Emergent Polar Organization and Bundling of Nematic Filaments Driven by Crosslinking Motors

Mixtures of cytoskeletal filaments and molecular motors can create active nematic liquid crystals with remarkable properties, including spontaneously generated extensile stress, active turbulent flow, and complex defect dynamics. We have developed a minimal computational model of a network of rigid filaments that undergoes bundling and sliding by crosslinking motor proteins. Here, we map the phase diagram as motor activity and concentration are varied. Increasing the concentration of passive crosslinkers drives a transition from isolated, laterally extended bundles to horizontally extended nematic domains. Low driving of the bundled state maintains the extended bundle organization but polarity sorts these rod aggregates. Sufficiently high driving leads to large, fluctuating polar domains and apparent polar phase separation. We characterize the polarity-dependent filament transport that leads to emergent polar organization of the non-equilibrium steady state.