Author(s): Thibault Lefranc, Alberto Dinelli, Carla Fernández-Rico, Roel P. A. Dullens, Julien Tailleur, and Denis Bartolo Microscopic self-propelled rods with built-in quorum sensing adapt their motion to local crowding—rolling in sparse areas and halting in dense ones—leading to dynamic pattern formation and collective freezing behavior. [Phys. Rev. X 15, 031050] Published Fri Aug 22, 2025