Scientists from University of Sydney and start-up Dewpoint Innovations have created a porous polymer coating that reflects up to 97% of sunlight and radiates heat into the air, keeping surfaces up to 6 degrees cooler than the surrounding air even under direct Sun. This process creates ideal conditions for atmospheric water vapor to condense into droplets on the cooler surface, the way steam condenses on your bathroom mirror.
Experimental set-up on the roof of the Sydney Nanoscience Hub. Image credit: University of Sydney.
“This technology not only advances the science of cool roof coatings but also opens the door to sustainable, low-cost and decentralized sources of fresh water — a critical need in the face of climate change and growing water scarcity,” said University of Sydney’s Professor Chiara Neto.
In the six-month long outdoor study conducted on the roof of the Sydney Nanoscience Hub, dew could be collected over 32 % of the year and so could provide a sustainable and predictable supply of water even in periods with no rain.
Under optimum conditions, the coatings can harvest up to 390 mL of water per square meter each day — enough for a 12-sq.m. surface to supply the daily drinking needs of one person.
The study, shows that passive cooling and atmospheric water capture can be integrated into a paint-like material for large-scale use.
Larger collection areas mean the paint could be versatile in industry: water for animals, for horticulture of high-value plants, for use in cooling by misting, or for use in hydrogen production.
Unlike traditional white paints, the porous coatings, made of polyvinylidene fluoride-co-hexafluoropropene (PVDF-HFP) do not rely on ultraviolet-reflective pigments such as 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, 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.”
Over the six-month outdoor trial, the researchers recorded cooling and water collection data minute-by-minute, confirming robust performance with no degradation under harsh Australian Sun. Similar technologies have been shown to quickly deteriorate.
Beyond water harvesting, these coatings could help reduce urban heat island effects, lower energy needs for air-conditioning and provide climate-resilient water sources in regions facing growing heat and water stress.
“The research also challenges the assumption that dew collection only works in humid climates,” Professor Neto said.
“While humid conditions are ideal, dew can form even in arid and semi-arid regions where night-time humidity rises.”
“It’s not about replacing rainfall but supplementing it — providing water where and when other sources become limited.”
The team’s work was published October 30 in the journal Advanced Functional Materials.
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Ming Chiu et al. Passively Cooled Paint-Like Coatings for Atmospheric Water Capture. Advanced Functional Materials, published online October 30, 2025; doi: 10.1002/adfm.202519108
