Popular Mechanics (South Africa) - - How Your World Works -

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.

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