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In zones like the Atacama, where winds bring fog but no rain, the invention of trap in the 1960s which can absorb that damp from the air has helped sustain settlements otherwise suffering from drought.

Fog traps are polymer-mesh (聚合物网) screens in metal frames. As misty air blows through them, drops of water get stuck to the mesh. Those absorb others until the result breaks free and runs down the screen, as a raindrop runs down a window glass, into a collector. A typical trap, with a 40-square-metre collecting area, produces about 200 liters a day. That is enough to supply around 60 people with drinking water. Such a collector costs $1,000 or so, and will last a decade.

A simple idea, then. But even simple technology can be upgraded. And that is exactly what Urszula Stachewicz of the AGH University of Science and Technology, in Krakow, Poland, proposes to do.

Her upgrade relies on giving the mesh a slight electrical charge. The outside of each thread in a mesh might be given one electrical polarity (极性) while the other polarity might be buried inside the thread. Just as static electricity (静电) will attract a balloon to a wall, a surface charge created in this way will attract small water drops from the air.

Previous attempts to do this have coated the threads with metal. But that is expensive. As they describe in ACS Namo, Dr. Stachewicz and her student Daniel Ura have done it by changing the way the threads work, which is cheap.

Dr. Stachewicz and Mr. Ura proposed to use a technique called electrospinning and they kept experimenting, which resulted in meshes able to collect 50% more water than commercial versions, at no extra cost of production. They expect soon to have a practical version which can be made available for sale. And that will certainly improve the lives of people who rely for their survival on drawing water not from a well, but from thin air.