Researchers have developed a sponge-like aerogel material to turn seawater into drinkable freshwater.
This new technology, developed by a team at the Hong Kong Polytechnic University, provides a hopeful path towards low-energy, sustainable desalination.
Interestingly, the proof-of-concept showcased promise in the real-world testing.
Material with tiny air pockets
Our planet is abundant in water. But the vast majority of it is too salty for us to use.
Because there is a limited amount of fresh water and the global population is growing, desalination – the process of removing salt from water – has become a vital technology worldwide.
A custom-made setup removes salt from seawater in natural sunlight, using a beaker of seawater, a black piece of aerogel, and a curved plastic cap that drips into a funnel and beaker. Image: ACS Energy Letters 2025.
The main drawback of conventional desalination plants is the requirement for significant energy.
Therefore, there has been a need for the development of low-energy, sustainable desalination methods to address global water scarcity challenges in an environmentally responsible way.
In this development, the team created a sponge-like material featuring 'microscopic air pockets' that can convert saltwater into freshwater.
This innovative approach uses only sunlight and a basic plastic cover, offering a simple and efficient desalination solution.
Now, you might have heard of other spongy materials for water cleaning, like hydrogels. They’re squishy and filled with liquid. But this new material is an aerogel – it is more rigid, with solid pores that are perfect for moving water vapour.
This isn’t a paper chain, it’s a 3D-printed material that soaks up seawater, purifying it into salt-free water. Image: Adapted from ACS Energy Letters 2025.
So, how did they make it?
The team led by Xi Shen and colleagues created a paste from carbon nanotubes and cellulose nanofibres.
The paste was then used in 3D printing to build it layer by layer on a frozen surface, creating those perfectly uniform, tiny vertical holes (a mere 20 micrometres wide).
Shows promise in testing
The coolest part is that the new material maintains its efficiency no matter its size.
The team tested with square pieces of the material that varied in size, ranging from a small 0.4 inches wide to three inches wide.
The evaporation rate of water remained equally efficient for both the smaller and larger pieces. This could be beneficial for scaling up the technology.
To put it to the test, researchers took it outdoors.
They placed the aerogel in a cup of seawater, covered it with a simple, curved plastic lid, and let the sun do its work.
Sunlight heats the spongy material, evaporating only the water, leaving the salt behind.
This clean water vapour then collects on the underside of the plastic cover. As it cools, it condenses back into liquid, dripping into a funnel and then into a container below.
Technique scalable
After just six hours in natural sunlight, this simple system generated about 'three tablespoons' of fresh, drinkable water. Although the amount is less, the team says the technique is scalable.
“Our aerogel allows full-capacity desalination at any size, which provides a simple, scalable solution for energy-free desalination to produce clean water,” Shen stated.
Around the globe, as many as 300 million people across 150 countries rely on desalination to meet their daily water needs.
In recent years, there have been a lot of developments in solar-powered desalination techniques. One notable tech comes from researchers who have developed a desalination system designed to operate in direct rhythm with the sun’s intensity.
The findings were detailed in the journal ACS Energy Letters.