IIT Guwahati developing method to ‘harvest’ drinking water from air

Researchers at Indian Institute of Technology Guwahati (IIT-G) on Tuesday said its researchers have developed novel materials that can efficiently harvest water from humid air.

With increasing water scarcity throughout the world, there have been attempts to collect and conserve water through non-traditional means. Scientists have turned to nature to design ways of water harvesting.

Scientists worldwide are trying to build technologies that can pull out water from thin air, both literally and figuratively.

“Such water-harvesting techniques use the concept of hydrophobicity or water-repelling nature of some materials,” Uttam Manna, Associate Professor, Chemistry department and Centre of Nanotechnology, IIT Guwahati, said in a statement.

The concept of hydrophobicity can be understood by looking at the lotus leaf. The lotus leaf is water repellent because there is a layer of trapped air between the leaf surface and the water droplet, which causes the droplet to slide off the leaf.

However, simple hydrophobicity such as this is unsuitable for water harvesting from highly humid environments because high moisture content can displace the trapped air and cause permanent damage.

Instead, researchers mimic the pitcher plant, an ‘insect-eating’ plant, that has a slippery surface that causes insects that land on it to fall into its tube-shaped structure, to be digested.

“In the past geometries of Rice leaves and cacti are associated with ‘Slippery Liquid-Infused Porous Surface(s)’ or SLIPS to improve the water harvesting performance,” the researchers wrote.

According to the study, published in the journal of The Royal Society of Chemistry, the research team has used the concept of chemically patterned SLIPS for the first time, to effectively harvest water from moist air.

They produced a patterned hydrophilic SLIP by spraying a sponge-like porous polymeric material on top of a simple A4 printer paper.

Further, chemically modulated hydrophilic spots were associated on the coating prior to lubricating with two distinct types of oils – natural olive oil and synthetic krytox.

This surface could harvest water from foggy/water vapour laden air without the need for any cooling arrangement.

“We have produced a highly efficient water harvesting interface where the fog collecting rate is as high,” Manna said.

The researchers have also compared the performance of their pitcher-plant inspired SLIPS materials to other bio-inspired ideas and have found theirs to be superior in terms of efficiency of water harvesting.

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