Chemotactic motility-induced phase separation

TL;DR

This paper investigates how collective chemotaxis influences motility-induced phase separation (MIPS) in active matter, revealing that chemotaxis can suppress, arrest, or alter phase separation, leading to new dynamic behaviors.

Contribution

It introduces a theoretical and simulation-based analysis of the competition between chemotaxis and MIPS, providing quantitative principles for understanding active matter systems with chemotactic behavior.

Findings

Chemotaxis can suppress or arrest MIPS in active systems.

Chemotactic interactions lead to new dynamic instabilities.

The study establishes quantitative criteria for chemotaxis-MIPS competition.

Abstract

Collectives of actively-moving particles can spontaneously separate into dilute and dense phases -- a fascinating phenomenon known as motility-induced phase separation (MIPS). MIPS is well-studied for randomly-moving particles with no directional bias. However, many forms of active matter exhibit collective chemotaxis, directed motion along a chemical gradient that the constituent particles can generate themselves. Here, using theory and simulations, we demonstrate that collective chemotaxis strongly competes with MIPS -- in some cases, arresting or completely suppressing phase separation, or in other cases, generating fundamentally new dynamic instabilities. We establish quantitative principles describing this competition, thereby helping to reveal and clarify the rich physics underlying active matter systems that perform chemotaxis, ranging from cells to robots.