Increasing Leidenfrost point using micro-nano hierarchical surface structures

The Leidenfrost effect is undesirable in cooling applications as the vapor layer on which the liquid levitates acts as a heat transfer barrier. Here, we report on increasing the Leidenfrost temperature by surface textures that can promote droplet wetting at high superheat via capillary wicking. Counterintuitively, we find that sparser rather than denser textures increase the Leidenfrost temperature. Our experimental results are consistent with a physical model that balances capillary wetting pressures with dewetting pressures exerted by the escaping vapor. The physical mechanism suggests that hierarchical textures have a higher Leidenfrost temperature compared to single-length-scale textures, which is confirmed experimentally. (C) 2013 AIP Publishing LLC.