Experimental Investigation on Self-propulsion of Leidenfrost Droplets on Narrow Ratchet Surfaces

Liquid drops deposited on hot solid surface at the Leidenfrost temperature form a vapour cushion, producing self-propulsion, especially on ratchet surfaces. The study investigate this phenomenon and extends it to surface-modified hot aluminum surfaces. Experiments were carried out at Leidenfrost temperatures on normal ratchet and narrow-width ratchets to explore the self-propulsion of droplet by varying the droplet diameters. Experiments reveal that narrower ratchets relative to droplet diameter limit propulsion due to lower contact area, reduced vapour layer generation, and heat loss through the sidewalls. When normal and narrow-width ratchets are compared, the contact area between droplet and ratchet surface, vapour layer, and diameter of droplet has an impact on droplet self-propulsion.