Transient coarsening and the motility of optically heated Janus colloids in a binary liquid mixture

Abstract

A gold-capped Janus particle suspended in a near-critical binary liquid mixture can self-propel under illumination. We have immobilized such a particle in a narrow channel and studied the nonequilibrium dynamics of a binary solvent around it, using experiment and numerical simulations. For the latter we consider both a purely diffusive and a hydrodynamic model. All approaches indicate that the early time dynamics is purely diffusive and characterized by composition layers traveling with a constant speed from the surface of the colloid into the bulk. Subsequently, hydrodynamic effects set in and the transient state is destroyed by strong nonequilibrium concentration fluctuations, which arise as a result of the temperature gradient and the vicinity of the critical point of the binary liquid mixture. They give rise to a complex, permanently changing coarsening patterns. For a mobile particle, the transient dynamics results in propulsion in the direction opposite to that observed after the steady state is attained.

39 pages, 20 figures

References in corpus (4)

• Gravitaxis of asymmetric self-propelled colloidal particles
• Light-switchable propulsion of active particles with reversible interactions
• Tuning the motility and directionality of self-propelled colloids
• Droplet evaporation in one-component fluids: Dynamic van der Waals theory

Cited by in corpus (3)

• A Brownian cyclic engine operating in a viscoelastic active suspension
• Work extraction and performance of colloidal heat engines in viscoelastic baths
• Relaxation to steady states of a binary liquid mixture around an optically heated colloid