Vapor-powered boat

We present a novel self-propelling aquatic actuator inspired by Microvelia's movement, where the emission of a body fluid at the rear induces water-walking motions through the Marangoni force, rather than relying on mechanical forces like rowing or sliding. Previous soap- or cocktail-powered boats mimicked such mechanisms, but direct bulk mixing of liquid or solid fuel with water resulted in an instantaneous motion due to the rapid fuel consumption, and challenges in speed and direction control. To overcome these limitations, our study utilizes an alcohol vapor fuel to induce Marangoni force owing to the adsorption of alcohol vapor at the water-air interface, enabling sustainable movement on water surfaces with controllable speed and direction. We visualize these interfacial phenomena using a high-speed camera and Schlieren methods and construct a simple scaling model to rationalize the observed interfacial dynamics.