Nature Communications

Researchers at Columbia University have created the first-ever car that uses evaporated water for power. It just happens to be a very, very tiny car:

The car is powered by the shrinking and growing of bacterial spores that change size in humidity. Ozgur Sahin—who, along with other researchers built the spore-car—discovered that the shifting spores could be used for energy last year. A press release explained the power of spores at the time:

[…]spores can take on water and almost immediately restore themselves to their original shape. Sahin realized that since they shrink reversibly, they had to be storing energy. In fact, spores would be particularly good at storing energy because they are rigid, yet still expand and contract a great deal, the researchers predicted.

To fuel the car, Sahin and his team built an artificial muscle using the spore energy. As the air becomes humid, the spore-muscle stretches, and as air escapes, the spore-muscle retracts. When the escaped air makes the atmosphere humid, the process repeats.

Nature Communications

And voila, water-powered car.

In a paper detailing the research published in Nature Communications, the authors note that they hope this opens the door for other vapor-driven device: "Due to the ubiquity of evaporation in nature and the low cost of materials involved (plastic tapes, hygroscopic materials), the engines presented here may find applications as energy sources for a wide range of off-the-grid systems that function in the environment."

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Off-the-grid systems that function in the environment don't sound quite like adult-sized cars, but we're holding out hope.

Danielle Wiener-Bronner is a news reporter.