Non-equilibrium capillary self-assembly

Existing, well-established principles of interfacial capillary self-assembly focus on the behavior of such systems at equilibrium, wherein the resultant self-assembled structures reside in a local minimum of a free-energy landscape. Inspired by recent experiments involving overdamped, microscopic colloids, we herein study experimentally and theoretically the structural rearrangements between ground states of clusters of millimetric spheres bound by capillary attractions. The structural rearrangements are driven by chaotic Faraday waves, which in turn play the role of an active bath. In contrast to colloids, inertial effects are non-negligible in our macroscopic system, prompting the development of a Langevin model of the particle dynamics, informed by the fundamental aspects of the fluid system. Our highly tunable experimental system addresses the relative paucity of model systems for studying inertial active and driven matter and informs new directions for non-invasive, directed self-assembly at the macroscale.