Innovative sunscreen prototype offers UV protection and cooling
According to the journal "Nano Letters," a prototype sunscreen with SPF 50 has been developed. This sunscreen not only shields the skin from UV radiation but also provides cooling through a process known as radiative cooling.
Typical sunscreens protect the skin from the harmful effects of UV radiation but don't offer a cooling effect. However, this new cream offers protection against both UV radiation and solar heat by utilizing radiative cooling.
Radiative cooling involves reflecting or emitting heat from an object, leading to its cooling. This effect is already used in creating fabrics and coatings that can cool or heat environments, such as 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 correct size to create a cooling effect.
Prof. Rufan Zhang and his colleagues from Tsinghua University in Beijing decided to adjust the size of TiO2 nanoparticles to develop a sunscreen that provides both UV protection and cooling.
The team formulated 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 created a material that reflects both UV radiation and solar heat. The UVB protection factor (SPF) was approximately 50, and the sunscreen showed water resistance and maintained its effectiveness after 12 hours of simulated sun exposure (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 (in a hot and humid environment) about 6°C cooler than uncoated skin and about 3°C cooler than when protected by commonly available sunscreens.
This promising protective agent is cost-effective, at only $0.92 (CAD 1.24) for 10 grams of the mixture, which is comparable in price to sunscreens already on the market.
