Phase separation of chemokinetic active particles

TL;DR

This paper investigates how chemokinesis influences motility-induced phase separation in active particles, revealing that chemical consumption modes can either enhance or suppress phase separation and lead to diverse pattern formations.

Contribution

It introduces a hydrodynamic theory and demonstrates how different chemokinetic coupling regimes affect MIPS and pattern formation in active particles.

Findings

MIPS is intensified when chemical consumption scales with particle density.

MIPS is suppressed when chemical consumption is linked to particle motion.

Different chemokinetic regimes lead to large-scale coarsening or microphase separation.

Abstract

Motility-induced phase separation (MIPS) is a well-studied nonequilibrium collective phenomenon observed in active particles. Recently, there has been growing interest in how coupling the self-propulsion of active particles to chemical degrees of freedom affects MIPS. Although the effects of chemotaxis on MIPS have been extensively studied, little is known about how chemokinesis affects MIPS. In this study, we demonstrate that various patterns can be induced when active particles consume chemicals and exhibit chemokinesis, where higher chemical concentrations enhance self-propulsion without causing alignment with the chemical gradient. We discover that MIPS is intensified if chemical consumption is proportional to particle density (as in the basal metabolic regime), but it is suppressed if chemical consumption is closely tied to particle motion (as in the active metabolic regime). While the former produces large-scale phase separation via coarsening, the latter suppresses the coarsening process, leading to microphase separation and oscillating patterns. We also derive a hydrodynamic theory that describes these findings.