Dynamics and Separation of Circularly Moving Particles in Asymmetric Patterned Arrays

摘要

There are many examples of driven and active matter systems containingparticles that exhibit circular motion with different chiralities, such asswimming bacteria near surfaces or certain types of self-driven colloidalparticles. Circular motion of passive particles can also be induced with anexternal rotating drive. Here we examine particles that move in circles andinteract with a periodic array of asymmetric L-shaped obstacles. We find aseries of dynamical phases as a function of swimming radius, including regimeswhere the particle motion is rectified, producing a net dc motion. Thedirection of the rectification varies with the swimming radius, permitting theseparation of particles with different swimming radii. Particles with the sameswimming radius but different chirality can also move in different directionsover the substrate and be separated. The rectification occurs for specificwindows of swimming radii corresponding to periodic orbits in which theparticles interact one or more times with the barriers per rotation cycle. Therectification effects are robust against the addition of thermal or diffusiveeffects, and are in some cases even enhanced by these effects.