Superhydrophobic surfaces boil water without bubbles

Nature : Normally, when water comes in contact with a very hot metal surface, a layer of water vapor is formed that keeps the water from making direct contact with the metal. When the surface cools below a certain pointâmdash;the Leidenfrost temperatureâmdash;the vapor no longer supports the water, which touches the surface and boils explosively. Engineers from the Clean Combustion Research Center at the King Abdullah University of Science and Technology in Thuwal, Saudi Arabia, led by Ivan Vakarelski, coated metal spheres with a commercial material that made the surface of the spheres rough and superhydrophobic. When they heated the spheres and submerged them in water, the layer of water vapor that was created never dissipated as the spheres cooled. A test with the same material coating metal cylinders that were heated from within resulted in the cylinders reaching 250 °C, while untreated ones reached only 106 °C. The vapor layer formed by the uncoated metal was unstable and allowed liquid water to contact the metal and boil away, thus keeping the cylinder cool.