth, empty bands and voids. Using a straight nucleation line, this thesis demonstrates techniques to engineer preferential nucleation and in-plane growth of monolayer colloidal crystal in both convective-induced self-assembly and electric field assisted self-assembly. In convective driven self-assembly, a straight nucleation line is achieved by pinning the air-liquid-solid contact line along the edge of a straight surface relief. With evaporation, convective driven particle flux to the edge of surface relief enables the formation of a perfect nucleation seed, followed by subsequent in-plane growth to produce large area single domain of monolayer colloidal crystal. A model describing the criteria for successful meniscus pinning near the surface relief is proposed, with consideration of surface relief height. A similar surface relief with conductive coating is used in electric field assisted self-assembly, to attract particle accumulation and ordering by both Dielectrophoresis (DEP) and AC Electroosmosis (ACEO) forces, respectively. Near the surface relief of an electrode, preferential particle adsorption and nucleation of colloidal arrays are achieved, giving rise to in-plane growth of monolayer colloidal crystal. In addition, by analysing DEP and ACEO using finite-element method, DEP is found to be crucial in the nucleation of colloidal crystal near the surface relief, preceding the growth driven by ACEO forces. Lastly, both convective-induced selfassembly and electric field assisted self-assembly using straight surface reliefs are compared in terms of crystal quality, processing advantages and limitations.

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

Cited by 9 publications

References 33 publications

Frequency Response of Induced-Charge Electrophoretic Metallic Janus Particles

Frequency Response of Induced-Charge Electrophoretic Metallic Janus Particles

Low-frequency dielectrophoretic response of a single particle in aqueous suspensions

Guided colloidal crystallization

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