Stability of liquid films covered by a carpet of self-propelled surfactant particles

TL;DR

This paper investigates how self-propelled surfactant particles at a liquid film interface influence the film's stability, revealing that their motion and rotational diffusion can either stabilize or destabilize the film depending on parameters.

Contribution

It introduces a model for the stability of liquid films covered by self-propelled particles, highlighting the complex effects of particle motion and rotational diffusion on film stability.

Findings

Rotational diffusion can stabilize or destabilize the film.

Different instability modes depend on particle velocity and diffusion strength.

Self-propelled particles significantly affect film surface stability.

Abstract

We consider a carpet of self-propelled particles at the liquid-gas interface of a liquid film on a solid substrate. The particles excert an excess pressure on the interface and also move along the interface while the swimming direction performs rotational diffusion. We study the intricate influence of these self-propelled insoluble surfactants on the stability of the film surface and show that depending on the strength of in-surface rotational diffusion and the absolute value of the in-surface swimming velocity several characteristic instability modes can occur. In particular, rotational diffusion can either stabilize the film or induce instabilities of different character.