This is not a paper chain, but a 3D printed material that absorbs seawater and purifies it into salt-free water. Credit: ACS Energy Letters 2025, adaptation from doi: 10.1021/acsenergylett.5C01233
Most of the Earth’s water is in the ocean and is salty to drink. Desalinated plants can drink seawater, but require a large amount of energy. Researchers reporting in ACS Energy Letters have developed sponge-like materials with long microscopic air pockets that use sunlight and a simple plastic cover to turn saltwater into freshwater.
Outdoor proof-of-concept tests successfully produced drinking water in natural sunlight, heading towards low-energy sustainable desalination.
This is not the first time scientists have created a sponge-like material that is used as a sustainable energy source for washing or desorption of water. For example, when polymers tested flafa-inspired hydrogels with polymers in their pores with chromium contaminated water and heated them in the sun, the hydrogels quickly released clean water vapor that could be collected by evaporation.
However, while hydrogels are high and filled with liquids, aerogels are harder and contain solid pores that can transport liquid water and water vapor. Aerogels have been tested as a means of desalination, but are limited by their evaporation performance and decrease as material size increases. Therefore, Xi Shen and colleagues wanted to design porous desalinated aerogels that remained efficient in various sizes.
Researchers were able to create a paste containing carbon nanotubes and cellulose nanofibers, 3D printed it on the frozen surface, allowing each layer to be solidified before the next layer was added. This process formed a sponge-like material with small vertical holes about 20 micrometers wide each.
They tested square pieces of material, ranging from 0.4 inches (1 cm) wide to about 3 inches (8 cm) wide, and found that smaller pieces release water by evaporating as efficiently as smaller ones.
A custom-made setup removes salt from the seawater in natural sunlight using a seawater beaker, black aerogels, and curved plastic caps that drip into the funnel and beaker. Credit: ACS Energy Letters 2025, adaptation from doi: 10.1021/acsenergylett.5C01233
In outdoor testing, researchers placed the material in a cup containing seawater and covered with a curved, clear plastic cover. The sunlight heated the top of the spongy material, evaporating only water, not salt, into water vapor.
The steam was collected as a liquid on a plastic cover, and now clean water was moved to the edge, where it dripped into the funnel and container under the cup. After six hours in natural sunlight, the system produced about three glasses of drinking water.
“Our aerogels allow for full desalination of any size,” Shen says.
Details: Additive frozen print aerogels for scalable desalination, size-independent vapor diffusion enabled by ACS Energy Characters (2025). doi: 10.1021/acsenergylett.5C01233
Provided by the American Chemical Society
Quote: Sponge Material and Sun Power Retrieved Salt from Sea Water (July 2, 2025), July 3, 2025 from https://techxplore.com/news/2025-07-spongy-material-sun-salt.html
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