Dynamics of a linear magnetic "microswimmer molecule"

TL;DR

This paper investigates the dynamic behavior of a linear chain of three magnetic microswimmers connected by springs, revealing an oscillatory instability and corkscrew swimming trajectories as self-propulsion increases.

Contribution

It introduces a model of an active microswimmer molecule with magnetic and hydrodynamic interactions, analyzing its relaxation dynamics and instability mechanisms.

Findings

Oscillatory instability with increasing self-propulsion

Corkscrew-like swimming trajectories emerge

Potential for experimental verification with magnetic Janus particles

Abstract

In analogy to nanoscopic molecules that are composed of individual atoms, we consider an active "microswimmer molecule". It is built up from three individual magnetic colloidal microswimmers that are connected by harmonic springs and hydrodynamically interact with each other. In the ground state, they form a linear straight molecule. We analyze the relaxation dynamics for perturbations of this straight configuration. As a central result, with increasing self-propulsion, we observe an oscillatory instability in accord with a subcritical Hopf bifurcation scenario. It is accompanied by a corkscrew-like swimming trajectory of increasing radius. Our results can be tested experimentally, using for instance magnetic self-propelled Janus particles, supposably linked by DNA molecules.