By Hamish Johnston
In this fantastic video, physics students at the University of Bath in the UK have had some fun with the Leidenfrost effect. This occurs when a liquid drop comes in contact with a hot surface that produces an insulating layer of vapour that keeps the drop from evaporating rapidly. This layer also allows the drop to glide effortlessly over the surface – and that’s where the fun begins.
It turns out that if you replace a smooth surface with the sort of asymmetrical teeth found in a ratchet, the drop will move rapidly in one direction. By using ratchet surfaces to accelerate liquid drops, the team has made the drops move uphill and even follow a predetermined path through a maze.
And if you wonder what would happen if you combined the Leidenfrost effect with the paramagnetic response of a liquid, check out the beautiful image in the article “Levitating drops controlled by fridge magnets”.