Inhibiting the Leidenfrost effect above 1,000 °C for sustained thermal cooling.

The Leidenfrost effect, namely the levitation of drops on hot solids 1 , is known to deteriorate heat transfer at high temperature 2 . The Leidenfrost point can be elevated by texturing materials to favour the solid-liquid contact 2-10 and by arranging channels at the surface to decouple the wetting phenomena from the vapour dynamics 3 . However, maximizing both the Leidenfrost point and thermal cooling across a wide range of temperatures can be mutually exclusive 3,7,8 . Here we report a rational design of structured thermal armours that inhibit the Leidenfrost effect up to 1,150 °C, that is, 600 °C more than previously attained, yet preserving heat transfer. Our design consists of steel pillars serving as thermal bridges, an embedded insulating membrane that wicks and spreads the liquid and U-shaped channels for vapour evacuation. The coexistence of materials with contrasting thermal and geometrical properties cooperatively transforms normally uniform temperatures into non-uniform ones, generates lateral wicking at all temperatures and enhances thermal cooling. Structured thermal armours are limited only by their melting point, rather than by a failure in the design. The material can be made flexible, and thus attached to substrates otherwise challenging to structure. Our strategy holds the potential to enable the implementation of efficient water cooling at ultra-high solid temperatures, which is, to date, an uncharted property.