I had never heard of the Leidenfrost effect before, but I must say it is kind of cool (well hot actually). It is basically this, when a liquid comes in contact with something that is significantly hotter than its boiling point, it produces an insulating vapor. This vapor barrier keeps the liquid from getting hot and boiling. Usually as a liquid boils it bubbles off in all directions. However, because of the Leidenfrost effect and surface tension, the liquid can stay on (actually floating just above) the hot surface for much longer than usual. The folks at the University of Bath used this effect and a set of etched saw tooth patterns to make water move in a certain direction. Using this, they can get water droplets to actually move up hill. They created a track that uses this effect to guide water droplets around a course. It makes me think the whole thing is a sort of Escher drawing where water magically circulates around a closed track. Check out the video below.
The same effect was used by the Mythbusters to allow them to do something really crazy in the video below. They dunked their hand into molten lead. No, really... molten lead. Quite bizarre and interesting.
oh... and kids... this probably isn't something to try at home.
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