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Leidenfrost sublimation engine

When a droplet is put on a heated surface it evaporates and eventually boils, but what if the surface temperature is much higher than the boiling point of water?

Click to see Leidenfrost Engine with droplets of water and disks of dry ice.

Our experiments use a hot turbine-like substrate to instantaneously vaporise a surface layer of water when a droplet touches it. This levitates a droplet on a cushion of its own vapour. The turbine-like surface shape rectifies the direction of flow of the vapour and causes a droplet to rotate. The rotation of the droplet can be used to couple the rotation of a solid. Alternatively, a disk of solid dry ice can be placed directly onto the turbine-like surface and a thin layer of solid dry ice will directly sublimate to vapour. We have used this to create the first example of a sublimation heat engine.


G.G. Wells, R.L. Aguilar, G. McHale and K. Sefiane,
A sublimation heat engine,
Nature Communications 6 (2015) art. 6390. View open access version

R.L. Aguilar,
How energy from dry ice could power human colonies on Mars,
The Conversation Online 3rd March 2015.