Jamming of active particles in narrow pores: Implications for ratchet effect and diffusion coefficient

TL;DR

This paper investigates how active colloidal particles behave in narrow quasi-one-dimensional geometries, revealing effects like phase separation, ratchet-induced directed motion, and increased diffusion, using simulations and theoretical models.

Contribution

It introduces a combined numerical and analytical study of active particles in confined geometries, highlighting phenomena like ratchet effects and enhanced diffusion.

Findings

Active particles exhibit motility-induced phase separation.

Broken spatial symmetry induces a ratchet effect.

Confinement enhances the diffusion coefficient.

Abstract

We study the behavior of colloidal active particles interacting via steric repulsion in various quasi-1D geometries. We mainly focus on active particles with high P\'eclet number. We discuss 3 phenomena closely tied to those systems: motility-induced phase separation (or dynamical freezing), ratchet effect (which takes place if the geometry has broken spatial symmetry), and the enhanced diffusion coefficient. We study those particles using numerical simulations employing an ASEP-like model. Besides direct numerical simulations we study the model by mean-field approximation and by solving the coarse-grained hydrodynamic equations.