Collective dynamics in active polar polymer assemblies

Tangentially driven active polymers, model systems for motor-driven filaments, have been extensively studied in uniform activity fields. Here, we show that an activity gradient breaks fore-aft symmetry, generating net body forces that steer dimers, asters, and larger assemblies toward high-activity regions. Including temporal stochasticity softens the chains, allowing them to bend and wind around other filaments. Once several contacts are established, steric interlocking arrests relative motion and stabilizes the assembly into a hierarchically entangled cluster. These clusters persist for times far exceeding single-chain relaxation and do not appear under deterministic, temporally constant activity. Remarkably, such activity-induced gelation occurs even at polymer concentrations substantially lower than those typically required for passive chains. Our results reveal a mechanism for activity-induced aggregation, providing strategies for designing autonomous and reconfigurable microfluidic systems.