GUWAHATI: Researchers at the Indian Institute of Technology Guwahati (IIT-G) have developed a method to efficiently harvest water from humid air.
A research team led by Uttam Manna, associate professor, chemistry department and Centre of Nanotechnology, IIT-G, along with his research scholars, Kousik Maji, Avijit Das and Manideepa Dhar, published the results of the path-breaking work in the journal of The Royal Society of Chemistry, a statement issued here on Tuesday said.
The team used the concept of chemically patterned SLIPS (‘Slippery Liquid-Infused Porous Surface(s)’, for the first time, to effectively harvest water from moist air.
“The researchers produced a patterned hydrophilic SLIP by spraying a sponge-like porous polymeric material on top of a simple A4 printer paper,” the statement said.
“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,” it said.
“We have produced a highly efficient water harvesting interface where the fog collecting rate is as high as 4400±190 mg/cm2/h”, Manna, the lead researcher, said.
Amid increasing water scarcity, scientists across the globe have turned to nature to design ways of water harvesting.
For example, in regions with scanty rainfall, plants and insects have devised ingenious strategies to pull and collect water out of air. Replicating this, 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 material”, explains Manna.
The concept of hydrophobicity can be understood by looking at the lotus leaf, which 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, which has a slippery surface causing 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 SLIPS to improve the water harvesting performance.
“The researchers have also compared the performance of their pitcher-plant-inspired SLIPS material to other bio-inspired ideas and have found theirs to be superior in terms of efficiency of water harvesting.
With more than 50 per cent of India’s population having no access to safe drinking water and about 200,000 people dying every year owing to lack of access to safe water, this inexpensive method for harvesting water from water vapour or fog droplets in air can potentially alleviate the water scarcity issues in the country.