Clustering and dynamic lane formation in active nematic phases of self-propelled, semiflexible polymers

Collective motions commonly form in anisotropic active matter systems of individually interacting particles, such as polar fluids, bacterial colonies, and eukaryotic cell tissues, closely resembling the ordered alignment observed in liquid crystals. Gliding assay experiments, or in vitro experiments observing cytoskeletal filaments such as actin and microtubules, have revealed diverse active matter phases, including long-range orientational order and various intermediate density regimes. We present Brownian Dynamics simulations to study the collective motion of self-propelled, semi-flexible filaments in gliding assays; active phases are largely dependent on the energy cost of filament overlap and rigidity in our model. Of particular interest is the jammed-flock intermediate density regime, characterized by "creature-like" clusters that continually dissolve, split, and merge. We demonstrate that both the internal dynamics of these clusters and the anisotropic structure of the surrounding fluid are strongly dependent on filament stiffness and bead density, and that the system relaxes into an active steady state of transient clusters when specific conditions are met. Finally, we also identify a negative feedback loop, where filaments form but destabilize ordered nematic lanes.