Harvesting drinking water by making it jump out of foggy air sounds far-fetched, but that is exactly what is achieved by some clever chemistry inspired by the water-gathering exoskeletons of desert beetles.
Research published in the journal RSC Advances reveals how surface coatings with water-attracting and water-repelling regions make water droplets form and jump together into larger droplets that can be collected. The system offers an inexpensive and efficient route to condensing much-needed drinking water from air in arid and semi-arid regions of the world.
Xikui Wang and Youfa Zhang and their colleagues at Southeast University in Nanjing, China, took inspiration from the bumpy surfaces of desert beetles to develop their new technology. The bumps on the beetle’s back promote the formation of water droplets from foggy air. The water is then channelled into the beetle’s mouth, allowing it to survive in the dry wilderness of South West Africa.
To adapt the beetle’s trick for human use, the researchers built a hybrid material by adding silicon carbide particles to a superhydrophobic silicon dioxide coating on aluminium sheets. This created a rough surface with interspersed and interacting water-attracting and water-repelling regions that encouraged tiny water droplets to form.
The water-gathering power of the beetles was then improved by bringing two layers of the synthetic material close together. Remarkably, the forces on the smallest droplets made them jump off the surface and collide. This makes the system more than twice as effective at catching water from the air as single surfaces alone.
Other methods for harvesting water from air do already exist, but the researchers say the new process is easier and will cost less.
While their proof-of-concept work paves the way for building better watercollectors, they also see possible applications for desalination systems to extract drinking water from the sea, and applications in other fields involving heat exchange and water purification.
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Article details:
Beetle-like droplet-jumping superamphiphobic coatings for enhancing fog collection of sheet arrays
Xikui Wang, Jia Zeng, Xinquan Yu, Caihua Liang and Youfa Zhang
RSC Advances, 2020, 10, 282-288
DOI: 10.1039/c9ra09329j
