Magnetically powered metachronal waves induce locomotion in self-assemblies

TL;DR

This paper demonstrates that precessing magnetic fields can induce metachronal waves in self-assembled ferromagnetic particles at liquid interfaces, enabling controllable locomotion inspired by biological cilia.

Contribution

It introduces a novel bioinspired swimming mechanism using magnetic fields to generate metachronal waves in particle assemblies, facilitating locomotion at low Reynolds number.

Findings

Precessing magnetic fields induce metachronal waves in particle assemblies.

The induced waves enable controllable locomotion similar to cilia.

The method works effectively with uniform magnetic fields at low Reynolds number.

Abstract

When tiny soft ferromagnetic particles are placed along a liquid interface and exposed to a vertical magnetic field, the balance between capillary attraction and magnetic repulsion leads to self-organization into well-defined patterns. Here, we demonstrate experimentally that precessing magnetic fields induce metachronal waves on the periphery of these assemblies, similar to the ones observed in ciliates and some arthropods. The outermost layer of particles behaves like an array of cilia or legs whose sequential movement causes a net and controllable locomotion. This bioinspired many-particle swimming strategy is effective even at low Reynolds number, using only spatially uniform fields to generate the waves.