Biased Brownian motion in a channel with symmetry and anisotropy

We study biased Brownian motion of a bead in a quasi-two-dimensional horizontal channel consists of identical cells with asymmetric walls and anisotropic base connected in a circular loop. When the channel is shaken vertically, energy is injected to the bead by collisions with the base and converted to kinetic energy in the horizontal direction. Asymmetry and anisotropy of channel induce a driving force on the bead so that the bead performs biased Brownian motion along the channel axis with the drift velocity being proportional to the diffusivity. Furthermore, the distribution function of the escape time from a cell is found to be an exponentially decay function. These experimental results can be explained by the continuous time random walk theory (CTRW).