Microswimmers knead nematics into cholesterics

Fuente: arXiv
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Auteurs principaux: Gautam, Bhavesh, Lintuvuori, Juho
Format: Preprint
Publié: 2024
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author Gautam, Bhavesh
Lintuvuori, Juho
author_facet Gautam, Bhavesh
Lintuvuori, Juho
contents The hydrodynamic stresses created by active particles can destabilise orientational order present in the system. This is manifested, for example, by the appearance of a bend instability in active nematics or in quasi-2-dimensional living liquid crystals consisting of swimming bacteria in thin nematic films. Using large-scale scale hydrodynamics simulations, we study a system consisting of spherical microswimmers within a 3-dimensional nematic liquid crystal. We observe a spontaneous chiral symmetry breaking, where the uniform nematic state is kneaded into a continously twisting state, corresponding to a helical director configuration akin to a cholesteric liquid crystal. The transition arises from the hydrodynamic coupling between the liquid crystalline elasticity and the swimmer flow fields, leading to a twist-bend instability of the nematic order. It is observed for both pusher (extensile) and puller (contractile) swimmers. Further, we show that the liquid crystal director and particle trajectories are connected: in the cholesteric state the particle trajectories become helicoidal.
format Preprint
id arxiv_https___arxiv_org_abs_2401_05262
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Microswimmers knead nematics into cholesterics
Gautam, Bhavesh
Lintuvuori, Juho
Soft Condensed Matter
The hydrodynamic stresses created by active particles can destabilise orientational order present in the system. This is manifested, for example, by the appearance of a bend instability in active nematics or in quasi-2-dimensional living liquid crystals consisting of swimming bacteria in thin nematic films. Using large-scale scale hydrodynamics simulations, we study a system consisting of spherical microswimmers within a 3-dimensional nematic liquid crystal. We observe a spontaneous chiral symmetry breaking, where the uniform nematic state is kneaded into a continously twisting state, corresponding to a helical director configuration akin to a cholesteric liquid crystal. The transition arises from the hydrodynamic coupling between the liquid crystalline elasticity and the swimmer flow fields, leading to a twist-bend instability of the nematic order. It is observed for both pusher (extensile) and puller (contractile) swimmers. Further, we show that the liquid crystal director and particle trajectories are connected: in the cholesteric state the particle trajectories become helicoidal.
title Microswimmers knead nematics into cholesterics
topic Soft Condensed Matter
url https://arxiv.org/abs/2401.05262