Directed Motion of Elongated Active Polymers
  Previous work shows that a net directed motion arises from a system of individual particles undergoing run-and-tumble dynamics in the presence of an array of asymmetric barriers. Here, we show that when the individual particle is replaced by a chain of particles linked to each other by spring forces (polymer), the rectification is enhanced. It is found that the rectification increases when the number of particles in each polymer, as well as its length, increases. In addition, the rectification increases when the size of the opening between neighboring funnel tips, lo, decreases. Interestingly, if the conformal entropic difference exceeds the thermal diffusion, net directed motion is observed even when the run-and-tumble dynamics approaches Brownian motion. Also, when the inelastic collisions between the particles and the barriers are replaced by elastic collisions, a reversed rectification is observed. 
Mew-Bing Wan, YongSeok Jho
cond-mat.soft cond-mat.stat-mech