Active nematics with anisotropic friction: the decisive role of the flow aligning parameter

TL;DR

This study uses continuum simulations to explore how anisotropic friction influences active nematic flows, revealing distinct patterns like laning states or defect pairs depending on the flow-aligning behavior, and highlighting the importance of the flow aligning parameter.

Contribution

It demonstrates how anisotropic friction affects active nematic flow patterns and clarifies the role of the flow aligning parameter in these dynamics, supported by simulation results.

Findings

Flow-aligning regime produces laning states similar to experiments.

Flow-tumbling regime leads to bound defect pairs rather than laning.

Anisotropic friction significantly alters active nematic flow behaviors.

Abstract

We use continuum simulations to study the impact of anisotropic hydrodynamic friction on the emergent flows of active nematics. We show that, depending on whether the active particles align with or tumble in their collectively self-induced flows, anisotropic friction can result in markedly different patterns of motion. In a flow-aligning regime and at high anisotropic friction, the otherwise chaotic flows are streamlined into flow lanes with alternating directions, reproducing the experimental laning state that has been obtained by interfacing microtubule-motor protein mixtures with smectic liquid crystals. Within a flow-tumbling regime, however, we find that no such laning state is possible. Instead, the synergistic effects of friction anisotropy and flow tumbling can lead to the emergence of bound pairs of topological defects that align at an angle to the easy flow direction and navigate together throughout the domain. In addition to confirming the mechanism behind the laning states observed in experiments, our findings emphasise the role of the flow aligning parameter in the dynamics of active nematics.