Dynamics of magnetic microswimmers

Abstract

This work explores the dynamics of magnetic microswimmers composed of anisotropic hematite particles driven by external magnetic fields. We first measured the magnetic moment of ellipsoidal and peanut-shaped colloids by analyzing their reorientation under a static magnetic field. We then focused on achieving propulsion by applying a rotating field to the peanut-shaped particles and studying their motion near a solid-liquid interface. Specifically, we measured their average speed as a function of the field’s driving frequency during propulsion. We found two dynamic states separated by a critical frequency: a synchronous regime where colloids display increasing speed with frequency, and an asynchronous regime, where viscous drag dominates and speed decreases. The values of the critical frequencies were extracted from the experimental data for different field amplitudes. The results align with the theoretical model and show a form of non-reciprocal motion leading to propulsion in the low Reynolds number regime