  Motivated by experimental evidence of violations of the no-slip boundary
condition for liquid flow in micron-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.
