Cooling Paint That Harvests Water from Thin Air

Researchers from the University of Sydney and start-up Dewpoint Innovations have created a nanoengineered polymer coating that functions like paint, capable of passively cooling buildings and extracting water from the air, all without using any energy.

The innovation could help address global water shortages while cooling buildings and reducing reliance on energy-intensive cooling systems.

Led by Professor Chiara Neto, the research team developed a porous polymer coating that reflects up to 97% of sunlight and releases heat into the atmosphere, keeping surfaces up to six degrees cooler than the surrounding air, even in direct sunlight. This cooling effect allows atmospheric water vapour to condense into droplets on the surface, much like the steam that forms on a bathroom mirror.

Professor Neto from the University of Sydney Nano Institute and School of Chemistry stated that the findings could have wide-ranging implications.

“This technology not only advances the science of cool roof coatings but also opens the door to sustainable, low-cost and decentralised sources of fresh water – a critical need in the face of climate change and growing water scarcity,” she said.

In a six-month outdoor study conducted on the roof of the Sydney Nanoscience Hub, dew was collected for 32% of the year, demonstrating the potential for a sustainable and consistent water source even during rain-free periods. The coating can collect up to 390 mL of water per square metre per day in the best conditions. This is enough for a 12-square-metre surface to meet one person's daily drinking water needs.

Published in Advanced Functional Materials, the study demonstrates that passive cooling and atmospheric water harvesting can be combined into a paint-like material suitable for large-scale applications.

With larger collection areas, the coating could have wide industrial applications—provide water for livestock, irrigate high-value crops, support cooling systems through misting, or supply water for hydrogen production, which requires about nine litres of water per kilogram of hydrogen during electrolysis.

Cooling Cities, One Drop at a Time

Unlike conventional white paints, the porous coatings composed of polyvinylidene fluoride-co-hexafluoropropene (PVDF-HFP) achieve their cooling effect without using ultraviolet-reflective pigments like titanium dioxide.

“Our design achieves high reflectivity through its internal porous structure, delivering durability without the environmental drawbacks of pigment-based coatings,” said Dr Ming Chiu, the study’s lead author and chief technology officer of Dewpoint Innovations.

“By removing UV-absorbing materials, we overcome the traditional limit in solar reflectivity while avoiding glare through diffuse reflection. This balance between performance and visual comfort makes it easier to integrate and is more appealing for real-world applications.”

During the six-month outdoor trial, the research team continuously monitored both cooling and water collection data, confirming that the coating maintained strong performance without any degradation under the intense Australian sun – a significant improvement over similar technologies that tend to degrade quickly.

In addition to water harvesting, the coatings could help mitigate urban heat island effects, reduce air-conditioning energy demands, and provide climate-resilient water sources in regions increasingly affected by heat and water stress.

From Research to Real-World Impact

To transition the discovery from laboratory research to real-world application, Dewpoint Innovations is developing a water-based paint formulation that can be easily applied using standard rollers or sprayers.

“At Dewpoint, we’re proud to partner with the University of Sydney to bring this breakthrough in passive atmospheric water harvesting to life through advanced paint-based coatings,” said Perzaan Mehta, CEO of Dewpoint Innovations.

In 2022, the University of Sydney licensed the Neto Group's innovation to the start-up Dewpoint Innovations. Its commercialisation represents a significant advancement towards scalable and sustainable solutions for water harvesting and passive cooling, with promising applications in the built environment, agriculture, remote communities, and urban infrastructure.

Source: University of Sydney