Today, 2.2 billion people in the world lack access to safe drinking water. But the atmosphere contains millions of billions of gallons of water in the form of vapor, and researchers have tried various strategies to capture and condense it in places where traditional sources are inaccessible. Now MIT engineers have improved on that approach with an atmospheric water harvester based on an absorbent hydrogel.
The gel they developed has more vapor-carrying capacity than some materials others have used to trap water from the air, and it is less likely to leak the salts that are often embedded in hydrogels to increase absorption. They also increased its surface area, and thus the amount of vapor it can hold, by molding it into a pattern of small domes resembling bubble wrap.
COURTESY OF THE RESEARCHERS
In the researchers’ prototype device, a half-square-meter panel of the hydrogel is enclosed in a glass chamber coated with a cooling polymer film. When the vapor captured by the textured material evaporates, the bubbles shrink down in an origami-like transformation. The vapor then condenses on the glass, where it can flow out through a tube.
The system runs entirely on its own, unlike other designs that require batteries, solar panels, or electricity from the grid. The team ran it for over a week in Death Valley, California—the driest place in North America. Even in those conditions, it squeezed clean water from the air at rates of up to 160 milliliters (about two-thirds of a cup) per day.
“We have built a meter-scale device that we hope to deploy in resource-limited regions, where even a solar cell is not very accessible,” says Professor Xuanhe Zhao, the senior author of a paper on the work. The team estimates that a small array of the panels could passively supply a household with drinking water even in a desert, with greater production in temperate and tropical climates.