Dynamics and separation of circularly moving particles in asymmetrically patterned arrays

摘要

There are many examples of driven and active matter systems containing particles that exhibit circular motionnwith different chiralities, such as swimming bacteria near surfaces or certain types of self-driven colloidalnparticles. Circular motion of passive particles can also be induced with an external rotating drive. Here wenexamine particles that move in circles and interact with a periodic array of asymmetric L-shaped obstacles.nWe find a series of dynamical phases as a function of swimming radius, including regimes where the particlenmotion is rectified, producing a net dc motion. The direction of the rectification varies with the swimming radius,npermitting the separation of particles with different swimming radii. Particles with the same swimming radiusnbut different chirality can also move in different directions over the substrate and be separated. The rectificationnoccurs for specific windows of swimming radii corresponding to periodic orbits in which the particles interactnone or more times with the barriers per rotation cycle. The rectification effects are robust against the addition ofnthermal or diffusive effects, and are in some cases even enhanced by these effects.