Shearing active gels close to the isotropic-nematic transition

TL;DR

This study numerically investigates the rheological behavior of active gels near the isotropic-nematic transition, revealing size, boundary, and phase-dependent flow properties, including viscosity divergence and shear banding.

Contribution

It provides new insights into the flow behavior of active gels near phase transition, highlighting activity-induced discontinuities and complex flow patterns.

Findings

Viscosity diverges in contractile systems near transition.

Shear-banded flow with zero viscosity in extensile suspensions.

Flow behavior strongly depends on sample size and boundary conditions.

Abstract

We study numerically the rheological properties of a slab of active gel close o the isotropic-nematic transition. The flow behavior shows strong dependence on sample size, boundary conditions, and on the bulk constitutive curve, which, on entering the nematic phase, acquires an activity-induced discontinuity at the origin. The precursor of this within the metastable isotropic phase for contractile systems ({\em e.g.,} actomyosin gels) gives a viscosity divergence; its counterpart for extensile ({\em e.g.,} {\em B. subtilis}) suspensions admits instead a shear-banded flow with zero apparent viscosity.