Entropic barrier effect on mass transport in vertically vibrated granular systems
Zheng Peng1, Kiwing To2*
1School of Physics and Electronics, Central South University, Changsha, China
2Institute of Physics, Academia Sinica, Taipei, Taiwan
* presenting author:Kiwing To, email:ericto@gate.sinica.edu.tw
The entropic effect on the motion of a single millimeter size sphere confined in a quasi-two-dimensional asymmetrical channel in the horizontal plane under vertical vibration is explored experimentally. As driven by collisions with the rough base plate the sphere moves randomly and behaves like Brownian motion. The confinement of the asymmetrical channel provides entropic barrier and the entropy force drive the sphere to drift directional. It is found that the granular temperature of the sphere, which increased with increasing vibration strength, can be used to normalize the net drift speed. Furthermore we find that the position distribution within the channel is nontrivial and it is related to the net driving force on the sphere.

Keywords: Brownian motion, entropic force, asymmetrical channel