The researchers’ one-of-a-kind platform solves a critical issue in water harvesting: Collected water droplets act as a thermal barrier, preventing further condensation, so they must be removed from the surface as soon as possible to make room for more harvesting.
The team solved this issue by creating a platform with a distinct shape. They cut a series of mushroom-like channels into the collection surface, each one smaller in diameter than a human hair, so that some of the surface material overhangs each channel. Droplets that collect on the surface are absorbed into the channels, but the mushroom design prevents the water from returning to the initial collection surface. Water is collected through these channels.
The megadrought in the Western United States this summer, as well as the failure of a Mississippi water treatment plant, have highlighted the need for alternative water access during shortages.
Harvesting water from the air is one solution to water scarcity. Dr. Xianming “Simon” Dai, assistant professor of mechanical engineering in The University of Texas at Dallas’ Erik Jonsson School of Engineering and Computer Science, is developing technology that will allow anyone to have an affordable, portable device that can access water anywhere, at any time, and with no external energy.
The surface tension force moves the liquid from the collection surface into the channel, which is beneficial for continuous water harvesting. The mushroom-like channels are unique in that they contain the liquid.
Dr. Xianming Simon Dai
Dai and his team of researchers recently advanced that technology by developing a novel platform to accelerate the harvesting process. The team demonstrated the platform in a study published online Aug. 29 in Proceedings of the National Academy of Sciences.
The platform solves a key problem in water harvesting: Collected water droplets form a thermal barrier that prevents further condensation, so they need to be removed from the surface as rapidly as possible to make room for more harvesting.
The UTD team addressed this problem by developing a platform with a unique shape. They cut a series of mushroom-like channels – smaller in diameter than a human hair – into the collection surface so that part of the surface material overhangs each channel. As droplets collect on the surface, they are absorbed into the channels, but the mushroom design prevents the water from flowing back onto the initial collection surface. Harvested water is collected through those channels.
A novel flow-separation slippery surface built on the foundation of Dai’s prior work in 2018 to capture water from fog and air is critical to the platform’s success. The hydrophilic slippery liquid-infused porous surface (SLIPS), inspired by rice leaves and pitcher plants that can trap and direct water droplets, has a unique water-absorbing property that helps direct water droplets into the channels. SLIPS are also used to line the channels, which prevents liquid from backwashing onto the initial collection surface.
“The surface tension force moves the liquid from the collection surface into the channel, which is beneficial for continuous water harvesting,” Dai explained. “The mushroom-like channels are unique in that they contain the liquid.”
The publication marked a major achievement for Zongqi Guo PhD’21, first author of the study, who earned his degree in December.
“This work is a summary of my PhD research. We combined microfluidics, microfabrication and surface chemistry to unveil the new fundamentals for water sustainability, which is flow separation,” said Guo, now a postdoctoral fellow at the University of Minnesota.
The technology has a variety of applications, including military uses. Dai received an Army Research Office Young Investigator Program award in 2019 to advance the research, which is also funded by the National Science Foundation.
“Soldiers need to be able to drink water wherever they are,” Dai said. “This requires a decentralized water harvesting technology.”
Because the technology removes moisture from air, it also could be useful in food processing and other environments that require humidity control, he said. Dai’s team continues to improve the technology and work toward making broader impacts.
Dai’s research, according to Dr. Joshua Summers, professor and department head of mechanical engineering, addresses the importance of improving the welfare of all people.
Summers hopes that “this publication will help stimulate the scientific discovery and engineering of solutions that can be widely deployed where moisture should be harvested.” “As a huge ‘Star Wars’ fan, I am thrilled to see that we are getting closer to Luke’s childhood’moisture farms.'”
Dylan Boylan, a mechanical engineering graduate student, and Dr. Li Shan, a mechanical engineering research associate, are among the study’s co-authors.
