Shear flow induced isotropic to nematic transition in a suspension of active filaments

TL;DR

This paper investigates how externally applied shear flow stabilizes the orientationally ordered phases of active filament suspensions, which are otherwise unstable at zero shear, with implications for biological and in vitro systems.

Contribution

It demonstrates that steady shear flow can stabilize both polar and apolar active filament phases, extending understanding of active hydrodynamics under shear conditions.

Findings

Shear flow stabilizes active filament phases that are unstable at zero shear.

Both polar and apolar phases are stabilized by sufficient shear.

Results are relevant to biological systems and in vitro experiments.

Abstract

We study the effects of externally applied shear flow on a model of suspensions of motors and filaments, via the equations of active hydrodynamics [PRL {\bf 89} (2002) 058101; {\bf 92} (2004) 118101]. In the absence of shear, the orientationally ordered phase of {\it both} polar and apolar active particles is always unstable at zero-wavenumber. An imposed steady shear large enough to overcome the active stresses stabilises both apolar and moving polar phases. Our work is relevant to {\it in vitro} studies of active filaments, the reorientation of endothelial cells subject to shear flow and shear-induced motility of attached cells.