The technology makes use of the property of bacterial spores, which are like seeds that can germinate into a living microbe under the right conditions. Absent those conditions, however, they are rather good at absorbing water whenever they find it. During absorption they swell and when they lose the water they contract, and they can do this repeatedly, without much wear and tear.
http://qz.com/429309/these-machines-can-capture-a-new-source-of-clean-energy-evaporating-water/