GUWAHATI, Dec 8 - A team of researchers at the Indian Institute of Technology Guwahati (IIT-G) have developed an efficient method to harvest drinking water from air.
Results of this work, undertaken by the research team led by Dr Uttam Manna, Associate Professor in the Department of Chemistry and Centre of Nanotechnology, IIT-G, have been published in the journal of The Royal Society of Chemistry. His team includes research scholars Kousik Maji, Avijit Das and Manideepa Dhar.
�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. For example, in regions of the world with naturally scanty rainfall, plants and insects have devised ingenious strategies to pull and collect water right out of the air. Mimicking this, scientists worldwide are trying to build technologies that can pull out water from thin air, both literally and figuratively,� said Dr Manna.
He added, �Such water harvesting techniques use the concept of hydrophobicity or water-repelling nature of some materials. 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.�
Dr Manna, however, added that 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 that causes insects that land on it to fall into its tube-shaped structure, to be digested.
The IIT-G research team has used the concept of chemically patterned Slippery Liquid-Infused Porous Surface (SLIPS) for the first time to effectively harvest water from moist air. The researchers produced a patterned hydrophilic SLIPS 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,� said the research team leader.
He added, �We have produced a highly efficient water harvesting interface where the fog collecting rate is very high.�
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.
�Given that more than 50 per cent of India�s population have no access to safe drinking water and around 2,00,000 people die every year due to lack of access to safe water, the inexpensive method for harvesting water from water vapour or fog droplets in air can potentially alleviate the water scarcity issues in the country. Apart from water harvesting, SLIPS could be used for other purposes, such as in easily cleanable household appliances, in underwater hulls of ships and submarines to prevent bio-fouling and on anti-icing windows for aircraft,� said Dr Manna.
