Active motion of contaminated microbubbles

Abstract

In many natural and technological multi-phase systems, bubbles are exposed to surface-active contaminants (surfactants) that may cover the whole or part of the bubble interface. A partial coverage of the interface may result in a spontaneous self-propulsion mechanism, which is yet not fully characterized. Here, the self-propulsion dynamics of partially contaminated bubbles is examined using high-fidelity simulations. The simulations enable a detailed picture of the flow physics and interfacial mechanisms driving the transient active motion. Results also show that for the case of viscous surrounding and negligible surface diffusion the duration of the active motion is inversely proportional to the contaminated area fraction, and the corresponding bubble displacement is directly proportional to the clean fraction.