Water makes up over 70 percent of Earth's surface, and the water cycle is constantly churning all around us. There's an immense amount of power in this process, but thus far few technologies have been developed capable of harnessing this clean, renewable, bountiful resource.

Researchers at Columbia University are hoping to change that. They have invented a novel new type of engine that is powered entirely by evaporating water, reports Discover. The device works by integrating biological spores which can expand or contract like muscles when exposed to different levels of moisture.

“Engineered systems rarely, if ever, use evaporation as a source of energy, despite myriad examples of such adaptations in the biological world,” wrote lead author Xi Chen and colleagues in a paper recently published in the journal Nature Communications.

The power generated by evaporation is difficult to capture because, though it is happening all around us constantly, it creates pressure changes at a very small scale. But the researchers discovered an ingenious way of harnessing it, by enlisting spores from the bacterium Bacillus subtilis.

Because these spores store water in very small, nanometer-scale spaces, they respond dramatically to pressure changes caused by evaporating moisture. They expand when exposed to humidity, and contract as they dry out — a process that can be compared to how muscles operate.

So Chen and colleagues wondered if they could drive an engine using collections of these spores as their muscles, and with evaporating water as the input. The idea resulted in two enterprising inventions: an electric generator capable of powering a pair of LED lights, and a miniature toy "car" that seemingly moves with miraculous efficiency.

You may have to see these inventions in action to get the full grasp of just how innovative they are. Luckily, there's a video for that here:

Researchers hope that their work could eventually be upscaled for other larger applications. For instance, the basic principle here could be used to build power plants over bodies of water that generate electricity as the water evaporates. And since the materials used to make the evaporation engine are relatively cheap, the technology could be particularly useful in regions that don't have access to typical electrical infrastructures.

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