Magnetotaxis in droplet microswimmers

TL;DR

This paper demonstrates that weak magnetic fields can significantly influence the dynamics of self-propelling nematic microdroplets, revealing diverse behaviors depending on size, confinement, and field strength.

Contribution

It provides experimental evidence that weak diamagnetic torques can control active droplet microswimmers, expanding understanding of magnetotaxis in artificial active matter.

Findings

Weak magnetic fields alter droplet dynamics significantly.

Diverse dynamic modes observed with varying parameters.

Magnetotaxis can be achieved with sub-Tesla magnetic fields.

Abstract

Magnetotaxis is a well known phenomenon in swimming microorganisms which sense magnetic fields e.g. by incorporating crystalline magnetosomes. In designing artificial active matter with tunable dynamics, external magnetic fields can provide a versatile method for guidance. Here, it is the question what material properties are necessary to elicit a significant response. In this working paper, we document in experiments on self-propelling nematic microdroplets that the weak diamagnetic torques exerted by a sub-Tesla magnetic field are already sufficient to significantly affect the dynamics of these swimmers. We find a rich and nontrivial variety of dynamic modes by varying droplet size, state of confinement and magnetic field strength.