Interacting Brownian particles exhibiting enhanced rectification in an asymmetric channel

Abstract

Rectification of interacting Brownian particles is investigated in a two-dimensional asymmetric channel in the presence of an external periodic driving force. The periodic driving force can break the thermodynamic equilibrium and induces rectification of particles (or finite average velocity). The spatial variation in the shape of the channel leads to entropic barriers, which indeed control the rectification of particles. We find that by simply tuning the driving frequency, driving amplitude, and shape of the asymmetric channel, the average velocity can be reversed. Moreover, a short range interaction force between the particles further enhances the rectification of particles greatly. This interaction force is modeled as the lubrication interaction. Interestingly, it is observed that there exists a characteristic critical frequency Ωc below which the rectification of particles greatly enhances in the positive direction with increasing the interaction strength; whereas, for the frequency above this critical value, it greatly enhances in the negative direction with increasing the interaction strength. Further, there exists an optimal value of the asymmetric parameter of the channel for which the rectification of interacting particles is maximum. These findings are useful in sorting out the particles and understanding the diffusive behavior of small particles or molecules in microfluidic channels, membrane pores, etc.