dorsal/arxiv
View SchemaInduced-Charge Electro-Osmosis
| Authors | Todd M. Squires, Martin Z. Bazant |
|---|---|
| Categories | |
| ArXiv ID | physics/0304090 |
| URL | https://arxiv.org/abs/physics/0304090 |
| DOI | 10.1017/S0022112004009309 |
| Journal | J. Fluid Mech. 509, 217-252 (2004) |
Abstract
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 {\sl 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 like $u_s \propto E_0^2 L$, 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 analyze 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 analog and offer further possibilities for microfluidic applications.
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"abstract": "We describe the general phenomenon of `induced-charge electro-osmosis\u0027 (ICEO)\n-- the nonlinear electro-osmotic slip that occurs when an applied field acts on\nthe ionic charge it {\\sl induces} around a polarizable surface. Motivated by a\nsimple physical picture, we calculate ICEO flows around conducting cylinders in\nsteady (DC), oscillatory (AC), and suddenly-applied electric fields. This\npicture, and these systems, represent perhaps the clearest example of nonlinear\nelectrokinetic phenomena. We complement and verify this physically-motivated\napproach using a matched asymptotic expansion to the electrokinetic equations\nin the thin double-layer and low potential limits. ICEO slip velocities vary\nlike $u_s \\propto E_0^2 L$, where $E_0$ is the field strength and $L$ is a\ngeometric length scale, and are set up on a time scale $\\tau_c = \\lambda_D\nL/D$, where $\\lambda_D$ is the screening length and $D$ is the ionic diffusion\nconstant. We propose and analyze ICEO microfluidic pumps and mixers that\noperate without moving parts under low applied potentials. Similar flows around\nmetallic colloids with fixed total charge have been described in the Russian\nliterature (largely unnoticed in the West). ICEO flows around conductors with\nfixed potential, on the other hand, have no colloidal analog and offer further\npossibilities for microfluidic applications.",
"arxiv_id": "physics/0304090",
"authors": [
"Todd M. Squires",
"Martin Z. Bazant"
],
"categories": [
"physics.flu-dyn",
"cond-mat.soft",
"physics.chem-ph"
],
"doi": "10.1017/S0022112004009309",
"journal_ref": "J. Fluid Mech. 509, 217-252 (2004)",
"title": "Induced-Charge Electro-Osmosis",
"url": "https://arxiv.org/abs/physics/0304090"
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