Hydrodynamic Synchronisation of Chiral Microswimmers

TL;DR

This paper demonstrates through large-scale simulations that chiral microswimmers with different trajectories can spontaneously synchronize their rotation, leading to collective alignment and hydrodynamic synchronization in suspensions.

Contribution

It introduces a generic model for chiral microswimmers and shows their ability to spontaneously synchronize in bulk suspensions, a phenomenon not previously demonstrated.

Findings

Both circular and helical swimmers can synchronize their rotation.

Synchronization leads to high orientational order in velocity.

In racemic mixtures, intraspecies synchronization occurs without phase separation.

Abstract

We study synchronization in bulk suspensions of spherical microswimmers with chiral trajectories using large scale numerics. The model is generic. It corresponds to the lowest order solution of a general model for self-propulsion at low Reynolds numbers, consisting of a nonaxisymmetric rotating source dipole. We show that both purely circular and helical swimmers can spontaneously synchronize their rotation. The synchronized state corresponds to velocity alignment with high orientational order in both the polar and azimuthal directions. Finally, we consider a racemic mixture of helical swimmers where intraspecies synchronization is observed while the system remains as a spatially uniform fluid. Our results demonstrate hydrodynamic synchronization as a natural collective phenomenon for microswimmers with chiral trajectories.