Hydrogels Make Headway: Pulling Water Out of Thin Air

By Kelley Northam

Clean water is as essential as it is precious to our health, hygiene, and habitat. However, over two billion people live in areas with inadequate water supplies. And, with climate change contributing, half of the global population could face water scarcity issues as early as 2025.

Two of the easiest ways to combat the water crisis are turning off the faucet while brushing your teeth and only running the dishwasher when it’s full. After all, you can’t pull water out of thin air.

Or can you?

Massachusetts Institute of Technology (MIT) mechanical engineer Carlos Díaz-Marín and his team have shown that you can actually get water out of thin air with the help of hydrogels.

A Salty Solution

Hydrogels can absorb and house water and are made of meshed polymers—smaller units chemically bonded together to form larger molecules. While hydrogels are not new, Díaz-Marín and his team expanded hydrogel research by publishing their findings on hygroscopic hydrogel absorbency in the journal Advanced Materials.

The team began their experiment by creating a hydrogel tube made from polyacrylamide, a polymer comprised of long, threadlike materials. Then, they sliced the tubes into thin disks and submerged them in containers of water, each with different lithium chloride salt concentrations. Lithium chloride was chosen because it can absorb more than ten times its mass in moisture.

While similar tests had only soaked hydrogels for a few days, researchers soaked these hydrogels for 30 days and found that the hydrogels absorbed and retained 24 grams of salt per gram of polymer—four times more than past studies. This salt uptick also allowed the hydrogels to pull more water from the air than previous experiments.

The researchers continued the experiment by using the salty hydrogels to absorb moisture from the air at various levels of humidity. They discovered that the hydrogels performed this task without leaking at 30, 50, and 70 percent relative humidity. This is particularly significant given that 30 percent relative humidity is lower than typical nighttime desert humidity levels.

A Pool of Possibilities

These results point to new hydrogel applications and innovative ways to combat the water crisis. Díaz-Marín and his team are now developing a hydrogel-powered device capable of harvesting vapors to generate drinking water, even in deserts and drought-prone areas. This device could extract two to five liters of water per day, supplying an average person’s daily water intake.

While we can all do our part by consciously conserving water, researchers like Díaz-Marín are finding new ways to conserve and create water to help turn the tide and save lives worldwide.