Antipolar ordering of topological defects in active liquid crystals

TL;DR

This paper develops a minimal continuum theory to describe the antipolar ordering of topological defects in active liquid crystals formed by microtubule-kinesin bundles, linking experimental observations with a unified theoretical framework.

Contribution

It introduces a generalized Landau-de Gennes model that accounts for buckling and predicts antipolar order, bridging experimental data with theoretical understanding of active matter.

Findings

Model agrees with experimental data

Predicts antipolar order regime

Links active liquid crystals to quantum gases

Abstract

ATP-driven microtubule-kinesin bundles can self-assemble into two-dimensional active liquid crystals (ALCs) that exhibit a rich creation and annihilation dynamics of topological defects, reminiscent of particle-pair production processes in quantum systems. This recent discovery has sparked considerable interest but a quantitative theoretical description is still lacking. We present and validate a minimal continuum theory for this new class of active matter systems by generalizing the classical Landau-de Gennes free-energy to account for the experimentally observed spontaneous buckling of motor-driven extensile microtubule bundles. The resulting model agrees with recently published data and predicts a regime of antipolar order. Our analysis implies that ALCs are governed by the same generic ordering principles that determine the non-equilibrium dynamics of dense bacterial suspensions and elastic bilayer materials. Moreover, the theory manifests an energetic analogy with strongly interacting quantum gases. Generally, our results suggest that complex non-equilibrium pattern-formation phenomena might be predictable from a few fundamental symmetry-breaking and scale-selection principles.