Synchronization and collective motion of interfacial capillary spinners*

When a millimetric body is deposited onto the interface of a vibrating liquid bath, the relative motion between the object and interface generates outward propagating waves which leads to steady propulsion. Prior work has shown that chiral objects or "spinners" in isolation can rotate at a steady rate, with both the direction of rotation and angular speed depending sensitively on the spinner geometry and driving parameters. Here, we consider the capillary wave-mediated interactions of multiple spinners. We first characterize the two-spinner problem, demonstrating that spinners are able to stably synchronize their rotation in certain parameter regimes via their mutual wavefield. The many-body problem is then considered where a rich variety of static and dynamic interaction modes are found. A model of the spinner interaction is proposed, allowing us to draw analogy to other systems exhibiting spontaneous synchronization. This highly tunable and accessible system represents a new platform for studying active and driven systems interacting through deformable substrates.