Innovative sunscreen blocks UV and keeps skin 11°F cooler
According to the journal "Nano Letters," a prototype sunscreen with SPF 50 has been created that not only protects the skin from UV radiation but also provides cooling through radiative cooling.
Conventional sunscreens protect the skin from the harmful effects of UV radiation but do not offer any cooling. However, this new cream guards against both UV radiation and solar heat by using radiative cooling.
Radiative cooling involves reflecting or emitting heat away from an object, which results in its cooling. This effect is already being used to develop fabrics and coatings that can both cool and heat, such as those used for homes.
Some passive radiative cooling technologies use titanium dioxide (TiO2), a white substance that reflects heat. TiO2 particles are also used in sunscreens to reflect UV light, but they are not the proper size to induce a cooling effect.
Prof. Rufan Zhang and his colleagues from Tsinghua University in Beijing decided to modify the size of TiO2 nanoparticles to create a sunscreen that acts as both UV protection and a coolant.
The team developed their sunscreen by combining six ingredients: TiO2 nanoparticles, water, ethyl alcohol, moisturizing cream, pigments, and a commonly used cosmetic silicone polymer called polydimethylsiloxane.
By carefully selecting the sizes of the TiO2 nanoparticles, they succeeded in creating a material that reflects both UV radiation and solar heat. The UVB protection factor (SPF) was approximately 50, and the sunscreen demonstrated water resistance and maintained its effectiveness after 12 hours of simulated sun exposure using a xenon lamp.
When applied to the skin of animals and humans, the product did not cause irritation. After being coated with the prototype sunscreen, human skin remained about 11 degrees Fahrenheit cooler than uncoated skin and about 5 degrees Fahrenheit cooler than when protected by commonly available sunscreens in a hot and humid environment.
The potential protective agent is cost-effective—it costs only $0.92 for 0.35 ounces of the mixture, which is comparable in price to sunscreens already on the market.
