Surface microswimmers, harnessing the interface to self-propel

TL;DR

This paper explores how interfaces can be exploited to enable self-propulsion of microscopic and small-scale swimmers, highlighting recent experiments and presenting new systems that utilize interface physics for locomotion.

Contribution

It introduces two novel systems of surface microswimmers powered by magnetic fields and demonstrates how interface forces can break symmetry for propulsion.

Findings

Floating ferromagnetic spheres assemble into swimming structures.

Magnetic field-driven centimeter-sized swimmers mimic water striders.

Interfaces can be harnessed to generate propulsion at low Reynolds number.

Abstract

In the study of microscopic flows, self-propulsion has been particularly topical in recent years, with the rise of miniature artificial swimmers as a new tool for flow control, low Reynolds number mixing, micromanipulation or even drug delivery. It is possible to take advantage of interfacial physics to propel these micro-robots, as demonstrated by recent experiments using the proximity of an interface, or the interface itself, to generate propulsion at low Reynolds number. This paper discusses how a nearby interface can provide the symmetry breaking necessary for propulsion. An overview of recent experiments illustrates how forces at the interface can be used to generate locomotion. This paper then presents original results concerning two systems. The first is composed of floating ferromagnetic spheres that assemble through capillarity into swimming structures. The second system, also powered by a magnetic field, is a centimeter-sized piece that swims similarly to water striders.