BBC Future

The Leidenfrost effect: When water runs uphill

By heating droplets of water, researchers can make them do strange things – from bouncing up a ramp to navigating a maze.

If you’ve ever sprinkled water onto a hot stove while cooking, you’ll know the droplets will bubble and boil away instantly.

Yet water performs a strange trick once a surface gets hotter and hotter – instead of evaporating, it will form beads and start bouncing. It’s called the Leidenfrost effect.

By heating a ridged surface, researchers at the University of Bath in the UK have exploited this trick to make water droplets run uphill.

The Earth Unplugged team explains why the Leidenfrost effect happens – and even send coloured droplets hurtling round a hot maze like tiny floating jelly beans.

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