Thermal Brownian motor

Granular Brownian motors: role of gas anisotropy and inelasticity

We investigate the motion of a two-dimensional wedge-shaped object (a granular Brownian motor), which is restricted to move along the x axis and cannot rotate as gas particles collide with it. We show that its steady-state drift, resulting from inelastic gas-motor collisions, is dramatically affected by anisotropy in the velocity distribution of the gas. We identify the dimensionless parameter providing the dependence of this drift on shape, masses, inelasticity, and anisotropy: The anisotropy leads to dramatically enhanced drift of the motor, which should easily be visible in experimental realizations.

Rectifying the thermal Brownian motion of three-dimensional asymmetric objects

We extend the analysis of a thermal Brownian motor reported by Van den Broeck [Phys. Rev. Lett. 93, 090601 (2004)] to a three-dimensional configuration. We calculate the friction coefficient, diffusion coefficient, and drift velocity as functions of shape and present estimates based on physically realistic parameter values.