(186ay) Directional Locking and Deterministic Separation in Periodic Arrays

We investigate the transport of a suspended, non-Brownian sphere moving through a periodic array of stationary spheres by means of Stokesian Dynamics simulations. We show that in the presence of non-hydrodynamic, short-range interactions the moving particle become locked into periodic trajectories with an average orientation that coincides with one of the lattice directions and is, in general, different from the direction of the driving force. The locking angle depends on the details of the non-hydrodynamic interactions, and could lead to vector separation of different species for certain orientations of the external force. We explicitly show the presence of separation for the case of a mixture of suspended particles with different roughness.