Run-and-Tumble Dynamics of Self-Propelled Particles in Confinement

TL;DR

This paper investigates how run-and-tumble bacteria accumulate near surfaces, revealing different density patterns based on run length distributions and deriving a universal accumulation law for large channels.

Contribution

It provides a theoretical and numerical analysis of microswimmer accumulation near surfaces, introducing a universal law applicable to various self-propelled particles.

Findings

Constant run lengths cause peaks and depletions in density near surfaces.

Exponentially-distributed run lengths produce different accumulation patterns.

A universal accumulation law is derived for large channel widths.

Abstract

Run-and-tumble dynamics is a wide-spread mechanism of swimming bacteria. The accumulation of run-and-tumble microswimmers near impermeable surfaces is studied theoretically and numerically in the low-density limit in two and three spatial dimensions. Both uni-modal and exponential distributions of the run lengths are considered. Constant run lengths lead to {peaks and depletions regions} in the density distribution of particles near the surface, in contrast to {exponentially-distributed run lengths}. Finally, we present a universal accumulation law for large channel widths, which applies not only to run-and-tumble swimmers, but also to many other kinds of self-propelled particles.