Emergent Synchronization and Locomotion in Softly Confined Active Matter

Active matter systems of self-propelled particles display a wide variety of emergent behaviors under confinement. Using combined experimental and simulation results, we demonstrate the dynamical coupling between a soft, mobile boundary and a collection of non-chiral self-propelled robots confined within it. By tuning the boundary's compliance and mobility, the system transitions from disordered motion to a synchronized state of the enclosed particles, which in turn drives sustained rotation and locomotion of the boundary itself. These results demonstrate a reciprocal feedback mechanism between active matter and soft materials, where the collective dynamics of the particles and the motion of the boundary co-emerge, establishing a macroscopic tunable platform for studying dynamics of self-organized, self-spinning systems.