Interface dynamics under nonequilibrium conditions: from a self-propelled droplet to dynamic pattern evolution

TL;DR

This paper investigates the instability of contact lines under nonequilibrium conditions through experiments on self-propelled droplets and dynamic pattern formation, supported by a theoretical model.

Contribution

It introduces experimental observations of self-propelled droplet motion and dynamic pattern formation, along with a theoretical model explaining contact line instability.

Findings

Self-propelled droplet exhibits spontaneous symmetry breaking and regular motion.

Dynamic labyrinthine patterns emerge from dewetting of metastable thin films.

Motion of contact lines is governed by diffusion processes.

Abstract

In this article, we describe the instability of a contact line under nonequilibrium conditions mainly based on the results of our recent studies. Two experimental examples are presented: the self-propelled motion of a liquid droplet and spontaneous dynamic pattern formation. For the self-propelled motion of a droplet, we introduce an experiment in which a droplet of aniline sitting on an aqueous layer moves spontaneously at an air-water interface. The spontaneous symmetry breaking of Marangoni-driven spreading causes regular motion. In a circular Petri dish, the droplet exhibits either beeline motion or circular motion. On the other hand, we show the emergence of a dynamic labyrinthine pattern caused by dewetting of a metastable thin film from the air-water interface. The contact line between the organic phase and aqueous phase forms a unique spatio-temporal pattern characterized as a dynamic labyrinthine. Motion of the contact line is controlled by diffusion processes. We propose a theoretical model to interpret essential aspects of the observed dynamic behavior.