"The invention involves two electrodes and a thin layer of material, which must be covered with tiny holes less than 100 nanometers in diameter—thinner than one-thousandth the width of a human hair, according to a statement from the University of Massachusetts, Amherst, where the researchers work.

As water molecules pass through the device, from an upper chamber to a lower chamber, they knock against the tiny holes’ edges, creating an electric charge imbalance between the layered chambers. In effect, it makes the device run like a battery. The whole process resembles the way clouds make electricity, which we see in the form of lightning bolts." https://www.smithsonianmag.com/smart-news/this-new-device-ge...