Title: Correlations in Suspensions Confined between Viscoelastic Surfaces: Noncontact Microrheology
Author: Chen Bar-Haim
We study analytically the velocity cross-correlations in a viscous fluid confined inside a slit between two viscoelastic media, and their effect on the correlated motions of particles suspended in the fluid. The compliance of the confining medium gives rise to a long-ranged correlation, decaying as 1/ with inter-particle distance , on top of the 1/2 correlations known for rigid slits . We show how this extra correlation may be used to extract the viscoelastic properties of the medium through noncontact two-point microrheology, i.e., without embedding tracer particles in the medium itself. We discuss the remarkable robustness of such a potential technique against details of the confining slit, and its statistical advantages over standard two-point microrheology.