Experimental Observation of Flow Fields Around Active Janus Spheres

TL;DR

This study experimentally measures flow fields around active Janus spheres, confirming propulsion mechanisms and advancing understanding of their hydrodynamic interactions and collective behavior.

Contribution

It provides the first detailed experimental flow field measurements around active Janus spheres, validating propulsion theories and enabling better modeling of their collective dynamics.

Findings

Flow fields around Janus spheres confirmed propulsion mechanism

Hydrodynamic interactions characterized for active colloids

Results support theoretical models of active particle behavior

Abstract

The hydrodynamic flow field around a catalytically active colloid is probed using particle tracking velocimetry both in the freely swimming state and when kept stationary with an external force. Our measurements provide information about the fluid velocity in the vicinity of the surface of the colloid, and confirm a mechanism for propulsion that was proposed recently. In addition to offering a unified understanding of the nonequilibrium interfacial transport processes at stake, our results open the way to a thorough description of the hydrodynamic interactions between such active particles and understanding their collective dynamics.