Harnessing confinement and driving to tune active particle dynamics

TL;DR

This paper demonstrates how confining a granular active particle in a quasi-one-dimensional channel induces run-and-tumble dynamics, which can be externally controlled, offering new ways to tune active particle behavior.

Contribution

It introduces a method to control active noise in particles through geometric confinement and external driving, revealing emergent run-and-tumble dynamics in a granular self-propelled particle.

Findings

Confinement induces run-and-tumble behavior in active particles.

The particle's orientation dynamics map to a Brownian particle in a periodic potential.

External driving allows explicit control of the emergent noise parameters.

Abstract

A distinguishing feature of active particles is the nature of the non-equilibrium noise driving their dynamics. Control of these noise properties is, therefore, of both fundamental and applied interest. We demonstrate emergent tuning of the active noise of a granular self-propelled particle by confining it to a quasi one-dimensional channel. We find that this particle, moving like an active Brownian particle (ABP) in two-dimensions, displays run-and-tumble (RTP) characteristics in confinement. We show that the dynamics of the relative orientation co-ordinate of the particle maps to that of a Brownian particle in a periodic potential subject to a constant force, in analogy to the dynamics of a molecular motor. This mapping captures the essential statistical characteristics of the one-dimensional RTP motion. Specifically, our theoretical analysis is in agreement with the empirical distributions of the relative orientation co-ordinate and the run-times (tumble-rates) of the particle. Finally, we explicitly control these emergent run-and-tumble like noise parameters by external driving. Altogether, our work illustrates geometry-induced tuning of the active dynamics of self-propelled units thus suggesting an independent route to harness their internal dynamics.