The 9th International Conference on Surface Engineering (ICSE 2024)

The Leidenfrost phenomenon, wherein a droplet is levitated by its own vapor when placed on a heated surface, plays a crucial role in droplet manipulation, spray cooling, and drag reduction. The essential emergence sign of the Leidenfrost phenomenon is the formation of continuous vapor film beneath the droplet. Rough hydrophobic surfaces are believed to accelerate vapor film formation due to their low adhesion energy and reduced liquid-solid contact area. Therefore, hydrophobic surfaces usually have lower Leidenfrost points than other surfaces, which induces a deterioration of heat transfer between droplets and surfaces. However, here we found exceptions. Through high-speed imaging, we found that the hydrophobic doubly reentrant structures can significantly suppress the emergence of the Leidenfrost phenomenon between a water droplet and a superheated surface. Specifically, a superhydrophobic surface rendered with doubly reentrant pillars can prevent the appearance of the Leidenfrost phenomenon until ~363 °C, while a hydrophobic surface decorated with doubly reentrant cavities can inhibit the Leidenfrost phenomenon even when the surface temperature reaches 440 °C. Experimental and theoretical investigations were performed to reveal the physics of these counterintuitive phenomena. These findings advance our concepts of the Leidenfrost phenomenon and may open a door to enhance heat transfer on hydrophobic surfaces.

Leidenfrost Phenomenon,Micro/nano Fabrication,Surface Structures,Interfacial Tension,Heat Transfer