Dancing water droplets could charge your phone

You're stuck on a desert island. The midday sun is beating relentlessly down on you, and vultures are circling overhead. Your water ran out hours ago, and so did the battery on your satellite phone. If only there was a way to charge it, you could call for help. And if only that device could also produce clear drinking water at the same time.

Oh wait, you totally have that device! Or at least, you might sometime in the near future.

That's because a study conducted by a research team from MIT has discovered a way to produce both water and electric charge from the moisture in the air around us.

The device was designed after the same team discovered that water droplets gain an electrical charge when they spontaneously jump away from superhydrophobic surfaces during condensation.

The team's amazing discovery is all the more amazing considering they weren't even looking for any results to do with electricity. The results came about during a fairly mundane experiment on heat transfer. The team found that by placing a metal plate close to the droplets bouncing off the superhydrophobic surface, the droplets were attracted towards it thanks to its opposite charge. This enhanced both their ability to bounce and transfer heat.

Mechanical engineers Nenad Miljkovic and Evelyn Wang published their new findings in the journal Applied Physics Letters.

A device could be created using the team's findings that generated charge from a series of interleaved metal plates. While the team used copper due to its high conductivity, any current-carrying metal could be used, including cheaper materials like aluminium.

According to Miljkovic, a cube of 50cm on each side would allow a user to fully charge an average smartphone in around 12 hours. Not the fastest thing ever, then – but it's not designed to be used around the house. This would be used primarily in developing countries or emergency situations, where regular and dependable access to electricity isn't something you can take for granted.

In practice, the system is more likely to be used to power remote environmental sensors, or other systems where power sources like solar aren't forthcoming.

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