Motor crosslinking augments elasticity in active nematics

TL;DR

This study investigates how microscopic properties like motor processivity and crosslinking influence the elasticity and flow behavior of active nematic materials, combining experiments and multiscale modeling.

Contribution

It reveals that filament crosslinking by motors and passive crosslinkers significantly enhances nematic elasticity and affects flow dynamics, providing a link between microscopic motor properties and macroscopic material behavior.

Findings

Crosslinking dominates nematic elasticity contributions.

Motor speed nonmonotonically affects nematic flow.

Passive crosslinking controls energy transfer into flow.

Abstract

In active materials, uncoordinated internal stresses lead to emergent long-range flows. An understanding of how the behavior of active materials depends on mesoscopic (hydrodynamic) parameters is developing, but there remains a gap in knowledge concerning how hydrodynamic parameters depend on the properties of microscopic elements. In this work, we combine experiments and multiscale modeling to relate the structure and dynamics of active nematics composed of biopolymer filaments and molecular motors to their microscopic properties, in particular motor processivity, speed, and valency. We show that crosslinking of filaments by both motors and passive crosslinkers not only augments the contributions to nematic elasticity from excluded volume effects but dominates them. By altering motor kinetics we show that a competition between motor speed and crosslinking results in a nonmonotonic dependence of nematic flow on motor speed. By modulating passive filament crosslinking we show that energy transfer into nematic flow is in large part dictated by crosslinking. Thus motor proteins both generate activity and contribute to nematic elasticity. Our results provide new insights for rationally engineering active materials.