AI-guided sponge pulls clean water from air using sunlight

Refined wood, salt, sunlight, and artificial intelligence might soon deliver clean drinking water from thin air—even in the driest regions of the world. That’s the promise behind a new invention developed by researchers from Australia and China. Their novel, wood-based material not only absorbs water from the air but also releases it using only sunlight, offering hope for a world facing growing water shortages.

The device, made from refined balsa wood, works like a high-tech sponge. It captures moisture from the air and, when heated by the sun, releases it as clean water into a cup. Even in low humidity and freezing temperatures, it remains functional—offering water in conditions where many other systems fail.

The material at the heart of this technology is a blend of wood, lithium chloride, and a solar-absorbing surface made of carbon nanotubes. These ingredients form a strong, porous sponge that can absorb water vapor from air at humidity levels ranging from 30% to 90%. That’s a wide range, making the device useful in many parts of the world.

Once exposed to sunlight, the sponge heats up. This causes the absorbed water to evaporate from the material and collect in a container, ready for drinking.

Researchers found that in laboratory tests, the material could release nearly all its absorbed water within 10 hours of sun exposure. Even at just 30% humidity, it pulled about 0.6 milliliters of water per gram from the air. And at 90% humidity, it absorbed about 2 milliliters per gram.

Freshwater scarcity is a growing problem worldwide. Nearly 80% of people face serious water shortages. Traditional methods like fog harvesting or radiative cooling often don’t work well in dry areas. That's where atmospheric water harvesting (AWH) comes in. By pulling water directly from the air, AWH systems don’t rely on rivers, lakes, or underground sources.

The use of wood as a base for the sponge isn’t just a clever choice—it’s a strategic one. Wood is naturally porous and full of channels that can hold water. It’s also biodegradable, cheap, and widely available. Researchers chose balsa wood for its sponge-like structure, which helped them build a stable, reusable material.

Lithium chloride, the salt used in the device, is known for its ability to absorb water even in low humidity. But in powdered form, it can clump or leak. By embedding it in wood, researchers avoided these problems and created a stable system for absorbing and storing water.

The researchers didn’t just stop with good materials. They used machine learning to fine-tune the design and predict how the material would perform under different environmental conditions. Random forest and long short-term memory (LSTM) models showed high accuracy in predicting both water absorption and release rates. One of the best models achieved a prediction accuracy with an R² value of 0.988 for absorption rate.

An analysis using the Shapley Additive Explanations method revealed that three main factors influence how well the material works: how long it absorbs moisture, how much salt it contains, and the relative humidity of the air. Surprisingly, temperature played a smaller role.

These models helped researchers visualize how small changes in conditions affected water collection. That means future improvements could be designed more quickly and accurately, reducing trial-and-error in the lab.

One of the most impressive aspects of the sponge device is its durability. In outdoor tests, it collected up to 2.5 milliliters of water per gram overnight, then released most of it during the day, reaching a daily water collection efficiency of 94%. The device held up well through 10 cycles of absorbing and releasing water, with less than 12% performance drop.

Even after being stored at −20 °C for 20 days, the sponge still absorbed water and worked as expected. This freeze resistance makes it especially valuable for emergency use in cold climates.

Dr. Derek Hao from RMIT University in Melbourne led the study with support from Dr. Junfeng Hou at Zhejiang A&F University and five other Chinese research institutes. Hao said the design combines nature-inspired materials with smart engineering. Its simple structure means it could be mass-produced and deployed in remote or disaster-hit areas.

Each sponge cube is small—just 15 cubic millimeters. But by combining multiple cubes or scaling up the system, larger volumes of water could be collected. The device could be placed in arrays and operated entirely on solar power, without needing batteries or electricity.

Researchers are now in talks with industry partners about pilot-scale production. Hao noted that integrating the device with solar panels and smart sensors could allow it to run day and night. Sensors could monitor air temperature, humidity, and solar energy to optimize the system’s operation.

Hao envisions future models that are even smarter. With better design platforms, guided by AI, researchers could test new combinations of materials without long lab experiments. This could speed up innovation and lead to devices that are more efficient, cheaper, and better suited to different climates.

The breakthrough builds on years of research into new materials for AWH. Many groups have tested hydrogels, aerogels, and composite materials to improve water capture. These materials combine salts with flexible matrices like cellulose, guar gum, and even bacterial cellulose. They absorb more water and release it more easily than older materials like silica gel or zeolite.

Some of the latest designs use natural materials like loofah, rapeseed pollen, and sodium alginate to create sponges that are both eco-friendly and effective. These materials can also biodegrade after use, reducing environmental harm.

Still, many of these earlier methods involve costly or complex manufacturing. The new wood-based sponge offers a simpler, cheaper alternative. Its mix of affordability, performance, and smart design could make it one of the most promising technologies for solving the global water crisis.

Research findings are available online in the Journal of Cleaner Production.

Note: The article above provided above by The Brighter Side of News.

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