CLEAN WATER FROM THE DESERT

Some parts of the world have not only limited amounts of clean drinking water,

but also low humidity, making alternative water-harvesting techniques, such as collecting rainfall or dew, impractical. But a new water-collecting device built by an Mit-based team might help. Though the device, about the size of a small pack of Post-it notes, doesn’t have a name yet, the team has already tested it successfully in Tempe, Arizona – where relative humidity in the daytime is as low as 10 per cent.

As for how it works: The device’s key feature is a thin layer of a specially engineered compound called a metalorganic framework (MOF). MOF-801 is super-porous, and pulls water molecules from the air in a process called adsorption. ‘It acts essentially like a sponge for water vapour,’ says Evelyn Wang, a professor of mechanical engineering who headed up the initial experiments. The MOF extracts vapour from the atmosphere overnight, then uses sunlight to condense the vapour into liquid, a process that’s not as easy to carry out as it sounds.

Eventually, the machines could collect about 15 litres of water per day – enough for a family of four. Measuring these modest ambitions against the estimated trillions of litres of water present in Earth’s atmosphere (and adverse climate effects) is unlikely, but Wang plans to bring in a few climate scientists to consult, just in case. She hopes to have a usable product for people afflicted by water shortages in the next three to five years.