Effective interactions mediated between two permeable disks in an active fluid

Mahmoud Sebtosheikh,Ali Naji

doi:10.1038/s41598-020-71209-1

Mahmoud Sebtosheikh, Ali Naji

Open Access

https://doi.org/10.1038/s41598-020-71209-1

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Abstract

We study steady-state properties of a bath of active Brownian particles (ABPs) in two dimensions in the presence of two fixed, permeable (hollow) disklike inclusions, whose interior and exterior regions can exhibit mismatching motility (self-propulsion) strengths for the ABPs. We show that such a discontinuous motility field strongly affects spatial distribution of ABPs and thus also the effective interaction mediated between the inclusions through the active bath. Such net interactions arise from soft interfacial repulsions between ABPs that sterically interact with and/or pass through permeable membranes assumed to enclose the inclusions. Both regimes of repulsion and attractive (albeit with different mechanisms) are reported and summarized in overall phase diagrams.

Highlights

We study steady-state properties of a bath of active Brownian particles (ABPs) in two dimensions in the presence of two fixed, permeable disklike inclusions, whose interior and exterior regions can exhibit mismatching motility strengths for the ABPs
In the particular example of hard disklike inclusions that will be of interest here, the effective interaction between two such inclusions fixed within a two-dimensional active bath was shown to be predominantly repulsive[11,13,16,24], featuring nonmonotonic distance-dependent behaviors due to the mentioned ABP layering, or ring formation around the disks[18,20,23,24]
It is this asymmetric distribution of ABPs in and around the inclusions that causes an effective interaction force between them, which we shall explore

Summary

Introduction

We study steady-state properties of a bath of active Brownian particles (ABPs) in two dimensions in the presence of two fixed, permeable (hollow) disklike inclusions, whose interior and exterior regions can exhibit mismatching motility (self-propulsion) strengths for the ABPs. When the inclusions are placed at relatively large surface separations, the spatial distribution of ABPs around each of them exhibits radial symmetry, with a typical radial number density profile, ρ(r) , from the given inclusion center as shown in Fig. 2a for fixed d/σ = 8 , Pem = 40 and different Pec .

Results

Conclusion