Levitating Droplets Emit Blue Light as They Float on a Cushion of Plasma

Levitation may seem like something out of science fiction, but it's exactly what researchers are aiming for in a new study. They've discovered a new way to levitate liquid droplets while, at the same time, creating a mini light show, causing the droplet to spark as it floats.

The floating effect is actually similar to Leidenfrost levitation. This is when droplets dance on a hot vapor cushion. For example, you've probably seen this effect when pouring some water on a hot frying pan. In this case, though, the researchers created the vapor with a strong jolt of electricity instead of heat, ionizing the gas into plasma that glows a soft, blue light.

"This method is probably an easy and original way to make plasma," said Cedric Poulain, one of the researchers, in a news release. In fact, the deformability of a liquid drop may allow the researchers to rig up a device to move the plasma along a surface.

The new discovery was made after researchers began an experiment to explore the limits of the analogy between the boiling phenomenon and water electrolysis, which is the breakup of water into hydrogen and oxygen gases by an electric current. The scientists wanted to see if there was a similar levitation effect, as in the case of the Leidenfrost effect, during water electrolysis.

In this latest study, the researchers devised a set-up to run electricity through droplets and then film the droplets at high speed. At about 50 volts, they found that the bottom of the droplet started sparking and then levitated as a faint blue glow emitted from the gap between the droplet and the surface.

The findings reveal a bit more about the properties of water, and show that plasma levitation is, in fact, possible.

The findings are published in the journal Applied Physics Letters.

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