The Leidenfrost Effect is the scientific phenomenon in which water dropped on a hot surface floats on a cloud of its own vapor, seemingly slowing the evaporation process.

When the hot surface is given a rigged, saw-tooth-like texture, the drops of water are propelled in fixed direction.

Undergraduate students Carmen Cheng and Matthew Guy at the University Of Bath took this concept to the next level by creating a Leidenfrost Maze which motivates droplets of water to correctly traverse through a set puzzle of avenues.

http://www.youtube.com/watch?feature=player_embedded&v=vPZ7sx3EwUY