Guided motion of kinked vesicles by active particles

Collective motion of active particles has been studied extensively, yet effective strategies to navigate active particle swarms are still rare and rely on external guidance. We introduce a method to control the trajectories of swarms of active rod-like particles by confining them within a rigid bounding membrane (vesicle) of non-uniform shape. We show that the propelling agents spontaneously form clusters at the membrane wall and collectively propel the vesicle, turning it into an active superstructure. To steer the motion of the superstructure, we add a kink to the bounding membrane that directs the motion of the vesicle. We show how the system's geometrical and material properties, such as the aspect ratio and Péclet number of the active rods, along with the kink angle and flexibility of the membrane, determine the stacking of active particles at the kink. The stacking induces different types of vesicle motion, including kink-forward linear motion, kink-backward linear motion, and circular motion. Based on our findings, we designed vesicles with switchable and reversible motions triggered by external forces that change specific properties of the system. The observed phenomena suggest a promising strategy for steering vesicles and other confining soft matter systems and, conversely, a promising approach to particle transport and swarm control. Finally, we show how kinked vesicles can also serve to navigate active matter through complex and tortuous environments.