Induced-charge electro-osmosis

By T. Squires, Martin Z. Bazant. Journal of Fluid Mechanics, 2003

641 citations recorded by the source corpus.

We describe the general phenomenon of ‘induced-charge electro-osmosis’ (ICEO) – the nonlinear electro-osmotic slip that occurs when an applied field acts on the ionic charge it induces around a polarizable surface. Motivated by a simple physical picture, we calculate ICEO flows around conducting cylinders in steady (DC), oscillatory (AC), and suddenly applied electric fields. This picture, and these systems, represent perhaps the clearest example of nonlinear electrokinetic phenomena. We complement and verify this physically motivated approach using a matched asymptotic expansion to the electrokinetic equations in the thin-double-layer and low-potential limits. ICEO slip velocities vary as $u_s \,{\propto}\,E_0^2 L$, where $E_0$ is the field strength and $L$ is a geometric length scale, and are set up on a time scale $\tau_c \,{=}\,\lambda_D L/D$, where $\lambda_D$ is the screening length and $D$ is the ionic diffusion constant. We propose and analyse ICEO microfluidic pumps and mixers that operate without moving parts under low applied potentials. Similar flows around metallic colloids with fixed total charge have been described in the Russian literature (largely unnoticed in the West). ICEO flows around conductors with fixed potential, on the other hand, have no colloidal analogue and offer further possibilities for microfluidic applications.

Subfields: Biomedical Engineering, Physical and Theoretical Chemistry

View Paper: https://www.semanticscholar.org/paper/c2185a86279eeeb448f68e94abc8ace1dd10c1d1

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Citations in the corpus

Breaking symmetries in induced-charge electro-osmosis and electrophoresis (2005, methodology): “Here, we consider conductors and dielectrics without any fixed charges, so we have only the bare total charge Q0, which is typically screened to give Q̃0 = 0, although Q̃0 = 0 is possible out of equilibrium in fixedpotential ICEO (Squires & Bazant 2004).”
AN ASYMPTOTIC DERIVATION OF THE THIN-DEBYE-LAYER LIMIT FOR ELECTROKINETIC PHENOMENA (2009, background): “We note that the assumption of small Péclet numbers, so common in prevailing analyses (Squires and Bazant, 2004), is flawed.”
Electrokinetic locomotion due to reaction-induced charge auto-electrophoresis (2010, background): “Squires & Bazant (2006) more generally examined the consequences of broken symmetries for ICEO and ICEP flows.”
Advances in electrokinetics and their applications in micro/nano fluidics (2012, background): “where ed and ef are dielectric constants of dielectric block and electrolyte fluid, respectively, and fd0 is the conventional zeta potential corresponding to natural surface charge density qd0 and is related to qd0 by (Squires and Bazant 2004)”
Induced-charge electrokinetic phenomena (2003, methodology): “The Standard Model has been widely used to model nonlinear electrokinetic phenomena in microfluidic devices, such as ACEO flows around electrode pairs [9,11,12,13] and arrays [10,14,59,61–63], TWEO flows [32,33,72], ICEO flow around metal structures [18,19,20,39,40, 54,55,73] and dielectric corners ”
Towards an understanding of induced-charge electrokinetics at large applied voltages in concentrated solutions. (2009, methodology): “for oscillating momentum boundary layers and vortex shedding in response to AC forcing [16,43].”
Microfluidics: Fluid physics at the nanoliter scale (2005, background): “39 Murtsovkin, 1996; Bazant and Squires, 2004; Squires and Bazant, 2004 .”