Viscoelastic confinement induces periodic flow reversals in active nematics

TL;DR

This study investigates how viscoelastic confinement influences the behavior of active nematics, revealing a transition from steady flow to spontaneous oscillations with flow reversals due to the interplay of activity and elasticity.

Contribution

It introduces a combined linear stability analysis and hybrid lattice Boltzmann simulation approach to explore active nematics in viscoelastic channels, identifying conditions for oscillatory states.

Findings

Active nematics become unstable above a critical activity level.

High elasticity leads to steady flow states.

Low elasticity induces spontaneous oscillations with flow reversals.

Abstract

We use linear stability analysis and hybrid lattice Boltzmann simulations to study the dynamical behaviour of an active nematic confined in a channel made of viscoelastic material. We find that the quiescent, ordered active nematic is unstable above a critical activity. The transition is to a steady flow state for high elasticity of the channel surroundings. However, below a threshold elastic modulus, the system produces spontaneous oscillations with periodic flow reversals. We provide a phase diagram that highlights the region where time-periodic oscillations are observed and explain how they are produced by the interplay of activity and viscoelasticity. Our results suggest new experiments to study the role of viscoelastic confinement in the spatio-temporal organization and control of active matter.