Self-Propulsion of Liquid Marbles: Leidenfrost-Like Levitation Driven by the Marangoni Flow

TL;DR

This paper reports on the self-propulsion of liquid marbles on water surfaces driven by Marangoni flows caused by alcohol evaporation, with velocities around 0.1 m/s, influenced by alcohol concentration.

Contribution

It demonstrates a novel self-propulsion mechanism for liquid marbles driven by Marangoni flows and analyzes the effects of alcohol concentration and water drag.

Findings

Marbles achieve ~0.1 m/s velocity due to Marangoni flow.

Self-propulsion is suppressed by adding alcohol to water.

Marble velocity increases with alcohol concentration, independent of volume.

Abstract

Self-propulsion of liquid marbles filled with aqueous alcohol solutions and placed on a water surface is reported. The characteristic of velocity of the marbles is about 0.1 m/s. The phenomenon of self-propulsion is related to the Marangoni solutocapillary flow caused by the condensation of alcohol, evaporated from the liquid marble, on a water surface. The Marangoni flow in turn enhances the evaporation of alcohol from marbles. Addition of alcohol to the water supporting the marbles suppresses the self-propulsion. The propulsion of liquid marbles is mainly stopped by water drag. The velocity of the center of mass of marbles grows with the increase of the concentration of alcohol in a marble. The velocity of marbles self-propulsion is independent on their volume.