Hydrodynamic interactions between colloidal particles in a planar pore.

The correlation between the motion of pairs of colloidal particles confined in a planar pore is measured using optical microscopy. The systems studied here are aqueous suspensions of polystyrene spheres of diameter 1.9 μm, interacting as effective hard spheres, confined between two parallel planar plates separated by 2.9 μm. The lateral motion, along the plane parallel to the plates, of the particles is recorded with a time resolution of 30 frames s(-1). From the short-time motion, the hydrodynamic diffusion coefficients are determined as functions of the interparticle distance for various particle concentrations. At low concentrations, when the static correlation between particles is also low, the diffusion coefficients exhibit some symmetry, and at higher concentrations they are modulated by the structure of static correlation.