Dancing marbles: viscous liquid marbles on vibrating incline

We investigate the dynamics of soft liquid marbles composed of viscous droplets encapsulated by hydrophobic powder, placed on a vibrating inclined plane. These “dancing marbles” exhibit rich locomotion behaviors—bouncing, rolling, and directional motion—when subjected to vertical sinusoidal vibrations. The use of hydrophobic powder prevents the direct contact between the droplet and the substrate, enabling non-wetting behavior and minimizing dissipation at the contact interface.

Systematic experiments are conducted by varying the marble size, viscosity, vibration frequency, amplitude, and inclination angle. We identify critical conditions under which the marbles begin to self-propel uphill or downhill, and analyze their average velocity as a function of radius and driving parameters. The observed behaviors are governed by a complex interplay between gravity, capillarity, inertia, and the transient contact dynamics induced by vertical impacts with the substrate.

We present a phase diagram of marble motion regimes—pinned, bouncing, rolling, and directional locomotion—and quantify the transition thresholds between them. High-speed imaging reveals periodic deformation and retraction at the contact zone, with the contact time and contact area modulated by the vibration phase and frequency.

This study provides insights into energy conversion mechanisms at liquid–solid–air interfaces in a non-wetting regime