Galloping Bubbles: spontaneous self-propulsion of vibrating bubbles along solid boundaries

Bubbles moving in a liquid are simple in appearance yet display a wealth of intriguing dynamics relevant to innumerable practical applications. Here, we demonstrate how confinement may prompt a symmetry-breaking of the harmonic shape oscillations of vibrating bubbles, leading to spontaneous self-propulsion along solid boundaries. We study the bubbles' spontaneous motion in terms of the key parameters of the system including bubble volume, driving frequency, and driving amplitude. Our results reveal that the dynamics of the self-propelling bubbles are intimately tied to their resonant responses to periodic forcing, which can be fine-tuned to produce a myriad of dynamics including rectilinear, circular, and zig-zag motions. Furthermore, we illustrate the ability of these bubbles to navigate complex geometries, as well as their emergent collective dynamics, including orbital states and self-assemblies.