Activity induced nematic order in isotropic liquid crystals

TL;DR

This paper demonstrates through analysis and simulations that active isotropic liquids of elongated particles can spontaneously develop nematic order due to activity, especially under flow-aligning conditions.

Contribution

It introduces a linear stability analysis showing activity-induced nematic order in isotropic phases, supported by numerical hydrodynamic simulations.

Findings

Active particles can induce nematic order from isotropic states.

Flow-aligning particles favor ordering.

The instability differs from known active nematic instabilities.

Abstract

We use linear stability analysis to show that an isotropic phase of elongated particles with dipolar flow fields can develop nematic order as a result of their activity. We argue that ordering is favoured if the particles are flow-aligning and is strongest if the wavevector of the order perturbation is neither parallel nor perpendicular to the nematic director. Numerical solutions of the hydrodynamic equations of motion of an active nematic confirm the results. The instability is contrasted to the well-known hydrodynamic instability of an ordered active nematic.