Banding, excitability and chaos in active nematic suspensions

Abstract

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