Deformation of a soft boundary induced and enhanced by enclosed active particles

TL;DR

This study models how self-propelled particles confined by a deformable boundary cause shape changes, revealing two distinct deformation stages driven by particle activity levels.

Contribution

It introduces a two-dimensional simulation of active particles interacting with a deformable boundary, highlighting the cooperative deformation mechanisms at different activity regimes.

Findings

Boundary shape deforms with increasing active force.

Two deformation stages: local suppression and global shape change.

Different particle redistribution mechanisms at low and high concentrations.

Abstract

We simulate a two dimensional model of self-propelled particles confined by a deformable boundary. The particles tend to accumulate near the boundary and the shape of the boundary deforms upon the collisions. We find that there are two typical stages in the variation of the morphology with the increase of active force. One is at small force characterized by radially inhomogeneous redistribution of particles and suppression of local fluctuations of the boundary. The other is at large force featured by angularly redistribution of particles and global shape deformation of the boundary. The last two processes are strongly cooperative. We also find different mechanisms in the particle redistribution and opposite force-dependences of the rate of the shape variation at low and high particle concentrations.