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Brownian motion near a partial-slip boundary: A local probe of the no-slip condition

Lauga, Eric and Squires, Todd M. (2005) Brownian motion near a partial-slip boundary: A local probe of the no-slip condition. Physics of Fluids, 17 (10). Art. no. 103102. ISSN 1070-6631. doi:10.1063/1.2083748.

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Motivated by experimental evidence of violations of the no-slip boundary condition for liquid flow in micrometer-scale geometries, we propose a simple, complementary experimental technique that has certain advantages over previous studies. Instead of relying on externally induced flow or probe motion, we suggest that colloidal diffusivity near solid surfaces contains signatures of the degree of fluid slip exhibited on those surfaces. To investigate, we calculate the image system for point forces (Stokeslets) oriented perpendicular and parallel to a surface with a finite slip length, analogous to Blake's solution for a Stokeslet near a no-slip wall. Notably, the image system for the point source and perpendicular Stokeslet contain the same singularities as Blake's solution; however, each is distributed along a line with a magnitude that decays exponentially over the slip length. The image system for the parallel Stokeslet involves a larger set of fundamental singularities, whose magnitude does not decay exponentially from the surface. Using these image systems, we determine the wall-induced correction to the diffusivity of a small spherical particle located "far" from the wall. We also calculate the coupled diffusivities between multiple particles near a partially slipping wall. Because, in general, the diffusivity depends on "local" wall conditions, patterned surfaces would allow differential measurements to be obtained within a single experimental cell, eliminating potential cell-to-cell variability encountered in previous experiments. In addition to motivating the proposed experiments, our solutions for point forces and sources near a partial-slip wall will be useful for boundary integral calculations in slip systems.

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Additional Information:©2005 American Institute of Physics (Received 8 June 2005; accepted 18 August 2005; published online 19 October 2005) We thank L. Bocquet and H. Chen for useful discussions. E.L. gratefully acknowledges support of the Office of Naval Research (Grant No. N00014-03-1-0376)nd the Harvard MRSEC. T.M.S. gratefully acknowledges the support of the Lee A. Dubridge Prize Postdoctoral Fellowship and the NSF Mathematical Sciences Postdoctoral Fellowship.
Subject Keywords:Brownian motion; slip flow; colloids; two-phase flow; diffusion; boundary integral equations
Issue or Number:10
Record Number:CaltechAUTHORS:LAUpof05
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1309
Deposited By: Archive Administrator
Deposited On:09 Jan 2006
Last Modified:08 Nov 2021 19:09

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