Mechanisms of carrier transport induced by a microswimmer bath

TL;DR

This study models how microswimmer interactions influence the directed transport of a wedge-shaped carrier, revealing dependence on swimmer alignment and shape for optimal efficiency.

Contribution

It provides a detailed simulation-based analysis of microswimmer-induced carrier transport, highlighting the effects of interaction models and swimmer alignment on transport mechanisms.

Findings

Transport is optimal in turbulent states with swirl depletion for weak alignment.

In strong alignment, optimal transport occurs in dilute regimes via a polar swimmer cloud.

Carrier shape affects maximum transport speed depending on interaction type.

Abstract

Recently, it was found that a wedgelike microparticle (referred to as "carrier") which is only allowed to translate but not to rotate exhibits a directed translational motion along the wedge cusp if it is exposed to a bath of microswimmers. Here we model this effect in detail by resolving the microswimmers explicitly using interaction models with different degrees of mutual alignment. Using computer simulations we study the impact of these interactions on the transport efficiency of V-shaped carrier. We show that the transport mechanisms itself strongly depends on the degree of alignment embodied in the modelling of the individual swimmer dynamics. For weak alignment, optimal carrier transport occurs in the turbulent microswimmer state and is induced by swirl depletion inside the carrier. For strong aligning interactions, optimal transport occurs already in the dilute regime and is mediated by a polar cloud of swimmers in the carrier wake pushing the wedge-particle forward. We also demonstrate that the optimal shape of the carrier leading to maximal transport speed depends on the kind of interaction model used.