Extracting Liquid Assets From Thin Air

Over seventy percent of the Earth’s surface may be covered in water, but even still, clean drinking water is hard to come by for billions of people. In many regions, severe water shortages force people to rely on contaminated supplies, or travel long distances for this basic necessity. This daily struggle not only poses serious health risks but also hinders economic development, highlighting the urgent need for more sustainable water management practices and infrastructure improvements where water is scarce.

Engineers at MIT have thrown their hat in the ring with a novel solution to the problem that extracts water from the air. You may be thinking that this sounds an awful lot like a dehumidifier, which is hardly a new technology. But traditional dehumidifier technologies require energy for operation, which is often unavailable where clean water is scarce. So the team developed a novel solution that requires no energy, but that can still extract large amounts of water from the atmosphere.

Their system is a passive atmospheric water harvester — a vertical, window-sized panel that draws moisture from the air using a specially engineered hydrogel material. This hydrogel resembles black bubble wrap, with dome-shaped structures that swell as they absorb water vapor. As the sun heats the panel, the captured moisture evaporates and condenses on a glass surface, which is coated with a cooling layer to encourage condensation. The collected water then trickles down into a collection tube, ready to drink.

The unique composition of the device’s hydrogel is critical to its operation. Traditional hydrogels often incorporate salts like lithium chloride to improve water absorption, but these can leach into the collected water, making it unsafe to drink. To solve this, the researchers added glycerol, a compound that stabilizes the salt and prevents it from leaking out. The resulting water meets safe drinking standards, with lithium ion concentrations well below harmful thresholds.

In addition to the clever choice of materials, the device also features some simple but effective design enhancements. The hydrogel domes increase the surface area, enabling greater moisture absorption, and a polymer-coated glass chamber helps cool the surface and improves the condensation process. Altogether, the system demonstrates impressive adaptability across a wide humidity range (from 21 to 88 percent) making it viable in everything from desert to tropical climates.

The team tested their prototype in Death Valley, California, one of the harshest environments on the continent. Despite the area’s low humidity, the device consistently pulled water from the air, producing up to 161.5 milliliters per day. Although that is only about two-thirds of a cup, scaling the design into an array of panels could provide enough water to meet daily drinking needs for an entire household, even in extremely dry environments.

At present, the work is in the proof-of-concept stage, but the team envisions a future where arrays of these vertical panels could be deployed in remote communities around the world, offering a scalable, low-cost way to secure one of life's most vital resources.