Suppression of Leidenfrost effect on superhydrophobic surfaces

The Leidenfrost phenomenon entails the levitation of a liquid droplet over a superheated surface, cushioned by its vapor layer. This vapor layer can obstruct boiling heat transfer in heat exchangers, thereby compromising energy efficiency and safety. For water, superhydrophobic surfaces are believed to reduce the Leidenfrost point (T-L)-the temperature at which this phenomenon occurs. Therefore, superhydrophobic surfaces are not commonly utilized in thermal machinery despite their benefits such as reducing frictional drag. Here, we demonstrate that it is possible to achieve superhydrophobicity without lowering T-L by surface engineering and fine-tuning liquid-solid adhesion. We demonstrate that T-L of water on superhydrophobic surfaces comprising doubly reentrant pillars (DRPs) can exceed that on hydrophilic and even superhydrophilic surfaces. Via theory and computation, we disentangle the contributions of microtexture, heat transfer, and surface chemistry on the onset of the Leidenfrost phenomenon. Remarkably, coating-free and superhydrophobic DRP architecture can facilitate similar to 300% greater heat transfer to water droplets at 200 degrees C in comparison with conventional superhydrophobic surfaces. These findings advance our understanding of the Leidenfrost phenomenon and herald technological applications of superhydrophobic surfaces in thermal machinery. (C) 2021 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

By surface engineering and fine-tuning liquid-solid adhesion, it is possible to achieve superhydrophobicity without lowering the Leidenfrost point. Water on superhydrophobic surfaces comprising doubly reentrant pillars (DRPs) can exceed that on hydrophilic and even superhydrophilic surfaces in terms of the Leidenfrost point.