The interplay between activity and filament flexibility determines the emergent properties of active nematics

Abstract: Active nematics are microscopically driven liquid crystals that exhibit dynamical steady states characterized by the creation and annihilation of topological defects. Motivated by experimental realizations of such systems made of biopolymer filaments and motor proteins, we describe a large-scale simulation study of a particle-based computational model that explicitly incorporates the semiflexibility of the biopolymers. We find that energy injected into the system at the particle scale preferentially excites bend deformations, renormalizing the filament bend modulus to smaller values. The emergent characteristics of the active nematic depend on activity and flexibility only through this activity-renormalized bend modulus, demonstrating that material parameters such as the Frank `constants' must explicitly depend on activity in a continuum hydrodynamic description of an active nematic. Further, we present a systematic way to estimate these material parameters from observations of deformation fields and defect shapes in experimental or simulation data.