Transition boiling bubble powered micro-engine using a Leidenfrost bearing

Overcoming friction while generating useful torque is a challenge for micro engines. Here we report the development of a microscale engine that utilizes transition boiling as a mode of propulsion and the Leidenfrost effect as a friction-less bearing. The transition boiling micro engine shows significantly improved performance compared to a Leidenfrost engine, which uses vapor entrainment as a propulsion mechanism (up to 3 orders of magnitude higher efficiency). We characterise the performance of the transition boiling engine with temperature and develop an analytical model to model and compare the engine performance with experimental observations. Our results provide a new approach to generating torque with a virtually frictionless bearing in micro-engines unlocking applications in, e.g., remote sensing and low-grade energy harvesting.