Sustained vane rotation in a circular ratcheted Leidenfrost engine

This study investigates a vane-driven Leidenfrost engine based on evaporation-induced self-propulsion of liquid volumes of deionized water on a radially ratcheted circular substrate. Asymmetric surface topography rectifies vapor flow beneath the levitated liquid, creating pressure gradients and viscous shear stresses that generate tangential motion, which is converted into rotation by a surrounding ratcheted wall. During its lifetime, the liquid shape progresses through ring, arc, and spherical regimes. External vanes coupled to the rotating liquid convert the self-propulsive torque of the liquid into a mechanical output. The rotational dynamics of the engine are examined using two-, four-, and eight-blade vane configurations across a range of liquid volumes (1 to 10 mL) and substrate temperatures (280 to 400 °C). The liquid rapidly reached terminal rotation, attaining angular velocities up to ∼ 13 rad s −1 within 1 s. For a liquid volume of 1 0 m L at 360 °C, the vane achieves an angular velocity of approximately 1 2 r a d s −1 , with a maximum extracted torque at zero angular speed of approximately 8 0 0 μ ⁢ N m . Higher liquid volumes produced greater torque as a larger fraction of the ratcheted surface interacted with the moving liquid arc. The Leidenfrost engine operated continuously for more than an hour under continuous liquid replenishment, maintaining an average angular velocity of 1 1 r a d s −1 . These results indicate that vane-driven Leidenfrost engines offer a promising strategy for continuous microscale power generation.