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Anisotropic diffusion in confined colloidal dispersions: The evanescent diffusivity

Swan, James W. and Brady, John F. (2011) Anisotropic diffusion in confined colloidal dispersions: The evanescent diffusivity. Journal of Chemical Physics, 135 (1). Art. No. 014701. ISSN 0021-9606.

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We employ an analogy to traditional dynamic light scattering to describe the inhomogeneous and anisotropic diffusion of colloid particles near a solid boundary measured via evanescent wave dynamic light scattering. Following this approach, we generate new expressions for the short-time self- and collective diffusivities of colloidal dispersions with arbitrary volume fraction. We use these expressions in combination with accelerated Stokesian dynamics simulations to calculate the diffusivities in the limit of large and small scattering wave numbers for evanescent penetration depths ranging from four particle radii to one-fifth of a particle radius and volume fractions from 10% to 40%. We show that at high volume fractions, and larger penetration depths, the boundaries have little effect on the dynamics of the suspension parallel to the wall since, to a first approximation, the boundary acts hydrodynamically much as another nearby particle. However, near and normal to the wall, the diffusivity shows a strong dependence on penetration depth for all volume fractions. This is due to the lubrication interactions between the particles and the boundary as the particle moves relative to the wall. These results are novel and comprehensive with respect to the range of penetration depth and volume fraction and provide a complete determination of the effect of hydrodynamic interactions on colloidal diffusion adjacent to a rigid boundary.

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Additional Information:© 2011 American Institute of Physics. Received 13 November 2010; accepted 6 June 2011; published online 1 July 2011.
Subject Keywords:boundary-value problems; colloids; diffusion; light scattering
Issue or Number:1
Classification Code:PACS: 82.70.Dd, 47.57.eb
Record Number:CaltechAUTHORS:20110802-135414917
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:24629
Deposited By: Jason Perez
Deposited On:02 Aug 2011 22:56
Last Modified:03 Oct 2019 02:58

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