Currently, around 2.2 billion people worldwide do not have access to safe drinking water. In the U.S., over 46 million individuals face water shortages, either lacking running water or relying on water that isn’t safe to drink. The demand for clean water is increasingly putting pressure on existing sources like rivers and lakes.

To tackle this issue, a team of engineers from MIT is looking to the atmosphere as a potential solution. The air around us holds a vast amount of water vapor, and if it can be captured and turned into liquid water, it could provide drinking water in areas lacking traditional sources.

In line with this vision, the MIT researchers have created and tested a new device designed to harvest water from the air, demonstrating its capability to produce safe drinking water, even in dry conditions.

This innovative apparatus resembles a black window panel and is constructed from a special water-absorbing hydrogel material housed within a glass chamber coated with a cooling layer.

The hydrogel looks like black bubble wrap. It features dome-shaped sections that expand as they soak up water vapor. When the vapor is released, the domes contract, kind of like origami folding back. The vapor then condenses on the glass and is collected through a tube as drinkable water.

What’s remarkable is that this system operates independently and doesn’t rely on batteries or electrical power, unlike other similar devices. The team tested the harvester over a week in Death Valley, California, the driest area in North America. Even under low humidity, the device successfully collected up to 160 milliliters (about two-thirds of a cup) of water daily.

The researchers believe that installing several of these vertical panels together could provide a household with continuous drinking water, even in arid desert climates. Furthermore, the device’s production of water would increase in more humid regions.

“We’ve developed a scalable solution that we can implement in areas with limited resources, where even solar panels may not be practical,” explains Xuanhe Zhao, a professor at MIT. “This technology could lead to larger installations, providing real benefits to communities in need.”

The details of this new design are discussed in a recent article published in the journal Nature Water. The main author is Will Chang Liu, a former MIT researcher now working at the National University of Singapore. The team included several MIT colleagues along with collaborators from other institutions.

Understanding Hydrogels

Hydrogels are soft materials composed mostly of water and a network of tiny polymer fibers. Zhao’s research group at MIT has explored their use in various applications, including medical coatings and flexible electrodes.

According to Zhao, hydrogels excel in absorbing moisture from the air due to their composition.

Researchers are investigating various methods to efficiently capture water vapor. So far, one of the most effective approaches involves using metal-organic frameworks (MOFs)—specialized materials that can also draw moisture from dry air. However, MOFs don’t expand when they absorb water, limiting their capacity.

Collecting Water from Air

The new hydrogel water harvester overcomes key issues faced by other designs. Some previous models have used micro- or nano-porous hydrogels, producing salty water requiring further filtration.

Salt is naturally absorbent, and some researchers have added salts like lithium chloride to hydrogels to enhance water absorption. However, this can lead to salt leaking into the water when collected.

To prevent this, the MIT team incorporated glycerol into the hydrogel, a substance that helps stabilize the salt, ensuring it remains trapped within the gel and doesn’t leak into the collected water.

Additionally, the hydrogel’s design includes a microstructure without tiny pores, further preventing salt from escaping. The salt levels in the collected water were well below acceptable limits, much lower than those found in other hydrogel-based designs.

Alongside modifying the hydrogel’s composition, the researchers improved its shape. Instead of a flat sheet, they shaped the gel into small dome patterns, similar to bubble wrap, to maximize surface area and water vapor absorption.

The team created a half-square-meter hydrogel and placed it inside a window-like glass chamber. They applied a special polymer coating on the chamber’s surface to promote cooling, which encourages water vapor evaporation from the hydrogel, allowing it to condense on the glass. They set up a simple tubing system to collect the water as it dripped down.

In November 2023, they field-tested the device in Death Valley. Over a week, they monitored how effectively the hydrogel absorbed moisture, particularly at night when humidity peaks in the desert. During the day, the captured water evaporated from the hydrogel, condensing on the glass.

Throughout the test, the device functioned efficiently in various humidity levels, producing between 57 to 161.5 milliliters of drinking water daily. Even at its driest, the device outperformed both passive and some powered alternatives.

“This is just a prototype, and there’s plenty of room for improvement,” Liu notes. “For example, we could design a multi-panel system, and we’re working on next-gen materials to enhance efficiency.”

“We envision deploying arrays of these panels in resource-limited areas. Their vertical design means they occupy minimal space, allowing multiple panels to continuously collect water for household use,” adds Zhao, who plans further trials in various regions globally.