Laser-sculpted aluminium purifies water with the power of sunlight

By Donna Lu

A black panel of aluminium crafted by lasers can purify water when heated by sunlight. It could eventually be used in drought-stricken areas or regions where clean drinking water isn’t readily available.

Chunlei Guo at the University of Rochester in New York and his colleagues made the panel using short-pulse lasers to alter the surface of a 3-centimetre square aluminium sheet. They created rows of tube-like microscopic grooves on the metal and 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 evaporates in the sun, purifying it. 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 ability, it works regardless of how it is angled, so it can be oriented to always face the sun.

The team was able to purify water containing heavy metals, detergents and human waste to levels better than the contaminants standards set by the World Health Organization and US Environmental Protection Agency for drinkable water.

It took 2 hours to obtain around 5 millilitres of purified water, so the researchers would like to scale up the process to purify greater volumes. They also aim to improve the method’s efficiency by making double-sided panels.

Journal reference: Nature Sustainability, DOI: 10.1038/s41893-020-0566-x