Don’t you hate it when your phone battery dies? In the future, you might be able to recharge your gadget by breathing on it, thanks to a technique that harvests electricity from moisture in the air.

Water droplets might seem an unlikely source of energy, but then can hold a form of static electricity called hygroelectricity , which is thought to be the source of electric charge that causes lightning. This charge can be transferred from droplets to other tiny particles, such as dust. …