New hydrogel material can extract unlimited amounts of water from the air

Researchers at the Massachusetts Institute of Technology (MIT) have developed a superabsorbent hydrogel material. It is capable of absorbing moisture and extracting water from the air.

This groundbreaking material could be a game-changer, particularly in desert and drought-prone regions.

The material is able to swell as it absorbs water vapor. This allows it to continuously draw in moisture even under dry conditions of 30 percent relative humidity.

Remarkably, it does this without any leakage. After absorbing the water, one can heat, condense, and collect it as ultrapure water.

Supercharged hydrogel is the secret sauce

What’s the secret behind this new material’s extraordinary absorbency? The material is a hydrogel, a naturally absorbent substance used in products such as disposable diapers.

The team of engineers supercharged the hydrogel’s moisture-absorbing capabilities by infusing it with lithium chloride. Scientists know this salt for its desiccating power.

Earlier studies limited how much salt could be infused into the hydrogel. This MIT team, however, was able to exceed that limit. They achieved unprecedented levels of moisture absorption even in extremely dry environments.

Carlos Díaz-Marin is a mechanical engineering graduate student at MIT and member of the Device Research Lab.

He said, “We’ve been application-agnostic, in the sense that we mostly focus on the fundamental properties of the material. But now we are 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.”

You can quickly produce hydrogel in massive amounts

If we can manufacture this superabsorbent hydrogel quickly and on a large scale, it could serve as a passive water harvester. Additionally, we could also integrate it into air conditioning units to save energy by dehumidifying the air.

The MIT team sought to improve hydrogels’ moisture-absorbing abilities, particularly from the air. They found that salts like lithium chloride were efficient at absorbing moisture and decided to combine the two.

Gustav Graeber was a member of the MIT team and is now a principal investigator at Humboldt University in Berlin. He said, “The hydrogel can store a lot of water, and the salt can capture a lot of vapor. So it’s intuitive that you’d want to combine the two.”

How the hydrogel was created

In a new approach, the MIT team spent days and even weeks allowing the lithium chloride to infuse into the hydrogel, instead of the usual 24 to 48 hours used in previous experiments.

The results were astonishing. After 30 days, the hydrogels had absorbed up to 24 grams of salt per gram of polymer, quadrupling the previous record.

This record-breaking absorption ability held across a range of humidity levels. In dry conditions of 30 percent relative humidity, the hydrogel captured an astonishing 1.79 grams of water per gram of material.

Díaz-Marin further commented, “Any desert during the night would have that low relative humidity, so conceivably, this material could generate water in the desert.” The focus now, he said, is on improving the rate of water uptake, to allow for faster cycling and more frequent water harvesting.

The team published their study in the journal Advanced Materials. The research was supported, in part, by the U.S. Office of Energy Efficiency and Renewable Energy and the Swiss National Science Foundation.

The innovation showcased by these researchers offers a glimpse of a future where even the driest of regions may have access to a consistent water source.

Material used in diapers was the spark for creating the hydrogel

This astonishingly absorbent hydrogel is a product of MIT’s Device Research Lab. This lab is dedicated to creating innovative materials aimed at solving global energy and water challenges.

The team chose to focus on enhancing the capabilities of hydrogel, a material that people have used for years to absorb moisture, especially in products like diapers.

The team pondered, “Our question was, how can we make this work just as well to absorb vapor from the air?” Díaz-Marin shared. They researched extensively and found that some salts, like rock salt, could efficiently soak up moisture.

 Of these, lithium chloride stood out due to its incredible ability to absorb over ten times its own mass in moisture. However, lithium chloride by itself can only pool the moisture around it without retaining it.

Getting from diapers to a groundbreaking hydrogel material

This led the researchers to combine hydrogel and lithium chloride, resulting in a superabsorbent material that could attract and hold in moisture.

Graeber clarified this approach by stating, “It’s the best of both worlds. The hydrogel can store a lot of water, and the salt can capture a lot of water vapor. So it’s intuitive that you’d want to combine the two.”

The innovation of the MIT team, however, didn’t stop there. They noticed that other teams had hit a roadblock when it came to the amount of salt they could infuse into the hydrogel.

Previous attempts were only able to infuse 4 to 6 grams of salt per gram of polymer, yielding absorption of about 1.5 grams of vapor per gram of material in 30 percent relative humidity conditions.

Instead of stopping there, the MIT team decided to push the boundaries. They experimented with a longer infusion process that went on for weeks instead of hours.

The research team sliced tubes of hydrogel into thin disks and placed each disk into a different concentration of lithium chloride solution. They weighed the disks each day to measure how much salt they had absorbed, then returned them to their solutions.

Final results of their work exceeded expectations

The results were striking. After a month-long process, hydrogel incorporated up to 24 grams of salt per gram of polymer. When tested under various humidity conditions, the enhanced gels swelled and absorbed more moisture without leaking.

This happened even at a very low 30 percent relative humidity. At this dry condition, the gels captured a “record-breaking” 1.79 grams of water per gram of material.

Díaz-Marin enthused, “Any desert during the night would have that low relative humidity, so conceivably, this material could generate water in the desert.”

He indicated that their next objective is to enhance the rate at which the material absorbs moisture.

Graeber added, “The big, unexpected surprise was that, with such a simple approach, we were able to get the highest vapor uptake reported to date. Now, the main focus will be kinetics and how quickly we can get the material to uptake water. That will allow you to cycle this material very quickly, so that instead of recovering water once a day, you could harvest water maybe 24 times a day.”

More work ahead to unleash the vast potential of the hydrogel

The research carried out at MIT’s Device Research Lab underlines the vast potential of this superabsorbent material. This could mark a significant advancement in the quest for more sustainable water harvesting and energy-saving practices.

The world awaits the next developments with eager anticipation as we move closer to a future where the scarcity of water in desert regions could be a thing of the past.

More about global water security

Global water security is a critical issue that’s becoming more important due to growing populations, climate change, and increased industrial demand. It refers to the reliable access and availability of clean, safe water for everyone, everywhere. It’s an essential aspect of global security, health, and development.

There are numerous challenges that threaten global water security. Here are some of them:

Water Scarcity

Water scarcity is caused by a combination of factors like overuse, wastage, pollution, and climate change. The United Nations estimates that by 2025, nearly two-thirds of the world’s population could be under “water-stressed” conditions.

Climate Change

Changes in weather patterns due to climate change can lead to droughts, floods, and unpredictable rainfall, making water availability less predictable.

Population Growth and Urbanization

Rapid population growth and urbanization often lead to increased demand for water, sometimes outpacing the supply.

Pollution

Pollution from industry, agriculture, and domestic waste can contaminate water sources, making them unsafe for human consumption and reducing the overall available clean water.

Inadequate Infrastructure

In many parts of the world, water infrastructure is outdated or inadequate. This can lead to significant water loss due to leakage or inefficient distribution systems.

Political and Transboundary Issues

Water sources often cross national borders, and disagreements over usage rights can lead to conflicts. Effective water management and cooperation between countries are essential for global water security.

Addressing these challenges requires a combined global effort. Potential solutions include improved water management strategies, increased investment in infrastructure, implementing water conservation measures, pollution control, and using new technologies like the superabsorbent hydrogel developed by MIT engineers.

Achieving global water security is not just about having enough water, but also about ensuring the water is safe and can be accessed by everyone. It’s an integral part of sustainable development and vital for the health and survival of communities around the world.