We study the correlated motions of colloidal particles in a quasi-2D system (Human Serum Albumin (HSA) protein molecules at an air-water interface) for different surface viscosities ηs. We observe a transition in the behavior of the correlated motion, from 2-D interface dominated at high ηs to bulk fluid-dependent at low ηs. The correlated motions can be scaled onto a master curve which captures the features of this transition. This master curve also characterizes the spatial dependence of the flow field of a viscous interface in response to a force. From the flow field and the correlated particle motions, we calculate a two-particle MSD (mean square displacement) for direct comparison with rheological measurements.
@article{arxiv.cond-mat/0604262,
title = {Two-Particle Microrheology of quasi-2D Viscous Systems},
author = {V. Prasad and S. A. Koehler and Eric R. Weeks},
journal= {arXiv preprint arXiv:cond-mat/0604262},
year = {2007}
}