The majority of Earth’s water is unfit for human consumption since it is trapped in salty oceans. Although desalination plants are capable of turning saltwater into freshwater, they usually use a lot of energy. Scientists have now created a novel, sponge-like substance that effectively turns saltwater into drinkable water when combined with sunlight and a basic plastic cover. Their research, which was published in ACS Energy Letters, shows that an outdoor proof-of-concept that used just natural sunlight to successfully produce drinkable water is a potential step towards sustainable, low-energy desalination.

Despite initially looking like a paper chain, this novel substance is actually a 3D-printed structure designed to absorb and cleanse seawater.

Previous Innovations in Sunlight-Driven Purification

In the past, scientists have developed spongy materials that are powered by sunlight to purify or desalinate water. For example, a loofah-inspired hydrogel treated chromium-contaminated water by producing clean water vapour using sun-heated polymers. Aerogels have solid, porous structures that may transfer water or vapour, making them more stiff than hydrogels, which are soft and filled with liquid. Although aerogels have been investigated for desalination as well, their effectiveness typically decreases with increasing material size.

In order to get over this restriction, Xi Shen and his group created a porous aerogel that works reliably at any size.

Carbon nanotubes and cellulose nanofibers were combined to make a paste, which they then 3D printed layer by layer on a frozen surface, letting each layer set before adding the next. This technique created an aerogel that resembled a sponge and had consistent vertical microchannels that were around 20 micrometres wide. The larger pieces had similar evaporation ability to the smaller ones were tested in squares that ranged in size from 1 to 8 centimetres wide.

Real-World Testing and Results

In an actual outdoor experiment, the scientists submerged the aerogel in a cup of seawater and sealed it with a clear, curved plastic lid. Only the water, not the salt, evaporated as a result of the material’s surface being heated by sunlight. After condensing on the lid, the resultant vapour trickled down into a collecting container and a funnel. Approximately three tablespoons of drinking water were produced by the system after six hours of exposure to natural sunlight.

“Our aerogel allows full-capacity desalination at any size,” Shen says, “which provides a simple, scalable solution for energy-free desalination to produce clean water.”

The Hong Kong Polytechnic University, the Environment and Conservation Fund of Hong Kong SAR, the Research Grants Council of Hong Kong SAR, and the National Natural Science Foundation of China all provided funding for the study.

Established in 1876, the American Chemical Society (ACS) is a nonprofit organisation whose mission is to promote chemistry and scientific understanding globally. Although it doesn’t carry out research itself, it sponsors scientific conferences, publishes highly cited peer-reviewed publications, and provides research tools through its CAS section. The headquarters of ACS are located in Columbus, Ohio, and Washington, D.C.

Original Publication
Authors: Xiaomeng Zhao, Yunfei Yang, Xuemin Yin, Zhuo Luo, Kit-Ying Chan and Xi Shen.
Journal: ACS Energy Letters
DOI: 10.1021/acsenergylett.5c01233
Article Title: “Size-Insensitive Vapor Diffusion Enabled by Additive Freeze-Printed Aerogels for Scalable Desalination”
Article Publication Date: 2-Jul-2025