Thousands of years ago, the Nabataeans flourished in the heart of the desert. Today, the mythical city of Petra, carved directly into the rock, stands as a testament to a prosperity built largely on its role as a vital crossroads on the Silk Road. Yet, while trade explains Petra’s wealth, its survival in such an arid climate is down to something else: its inhabitants were master hydraulic engineers. They devised a sophisticated network of cisterns and reservoirs to guarantee a water supply even during the harshest droughts.
While such ancient systems have largely become obsolete with the rise of modern, large-scale water management networks, new passive designs could help us optimise our water resources and build more resilient cities. One such breakthrough is a smart paint developed by the University of Sydney, which is capable of trapping water from the atmosphere while cooling buildings in the process. Here is how it works.
We have previously explored paints capable of cooling buildings or even "eating" pollution. Now, researchers in Australia have added a new string to the bow: water harvesting. By using a nano-polymer coating, the paint captures moisture without requiring any external energy source. These results have already moved beyond the lab and onto the roof of the university’s nanoscience laboratory.
A six-month pilot test conducted on-site has yielded encouraging data. The initial findings indicate that it is possible to collect dew for 32% of the year, providing a constant, reliable, and sustainable supply without any noticeable drop-off in performance. The research, published in the journal Advanced Functional Materials, demonstrates that in optimal conditions, the paint can harvest up to 390 ml of water per square metre daily. This suggests that just a dozen square metres could meet the drinking water requirements of a single person.
To get into the technical nitty-gritty: while other paints rely on compounds like titanium dioxide as a reflective pigment, this new coating uses PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene copolymer). This material is highly porous, making it ideal for atmospheric water generation (AWG).
The team, led by Professor Chiara Neto, claims the coating reflects up to 97% of solar radiation. This lowers the temperature of the adjacent air by as much as six degrees Celsius, even in direct sunlight. This cooling effect creates the perfect conditions for water to condense, which can then be channelled for drinking or irrigation.
The laboratory is already collaborating with a commercial partner to develop a water-based version of the paint that can be applied to roofs and facades using standard rollers or spray guns. However, there is a catch: PVDF-HFP compounds belong to the PFAS family—often dubbed "forever chemicals." Because these substances do not break down in the environment, some countries are already considering a total ban on their use.
Beyond smart paints that cool surfaces or harvest water, one of the most promising applications lies in tackling urban smog. As recently reported, an innovative self-cleaning, purifying paint uses titanium oxide nanoparticles and olive-leaf extracts to eliminate up to 96% of toxic atmospheric particles upon contact with sunlight. Known as photocatalytic paint, these coatings do more than just strip away toxic particles or gases like nitrogen oxide; they also create surfaces with antibacterial and antifungal properties.
If you are interested in cooling technologies, you might also enjoy our feature on the ancient Egyptian pigment capable of reflecting infrared radiation back into space. This approach, alongside the expansion of urban green spaces, is currently being studied as a key strategy to mitigate the "heat island" effect plaguing our major cities.
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David is a journalist specializing in innovation. From his early days as a mobile technology analyst to his latest role as Country Manager at Terraview, an AI-driven startup focused on viticulture, he has always been closely linked to innovation and emerging technologies.
He contributes to El Confidencial and cultural outlets such as Frontera D and El Estado Mental, driven by the belief that the human and the technological can—and should—go hand in hand.