Imagine if water could create energy just by existing. Ozgur Sahin, Zeca Oliveira and his team of bioengineers have discovered a way for that to be possible. And the whole engine costs maybe five dollars to make.
The little engine uses a puddle of water to power things such as a miniature car and LED lights. The energy comes from the reactions of tiny strips of plastic (called HYDRAs) that have been coated in spores. The spores are from a common grass bacteria that change shape depending on tiny changes in humidity. These same spores when applied to thin, bunches pieces of plastic can make the plastic expand and contract with those same tiny levels of humidity. So as water naturally evaporates, the humidity changes, and the HYDRAs respond.
Sahin came up with the idea more than 5 year ago while studying micro-organisms. He noticed that the spores stay rigid even though they contract and expand with the humidity. This meant that their movements were full of energy because they stayed strong.
It took many experiments with the spores to figure out how to mimic their natural response. But Sahin and his team learned a way to paint them onto the strips of plastic with laboratory glue and still have them move. The spores also have the ability to last tens or maybe hundreds of years in the wild, so there is a large probability that they will survive being part of the HYDRAs for many long years.
Sahin points out that the wind on Earth is moved primarily due to evaporation. That means that if the power of evaporation can be harnessed, much energy is to be had.