Bio-inspired material to harvest water from thin air

Harvard scientists have designed a new material inspired by organisms such as cacti, pitcher plants and desert beetles that can effectively harvest water from thin air.
The research is the first step towards developing a system that can efficiently collect water and guide it to a reservoir, researchers said.
Certain organisms can survive in arid environments because they have evolved mechanisms to collect water from thin air.
The Namib desert beetle, for example, collects water droplets on the bumps of its shell while V-shaped cactus spines guide droplets to the plant's body.
Researchers from the Harvard University have drawn inspiration from these organisms to develop a better way to promote and transport condensed water droplets.

As the planet grows drier, researchers are looking to nature for more effective ways to pull water from air.

"Our research shows that a complex bio-inspired approach, in which we marry multiple biological species to come up with non-trivial designs for highly efficient materials with unprecedented properties, is a new, promising direction in biomimetics," said Joanna Aizenberg from Harvard.
The system is inspired by the bumpy shell of desert beetles, the asymmetric structure of cactus spines and slippery surfaces of pitcher plants.
The material harnesses the power of these natural systems, and Slippery Liquid-Infused Porous Surfaces (SLIPS) technology, to collect and direct the flow of condensed water droplets.

The major challenges in harvesting atmospheric water are controlling the size of the droplets, speed in which they form and the direction in which they flow.
For years, researchers focused on the hybrid chemistry of the beetle's bumps - a hydrophilic top with hydrophobic surroundings - to explain how the beetle attracted water.
However, researchers took inspiration from a different possibility - that convex bumps themselves also might be able to harvest water.
"We experimentally found that the geometry of bumps alone could facilitate condensation," said first author Kyoo-Chul Park, a postdoctoral researcher at Harvard.
"By optimising that bump shape through detailed theoretical modelling and combining it with the asymmetry of cactus spines and the nearly friction-free coatings of pitcher plants, we were able to design a material that can collect and transport a greater volume of water in a short time compared to other surfaces," Park said.

"Without one of those parameters, the whole system would not work synergistically to promote both the growth and accelerated directional transport of even small, fast condensing droplets," said Park.
The study was published in the journal Nature.