Shear flow of active matter in thin channels

We study the shear flow of active filaments confined in a thin channel for extensile and contractile fibers. We apply the Ericksen-Leslie equations of liquid crystal flow with an activity source term. The dimensionless form of this system includes the Ericksen, activity, and Reynolds numbers, together with the aspect ratio of the channel, as the main driving parameters. We perform a normal mode stability analysis of the base shear flow. For both types of fibers, we arrive at a comprehensive description of the stability properties and their dependence on the parameters of the system. The transition to unstable frequencies in extensile fibers occurs at a positive threshold value of the activity parameter, whereas for contractile ones a complex behavior is found at low absolute value of the activity number. The latter might be an indication of the biologically relevant plasticity and phase transition issues. In contrast with extensile fibers, flows of contractile ones are also found to be highly sensitive to the Reynolds number. The work on extensile fibers is guided by experiments on active filaments in confined channels and aims at quantifying their findings in the prechaotic regime.

Automated summary

The study investigates the shear flow of active filaments in a thin channel for both extensile and contractile fibers, analyzing the stability properties under different parameters. Extensile fibers transition to unstable frequencies at a positive threshold value of the activity parameter, while contractile fibers exhibit complex behavior at low absolute values of the activity number. Flow behaviors of contractile fibers are also highly sensitive to the Reynolds number compared to extensile fibers.