Synchronized Rotations of Active Particles on Chemical Substrates

TL;DR

This paper models active particles on chemical substrates, revealing that activity and repulsion alone can induce synchronized rotations and phase separation, with potential applications in designing reorienting mechanical devices.

Contribution

It introduces a minimal model showing how chemo-phoretic interactions and activity lead to synchronized rotations without explicit alignment.

Findings

Emergence of synchronized rotations in active particles

Identification of a new cohesive clustering phase

Demonstration of rotation phenomena without explicit alignment

Abstract

Many microorganisms use chemical `signaling' - a quintessential self-organizing strategy in non-equilibrium - that can induce spontaneous aggregation and coordination in behavior. Using synthetic signaling as a design principle, we construct a minimal model of active Brownian particles (ABPs) having soft repulsive interactions on a chemically quenched patterned substrate. The interplay between chemo-phoretic interactions and activity is numerically investigated for a proposed variant of the Keller-Segel model for chemotaxis. Such competition not only results in a chemo-motility-induced phase-separated state but also a new cohesive clustering phase with synchronized rotations. Our results suggest that rotational order can emerge in systems by virtue of activity and repulsive interactions alone without an explicit alignment interaction. These rotations can also be exploited by designing mechanical devices that can generate reorienting torques using active particles.