Hydrogels harvest moisture to produce clean water from air

Engineers have developed hydrogels that could tap the approximately 50,000km³ of water contained in the atmosphere, an advance that could help alleviate water crises.

Solar-Powered moisture harvester collects & cleans water from air

The breakthrough from The University of Texas at Austin is a solar-powered technology that absorbs moisture from the air and returns it as clean, usable water. The technology, which is described in Advanced Materials, relies on hydrogels, which are gel-polymer hybrid materials that can retain large amounts of water and release it on heating.

This combination has been proved to work in humid and dry weather conditions and is crucial to enabling the production of clean, safe drinking water from the air.

The research team was led by Guihua Yu in UT Austin's Cockrell School of Engineering. "We have developed a completely passive system where all you need to do is leave the hydrogel outside and it will collect water," said Fei Zhao, a postdoctoral researcher on Yu's team and co-author of the study. "The collected water will remain stored in the hydrogel until you expose it to sunlight. After about five minutes under natural sunlight, the water releases."

The current technology builds upon a 2018 breakthrough made by Yu and Zhao in which they developed a solar-powered water purification innovation using hydrogels that cleans water from any source using only solar energy.

The team's innovation is said to take that work a step further by using the water that already exists in the atmosphere. For both hydrogel-based technologies, Yu and his research team developed a way to combine materials that possess hygroscopic (water-absorbing) qualities and thermal-responsive hydrophilicity, which is the ability to release water upon heating.


"The new material is designed to…harvest moisture from the air and produce clean water under sunlight, avoiding intensive energy consumption," said Yu, an associate professor of materials science and mechanical engineering.

Prototype tests showed daily water production of up to 50l per kilogram of hydrogel.

Representing a novel strategy to improve upon atmospheric water harvesting techniques being used today, the technology could also replace core components in existing solar-powered water purification systems or other moisture-absorbing technologies.

Yu and his team have filed a patent, and Yu is working with UT's Office of Technology Commercialisation on the licensing and marketing of the hydrogels. The research was funded by the Alfred P. Sloan Foundation, the Camille & Henry Dreyfus Foundation and the US National Science Foundation.