Scientists from the University of Sydney and startup Dewpoint Innovations have created a porous polymer coating that reflects up to 97% of sunlight and radiates heat into the air, keeping surfaces 6 degrees cooler than the surrounding air even in direct sunlight. This process creates ideal conditions for atmospheric water vapor to condense into droplets on a cooler surface, similar to how steam condenses on a bathroom mirror.
Experimental setup on the roof of the Sydney Nanoscience Centre. Image credit: University of Sydney.
“This technology not only advances the science of cold roofing, but also opens the door to sustainable, inexpensive and decentralized sources of fresh water – a critical need in the face of climate change and growing water scarcity,” said University of Sydney professor Chiara Neto.
In a six-month outdoor study conducted on the roof of the Sydney Nanoscience Centre, dew can accumulate at more than 32% per year and thus can provide a stable and predictable water supply even during periods without rain.
Under optimal conditions, the coatings can collect up to 390 ml of water per square meter per day – this is enough for a house with an area of 12 sq.m. surface to meet one person's daily drinking needs.
The study shows that passive cooling and atmospheric water capture can be integrated into a paint-like material for large-scale use.
Large collection areas mean that the paint can be used for industrial purposes: for water for animals, for growing valuable plants in horticulture, for spray cooling or for use in hydrogen production.
Unlike traditional white paints, porous coatings made from polyvinylidene fluoride-co-hexafluoropropene (PVDF-HFP) do not contain ultraviolet reflective pigments such as titanium dioxide.
“Our design is highly reflective due to its internal porous structure, providing durability without the environmental disadvantages of pigment-based coatings,” said Dr. Ming Chiu, CTO of Dewpoint Innovations.
“By removing UV-absorbing materials, we overcome the traditional limit of solar energy reflection while avoiding glare through diffuse reflection.”
“This balance between performance and visual comfort makes it easier to integrate and more attractive for real-world applications.”
During six months of outdoor testing, researchers recorded minute-by-minute cooling and water collection data, confirming reliable performance without degradation under the harsh Australian sun. Such technologies have been shown to quickly become unusable.
In addition to water harvesting, these coatings can help reduce the urban heat island effect, reduce energy requirements for air conditioning, and provide climate-resilient water sources in regions experiencing increasing heat and water stress.
“The study also challenges the assumption that dew harvesting only works in humid climates,” Professor Neto said.
“Although humid conditions are ideal, dew can form even in arid and semi-arid regions where humidity increases at night.”
“This is not about replacing rainfall, but supplementing it—providing water where and when other sources become limited.”
teams Job was published on October 30 in the magazine Advanced functional materials.
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Ming Chiu etc.. Passively cooled paint coatings for trapping atmospheric water. Advanced functional materialspublished online October 30, 2025; doi: 10.1002/adfm.202519108
