Controlled motion of Janus particles in periodically phase-separating binary fluids

TL;DR

This study numerically explores how Janus particles move in periodically phase-separating binary fluids, revealing a cycle-driven propulsion mechanism influenced by wettability and fluid composition.

Contribution

It introduces a novel understanding of Janus particle propulsion driven by cyclic phase separation and wettability effects in binary fluids.

Findings

Particle moves unboundedly toward the head during cycles

Motion depends on fluid composition and cycle frequency

Hydrodynamic flow is key to propulsion mechanism

Abstract

We numerically investigate the propelled motions of a Janus particle in a periodically phase-separating binary fluid mixture. In this study, the surface of the particle tail prefers one of the binary fluid components and the particle head is neutral in the wettability. During the demixing period, the more wettable phase is selectively adsorbed to the particle tail. Growths of the adsorbed domains induce the hydrodynamic flow in the vicinity of the particle tail, and this asymmetric pumping flow drives the particle toward the particle head. During the mixing period, the particle motion almost ceases because the mixing primarily occurs via diffusion and the resulting hydrodynamic flow is negligibly small. Repeating this cycle unboundedly moves the Janus particle toward the head. The dependencies of the composition and the repeat frequency on the particle motion are discussed.