The innovation employs only light and air and completes the work in just six hours.

Chinese scientists have invented a clever way to turn seawater into drinkable water using nothing more than sunlight and a special sponge-like material.

This innovation, accepted for publication in the journal ACS Energy Letters, could help provide clean water in areas where it’s scarce — without relying on expensive or energy-hungry desalination plants, the inventors said in a press release.

Even though most of the Earth is covered in water, almost all of it is salty ocean liquid that we can’t drink. Desalination — the process of removing salt — is already used in many parts of the world. But the traditional desalination method is done at large plants, is expensive, and use a lot of energy.

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To tackle this challenge, the researchers, who work for the Department of Aeronautical and Aviation Engineering, and the Hong Kong Polytechnic University, created a new kind of material called an aerogel.

It’s light, full of tiny air pockets, and powered by the sun.

How it works

Unlike other water-purifying materials like squishy hydrogels, this aerogel is more rigid and has solid pores that are ideal for moving water vapor.

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Here’s what the researchers did:

• They made a special paste from carbon nanotubes and cellulose nanofibers (a material from plants).

• Using 3D printing, they built the material layer by layer on a frozen surface, creating tiny vertical channels — each only about 20 micrometers wide (roughly a quarter of a human hair).

• These channels help carry heat and water vapor efficiently.

The result is a sponge-like material that looks simple, but performs incredibly well.

To test it, the team placed a square of the aerogel into a cup of seawater. They then covered the cup with a curved piece of clear plastic. During the process, sunlight heated the top of the aerogel. The heat caused only the water to evaporate — the salt remained behind.

Then the clean water vapor rises and condenses on the underside of the plastic cover. The liquid drips down into a collection container.
After just six hours in natural sunlight, the system produced around three tablespoons of clean, drinkable water.

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While that might not sound like much, the key takeaway is that this system works at any size. Whether you use a small or large piece of the material, it maintains the same efficiency — making it easy to scale up for real-world use.

Why it matters

This technology is energy-free as no electricity is needed; simple to set up — just a sponge and sunlight; and scalable — it works for small or large systems.

As the global population grows and fresh water becomes harder to access, innovations like this sun-powered sponge could make a big difference — especially in remote or under-resourced areas.