Restoring-torque-induced current reversal and transport enhancement in confined active matter systems.

Previous studies about directed transport of active matter have overlooked the restoring torques arising from confinement that significantly impact the collective behavior. We numerically investigated the transport of active particles experiencing restoring torques (coupling the steric and confining forces) in a periodic channel. It is demonstrated that restoring torques can significantly enhance the rectification, and can induce current reverse. With a fixed positive asymmetry parameter, the scaled average velocity shows a peak function in the negative direction as the restoring torque increases, and after current reversal, it presents a peak function in the positive direction. When the restoring torque is an intermediate value, current reverse can occur by varying the self-propulsion speed or packing fraction. Our results may contribute to a better understanding of the effects of confinement with restoring torques on the collective behavior of active matter, and provide a theoretical foundation for related experimental investigations of active matter transport.