We describe direct imaging measurements of the collective and relative diffusion of two colloidal spheres near a flat plate. The bounding surface modifies the spheres' dynamics, even at separations of tens of radii. This behavior is captured by a stokeslet analysis of fluid flow driven by the spheres' and wall's no-slip boundary conditions. In particular, this analysis reveals surprising asymmetry in the normal modes for pair diffusion near a flat surface.
@article{arxiv.cond-mat/0003314,
title = {Hydrodynamic Coupling of Two Brownian Spheres to a Planar Surface},
author = {Eric R. Dufresne and Todd M. Squires and Michael P. Brenner and David G. Grier},
journal= {arXiv preprint arXiv:cond-mat/0003314},
year = {2009}
}