Banding, Excitability and Chaos in Active Nematic Suspensions

TL;DR

This paper investigates how active nematic suspensions exhibit complex behaviors like banding, oscillations, and chaos due to the interplay of activity, nematic order, and flow, using stability analysis and simulations.

Contribution

It introduces a model capturing the dynamic coupling of nematic order and flow, revealing new unstable and chaotic states in active suspensions.

Findings

Observation of spontaneous banded laminar flow

Identification of relaxation oscillations

Detection of chaotic flow regimes

Abstract

Motivated by the observation of highly unstable flowing states in suspensions of microtubules and kinesin, we analyze a model of mutually-propelled filaments suspended in a solvent. The system undergoes a mean-field isotropic-nematic transition for large enough filament concentrations when the nematic order parameter is allowed to vary in space and time. We analyze the model in two contexts: a quasi-one-dimensional channel with no-slip walls and a two-dimensional box with periodic boundaries. Using stability analysis and numerical calculations we show that the interplay between non-uniform nematic order, activity, and flow results in a variety of complex scenarios that include spontaneous banded laminar flow, relaxation oscillations, and chaos.