Active nematic materials with substrate friction

TL;DR

This paper investigates how substrate friction influences active turbulence in dense active nematic materials, revealing a transition from increased defect activity to a jammed state with banded flow patterns.

Contribution

It introduces a model describing the effects of substrate friction on active turbulence, highlighting the transition from defect proliferation to a jammed, shear-banded regime.

Findings

Increased friction reduces wall spacing in nematic director fields.

Higher friction leads to more topological defects.

At high friction, the system exhibits shear-banded, jammed states.

Abstract

Active turbulence in dense active systems is characterized by high vorticity on a length scale that is large compared to that of individual entities. We describe the properties of active turbulence as momentum propagation is screened by frictional damping. As friction is increased, the spacing between the walls in the nematic director field decreases as a consequence of the more rapid velocity decays. This leads to, first, a regime with more walls and an increased number of topological defects, and then to a jammed state in which the walls deliminate bands of opposing flow, analogous to the shear bands observed in passive complex fluids.