Confined active matter in external fields

TL;DR

This paper investigates how external fields influence the distribution and pressure of active particles confined between walls, revealing mechanisms to control active matter and prevent surface contamination.

Contribution

It introduces a comprehensive analysis of active particle behavior under combined confinement and external fields, highlighting control strategies for active matter systems.

Findings

Particles accumulate in low-speed regions in the bulk.

Orienting fields cause particles to align and accumulate downstream.

Strong fields can reorient particles away from walls, reducing surface pressure.

Abstract

We analyze a dilute suspension of active particles confined between walls and subjected to fields that can modulate particle speed as well as orientation. Generally, the particle distribution is different in the bulk compared to near the walls. In the bulk, particles tend to accumulate in the regions of low speed, but in the presence of an orienting field, particles rotate to align with the field and accumulate downstream in the field direction. At the walls, particles tend to accumulate pointing into the walls and thereby exert pressure on walls. But the presence of strong orienting fields can cause the particles to reorient away from the walls, and hence shows a possible mechanism for preventing contamination of surfaces. The pressure at the walls depends on the wall separation and the field strengths. This work demonstrates how multiple fields with different functionalities can be used to control active matter under confinement.