In a pinch: MIT study says salty hydrogels can harvest water from the air

16 Jun 2023

Image: © Melica/

The discovery by MIT could provide a way for very hot climates to absorb water from the air and conserve it.

Researchers that have been looking at ways of designing new materials to cope with climate crisis-related environmental challenges have made an interesting breakthrough, creating a superabsorbent material that can soak up a record amount of moisture from the air, even in desert-like conditions.

It was made by a group of engineers from the Device Research Lab at the Massachusetts Institute of Technology (MIT), one of the best-known research hubs in the world.

They honed in on hydrogels as potential materials for absorbing moisture from the air, which could be a game changer for drought-afflicted nations that don’t have easy access to clean water.

Hydrogels are mostly made from water and polymer and they look like slippy, soft stretchy material. They are already used in nappies to absorb moisture, so scientists hypothesised that they might be effective at harvesting water from the air, too.

When they began their research inquiries into hydrogel’s abilities to absorb water from the atmosphere, they found that adding salts to the gel could make it more effective at retaining moisture. This had already been done by other scientists in the past.

The MIT group experimented with adding salt into hydrogel which produced a material that can absorb and retain water, as well as swell to accommodate more water.

“It’s the best of both worlds. The hydrogel can store a lot of water, and the salt can capture a lot of vapour. So it’s intuitive that you’d want to combine the two,” said Gustav Graeber, one of the authors of a paper on the study that was published in the journal Advanced Materials.

But they found that the type of salt and the quantity of salt used can impact the hydrogel’s efficiency at absorbing water. The team added lithium chloride – a salt – to the hydrogel, with 4-6g of salt per gram of polymer performing the best. These samples absorbed about 1.5g of vapour per gram of material in dry conditions of 30pc relative humidity.

While one of the team’s members, Carlos Díaz-Marin, said they had been “application-agnostic” in the sense that they mostly focused on the properties of the material rather than its potential uses, it could have any number of uses.

Díaz-Marin, a mechanical engineering graduate student at MIT, added that the team has now begun exploring “widely different problems like how to make air conditioning more efficient and how you can harvest water. This material, because of its low cost and high performance, has so much potential.”

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Blathnaid O’Dea was a Careers reporter at Silicon Republic until 2024.