Self-organisation of spermatozoa in bulk suspensions via unsteady elastohydrodynamic interactions

TL;DR

This paper presents a mechanical model showing that spermatozoa in bulk suspensions can self-organize into stable structures through unsteady elastohydrodynamic interactions, challenging traditional time-averaged stress theories.

Contribution

It introduces a novel self-organisation mechanism driven by unsteady hydrodynamics, advancing the understanding of active soft matter dynamics.

Findings

Spermatozoa form stable polar order via flagellar motion

Unsteady hydrodynamic interactions enable self-organisation

Contrasts with traditional time-averaged stress predictions

Abstract

We developed a mechanical model of spermatozoal swimming in bulk suspensions. We traced the spatiotemporal elastohydrodynamic interactions and found that spermatozoa engaged in self-organisation: flagellar undulatory motion generated a stable polar order. Conventional microswimmer theories use time-averaged stress fields to predict that the cellular structure is unstable. However, our present results reveal a novel self-organisation mechanism attributable to unsteady hydrodynamic interactions. We thus contribute to the theory of active soft matter dynamics.