Researchers’ mobile platform advances water harvesting technology


Flow separation on hydrophilic reentrant SLIPS. (A) Schematic of flow separation. Due to the coarsening effect, small droplets move into the re-entry channel. At the same time, the liquid column within each reentrant channel slides due to gravity. Arrows show the direction of movement of the smaller droplets. (B) Microscopic image of flow separation. White arrows show smaller droplets moving towards the reentrant channel. Remove droplets from the surface. (C) Schematic illustration of dropwise condensation with coarsened droplets on a smooth plane. Small droplets climb up the oil meniscus and merge with larger droplets. (D) Microscope image of the coarsened droplet. Arrows show the direction of movement of the smaller droplets. (E) Surface coverage of flow separation and droplet condensation at steady state. (F) The catchment weight of the surface with flow separation and dropwise condensation. Image source: Zongqi Guo et al., Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2209662119

This summer’s catastrophic drought in the western United States and the closure of a water treatment plant in Mississippi have shown the need to find alternative ways to draw water in times of water scarcity.

One way to address water scarcity is to get water from the air. PhD. Xianming Dai, assistant professor of mechanical engineering in the Erik Jonsson School of Engineering and Computer Science at the University of Texas at Dallas, is working on a technology that would allow anyone to have an affordable, portable device that can fetch water anywhere, anytime. It is conceivable not to use external energy.

Dai and his research group recently advanced the technology by developing a new platform to speed up the harvesting process. The team demonstrated the platform in a study published online in August. 29 inches Proceedings of the National Academy of Sciences.

The platform solves a key problem in the water harvesting process: The collected water droplets form a thermal barrier that prevents further condensation, so they need to be removed from the surface as quickly as possible to make room for more water harvesting.

The UTD team solved this problem by developing a platform with a unique shape. They cut a series of mushroom-shaped channels — smaller than a human hair in diameter — into the collection surface so that a portion of the surface material hangs over each channel. If droplets collect on the surface, they are absorbed into the channel, but the mushroom-shaped design prevents water from flowing back to the original collection surface. The collected water is collected through these channels.

The key to the platform’s success is building on Dai’s previous work in 2018 to build a novel flow-separating smooth surface to capture water from fog and air. Inspired by rice leaves and pitcher plants capable of trapping and guiding water droplets, hydrophilic synovial fluid-infused porous surfaces (SLIPS) have unique water-absorbing properties that help guide water droplets into channels. The channels are also lined with SLIPS, which helps prevent liquid backwashing onto the initial collection surface.

“Surface tension moves the liquid from the collection surface into the channel, which facilitates continuous water collection,” Dai said. “The mushroom-like channels are unique because they lock the liquid inside.”

The publication marks a major achievement for the study’s first author, Dr. Zongqi Guo, who received his degree in December.

“This work is a summary of my doctoral research. We combined microfluidics, microfabrication and surface chemistry to reveal a new basis for water sustainability, flow separation,” said Guo, now a postdoctoral researcher at the University of Minnesota .

The technology has a variety of applications, including military use. “Soldiers need to be able to drink water no matter where they are,” Day said. “This requires decentralized water harvesting technology.”

Because the technology can remove moisture from the air, it can also be used in food processing and other environments where humidity needs to be controlled, he said. Dai’s team continues to improve the technology and work to make a wider impact.

PhD. Dai’s research addresses the importance of improving the well-being of all, said Joshua Summers, professor and chair of the Department of Mechanical Engineering.

“Hopefully this publication can help inspire scientific discovery and engineering of solutions that can be widely deployed where moisture should be harvested,” Summers said. “As a huge ‘Star Wars’ fan, I’m excited to see that we’re approaching the ‘moisture farm’ of Luke’s youth.”

Co-authors of the study include mechanical engineering graduate student Dylan Boylan and Ph.D. Li Shan, researcher in mechanical engineering.

‘Climbing droplets’ could improve water harvesting efficiency

More information:
Zongqi Guo et al., Hydrophilic rainwater SLIPS enables flow separation for rapid water harvesting, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2209662119

Courtesy of The University of Texas at Dallas

Citation: Researchers’ Flow Platform Advancing Water Harvesting Technology (Oct. 4, 2022) Retrieved Oct. 4, 2022 from html

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