Sunscreen has always been essential for protecting skin from harmful UV radiation, but innovation takes it further—it helps keep people cool under the blazing sun. Researchers, led by Rufan Zhang, have developed a prototype sunscreen that blocks UV light and uses radiative cooling technology to reduce skin temperature. The breakthrough formula, described in ACS Nano Letters, kept human skin up to 11 degrees Fahrenheit cooler than bare skin and even outperformed existing it in heat reduction.
Radiative Cooling: The Science Behind the Chill of Sunscreen
Radiative cooling is when heat is reflected or radiated away from an object, lowering its temperature. While the technology has been used in cooling fabrics and building materials, this is the first time it’s been successfully integrated into it.
The key to this innovation lies in titanium dioxide (TiO2), a common ingredient in mineral it known for its ability to reflect UV light. Traditionally, TiO2 particles are too small to reflect heat effectively. However, Zhang and his team fine-tuned the size of these nanoparticles to create a dual-action of it that protects against UV rays while also reflecting solar heat.
By combining six ingredients—TiO2 nanoparticles, water, ethanol, moisturizing cream, pigments, and a silicone polymer called polydimethylsiloxane—, the researchers created a formulation with both sun protection and cooling properties.
Impressive Results: SPF, Cooling, and Long-Lasting Effects of Sunscreen
The new sunscreen offers an SPF of approximately 50 and has shown remarkable durability, maintaining its efficacy after 12 hours of simulated sunlight exposure using a xenon lamp. It’s water-resistant, safe, and not irritate when applied to animal or human skin during testing.
Field tests in hot, humid outdoor environments revealed the sunscreen’s cooling power. Skin treated with the formula was up to 11 degrees Fahrenheit cooler than bare skin and up to 6 degrees Fahrenheit cooler than skin treated with commercially available sunscreens.
Affordable Innovation with Commercial Promise
Perhaps the most surprising aspect of the formula is its cost-effectiveness. Producing 10 grams of the mixture costs just $0.92, which puts it on par with standard sunscreens currently on the market.
With global temperatures rising, this could revolutionize how people protect themselves from the sun. Its ability to cool skin while providing UV protection makes it appealing for hot climates and outdoor activities.
The National Key Research Program, the National Natural Science Foundation of China, and the Tsinghua-Toyota Joint Research Fund funded the project. While still in the prototype stage, this dual-action sunscreen could soon become a summer essential, helping people stay cool and protected under the sun’s rays.
Reference: Jiaqi Xu, Xueke Wu, Yunrui Li, Siming Zhao, Fan Lan, Aike Xi, Ya Huang, Yilin Ding, Rufan Zhang. High-Performance Radiative Cooling Sunscreen. Nano Letters, 2024; 24 (47): 15178.
