(518a) Hydrodynamically Interacting Particles Confined By a Spherical Cavity Via Dynamic Simulations

Authors: 
Aponte-Rivera, C., Cornell University
Zia, R., Cornell University

We study the diffusion in and rheology of hydrodynamically interacting colloids confined by a spherical cavity via dynamic simulation, as a model of intracellular and other confined biophysical transport. Previous attempts to model such behavior have been limited primarily to a single particle inside a spherical cavity. Although attempts have been made to extend such models to more than one confined particle, none has yet successfully accounted for the effects of hydrodynamics, owing to the difficulties of modeling many-body long-ranged interactions. In some such studies, attempts have been made to circumvent this difficulty by modeling all particle interactions as pairwise additive, and accounting only for leading-order far-field interactions (neglecting near-field lubrication interactions entirely). In the present study, we utilize a Stokesian- dynamics like approach, implementing our newly derived mobility functions to fully account for all many-body far-field interactions between the particles themselves, and between particles and the enclosing cavity. Together with the appropriate near-field resistance functions, these form a complete model for simulation of the motion of an arbitrary number of particles enclosed by a cavity of arbitrary size relative to the particles. Here we report the short- and long- time self-diffusion at equilibrium, with a focus on the dependence of the former on particle positions relative to the cavity, and of both on volume fraction and size ratio. Comparison to recent experimental results is discussed.