Induced-charge electroosmotic trapping of particles

Abstract

Position-controllable trapping of particles on the surface of a bipolar metal strip by induced-charge electroosmotic (ICEO) flow is presented herein. We demonstrate a nonlinear ICEO slip profile on the electrode surface accounting for stable particle trapping behaviors above the double-layer relaxation frequency, while no trapping occurs in the DC limit as a result of a strong upward fluidic drag induced by a linear ICEO slip profile. By extending an AC-flow field effect transistor from the DC limit to the AC field, we reveal that fixed-potential ICEO exceeding RC charging frequency can adjust the particle trapping position flexibly by generating controllable symmetry breaking in a vortex flow pattern. Our results open up new opportunities to manipulate microscopic objects in modern microfluidic systems by using ICEO.

On utilizing alternating current-flow field effect transistor for flexibly manipulating particles in microfluidics and nanofluidics

“…Lots of particles are quite uniformly distributed within a large circular region on top of the blocking surface, in that a linear ICEO slip profile within thin layer approximation induces a strong upward fluidic drag. 48 With frequency to x ¼ 3 k D , the ICEO flow velocity decreases due to a charge relaxation process, giving it a chance for the downward buoyancy force to effectively counteract the upward ICEO flow component, hence more stable particle trapping takes place on the gate electrode with the maximum concentration attaining 139 ( Fig. 3(c)) as compared to a much lower concentrating performance at lower frequencies (Figs.…”

“…In the meantime, the aggregation pattern of nano-colloid widens slightly, since the transverse ICEO convective flow acting as the main driving force for particle trapping decays and exhibits a nonlinear slip profile above the electrode surface. 48 On increasing frequency to x ¼ 5 k D , the span of collection pattern further extends, while the trapping performance enhances with a maximum concentration reaching to 290, due to a complicated interplay among the ICEO flow field of an elaborate nonlinear slip profile, downward buoyancy force and thermal diffusion ( Fig. 3(d)).…”

A microscopic physical description of electrothermal‐induced flow for control of ion current transport in microfluidics interfacing nanofluidics

“…Electrohydrodynamics (EHDs) has been acquiring unprecedentedly increasing attention from the microfluidic community since the last two decades [4][5][6]. Traditional DC electroosmosis (EO) [7,8], electrowetting on dielectrics [9], injection EHD [10], conduction EHD [11], traveling-wave induction EHD [12][13][14][15], inducedcharge electroosmosis (ICEO) [16][17][18][19][20][21][22][23][24], dielectrophoresis (DEP) [25][26][27][28][29][30], electrothermal (ET) induced flow [31][32][33][34][35][36][37], and electroconvective instability (EI) [38][39][40] near a permselective membrane are all authoritative methodologies where electric fields are employed to actuate liquid solutions in miniaturization systems.…”

Scaled particle focusing in a microfluidic device with asymmetric electrodes utilizing induced-charge electroosmosis

“…Meanwhile, electrokinetic techniques are increasingly employed in manipulation of particles, because of the benefits of simple structures, non-invasiveness and real-time detection. Compared with ACEO method where all electrodes are subject to voltage signals, 17,18 the ICEO particle focusing on multiple metal strips, which was named floating electrode by Leinweber et al [19][20][21][22] for being free from external circuit, provides a significant convenience for device integration. It has been well documented that DEP can be used for particle focusing.…”