Microfabrication of Anisotropic Media for Particle Separation Devices

We study the effect of anisotropic geometry on the diffusion of suspended particles in periodic array of rectangular obstacles. We directly measure the Brownian motion of the particles in the absence of an external field and calculate the diffusion tensor associated with the microscopic structure of the system. We show that particle-wall hydrodynamic interactions lead to non-linear effects in the mobility of different size particles. We explore the possibility of using such anisotropic media for the continuous separation of particles.