Self propelled particle transport in regular arrays of rigid asymmetric obstacles

TL;DR

This study demonstrates that self-propelled particles can achieve directed transport in regular arrays of convex obstacles through collective motion, without external fields or alignment rules, driven mainly by surface attachment tendencies.

Contribution

It reveals how collective behavior of SPP around convex obstacles induces net transport, a novel insight into active matter in structured environments.

Findings

SPP exhibit vortex motion around symmetric obstacles.

A steady particle current emerges without external fields.

Transport is driven by surface attachment tendencies.

Abstract

We report numerical results which show the achievement of net transport of self-propelled particles (SPP) in the presence of a two-dimensional regular array of convex, either symmetric or asymmetric, rigid obstacles. The repulsive inter-particle (soft disks) and particle-obstacle interactions present no alignment rule. We find that SPP present a vortex-type motion around convex symmetric obstacles even in the absence of hydrodynamic effects. Such a motion is not observed for a single SPP, but is a consequence of the collective motion of SPP around the obstacles. An steady particle current is spontaneously established in an array of non-symmetric convex obstacle (which presents no cavity in which particles may be trapped in), and in the absence of an external field. Our results are mainly a consequence of the tendency of the self-propelled particles to attach to solid surfaces.