Artificial muscles may move the machines of the future, and the only power they need is evaporating water. Researchers at Columbia University have built artificial muscles that expand and contract with changing humidity, and in the lab, they’re already powering LEDs and propelling miniature cars.
“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 his colleagues in a paper published in the journal Nature Communications. Of course, there’s a reason for that: evaporation creates pressure changes at a very small scale, but the force it produces doesn’t generally scale up very well. But Chen and his colleagues found a way to bend the rules. They attached a layer of bacterial spores to a thin plastic tape. Spores of the bacterium Bacillus subtilis expand when they’re exposed to humidity, and they contract ...
