By Donna Lu
H.M. Cao at University of Rochester
A black panel of aluminium crafted by lasers can purify water when heated by ordinary sunlight. It could eventually be used in drought-stricken areas or regions where clean drinking water is not readily available.
Chunlei Guo at the University of Rochester in New York and his colleagues made the panel using short-pulse lasers on an 3 by 3 centimetre aluminium sheet, creating rows of tube-like microscopic grooves on the surface of the aluminium. On these grooves there are even smaller nanoscale bumps.
The resulting sheet is both black in appearance and attracts water. “If I put a sample [of the aluminium] vertically and put a drop of water on the bottom of the sample, the water will flow uphill against gravity,” says Guo.
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When one end of the panel is placed in dirty water, it draws a thin layer of water upwards, which is then evaporated in the sun. By placing the panel inside a glass box, the team collected the evaporated water for use, separating it from the dirty water with a layer of insulation.
Because of the sheet’s water-wicking abilities, it works regardless of how it is angled, so it can be oriented to always face the direction of the sun.
The team were able to purify water containing heavy metals, detergents and human waste to levels better than the contaminants standards set by the World Health Organisation and US Environmental Protection Agency for drinkable water.
It took 2 hour to obtain around 5 millilitres of purified water, so the team would like to scale up the process to purify greater volumes, and also aim to improve the method’s efficiency by making double-sided panels.
Journal reference: Nature Sustainability, DOI: 10.1038/s41893-020-0566-x
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