Fission and fusion scenarios for magnetic microswimmer clusters

TL;DR

This paper investigates how magnetic microswimmer clusters undergo fission and fusion, revealing diverse behaviors influenced by hydrodynamic and dipolar interactions, with implications for active colloids and bacteria.

Contribution

It introduces new insights into the fission and fusion dynamics of magnetic microswimmer clusters, highlighting the effects of swimmer type and interactions.

Findings

Puller chains are stable while pusher chains disassemble with increased propulsion.

Ring clusters undergo fission regardless of swimmer type.

Multiple fusion scenarios occur during collisions of swimmers with ring clusters.

Abstract

Fission and fusion processes of particles clusters occur in many areas of physics and chemistry from subnuclear to astronomic length scales. Here we study fission and fusion of magnetic microswimmer clusters as governed by their hydrodynamic and dipolar interactions. Rich scenarios are found which depend crucially on whether the swimmer is a pusher or a puller. In particular a linear magnetic chain of pullers is stable while a pusher chain shows a cascade of fission (or disassembly) processes as the self-propulsion velocity is increased. Contrarily, magnetic ring clusters show fission for any type of swimmer. Moreover, we find a plethora of possible fusion (or assembly) scenarios if a single swimmer collides with a ringlike cluster and two rings spontaneously collide. Our predictions are obtained by computer simulations and verifiable in experiments on active colloidal Janus particles and magnetotactic bacteria.