Force generation in confined active fluids: The role of microstructure

TL;DR

This study experimentally links the force exerted by active particles on a passive probe to the particles' microstructure, confirming a universal relationship through experiments and minimal modeling.

Contribution

It demonstrates a direct, system-independent relationship between active particle microstructure and the forces they exert, validated by experiments and minimal numerical models.

Findings

Force on the probe correlates with particle density distribution.

Experimental results agree with minimal numerical model.

Established a general relationship between microstructure and force in active fluids.

Abstract

We experimentally determine the force exerted by a bath of active particles onto a passive probe as a function of its distance to a wall and compare it to the measured averaged density distribution of active particles around the probe. Within the framework of an active stress, we demonstrate that both quantities are - up to a factor - directly related to each other. Our results are in excellent agreement with a minimal numerical model and confirm a general and system-independent relationship between the microstructure of active particles and transmitted forces.