The Leidenfrost Maze

The Leidenfrost effect is when a liquid (in this case, water) comes in contact with a surface so hot (above the liquid's boiling point) that instead of evaporating in hurry, the water droplet becomes surrounded by a layer of water vapor, which slows down the evaporation. This is how cooks use water droplets to see hot hot a griddle is. In essence, the water droplet is hovering over the hot surface. This hovering droplet can be manipulated: for instance, when the hot surface is textured in a certain way, the drop will skitter in a predetermined direction.

Carmen Cheng and Matthew Guy used that principle to build a maze in which water droplets were directed along a winding path by the Leidenfrost effect. They use this maze to demonstrate the science, but it looks darn cool, too! (via Arbroath)