Colloidal Crosstalk: Brownian Diffusion of Hydrodynamically Coupled Colloids

Except at dilute concentrations, the Stokes-Einstein Equation inadequately describes the thermal motion of colloids, due to hydrodynamic interactions between nearby particles. Using single-particle tracking, the rotational and translational motion of hydrodynamically interacting colloids is observed, and deviations from the Stokes-Einstein Equation are readily apparent. The thermal motion of nearby colloids is found to couple in a non-additive fashion, with increasing degrees of non-linearity as particle separation decreases. Similar coupling is observed for colloids near surfaces.