Sunscreen revolution: New formula cools while protecting
According to the journal "Nano Letters," a prototype sunscreen with SPF 50 has been developed, which not only protects the skin from UV radiation but also provides a cooling effect through radiative cooling.
Using typical sunscreen protects the skin from the harmful effects of UV radiation but does not provide cooling. However, the new cream offers protection against both UV radiation and solar heat by utilising radiative cooling.
Radiative cooling involves reflecting or emitting heat from an object, leading to its cooling. This effect is already utilised in the creation of fabrics and coatings that can both cool and heat, such as those used in 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 appropriate size to induce a cooling effect.
Prof. Rufan Zhang and his colleagues from Tsinghua University in Beijing decided to adjust 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, moisturising cream, pigments, and a commonly used cosmetic silicone polymer called polydimethylsiloxane.
By appropriately selecting the sizes of the TiO2 nanoparticles, they managed to create a material that reflects both UV radiation and solar heat. The UVB protection factor (SPF) was around 50, and the sunscreen demonstrated water resistance and maintained its effectiveness after 12 hours of simulated sun exposure (xenon lamp).
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 degrees Celsius cooler than uncoated skin and about 3 degrees Celsius cooler than when protected by commonly available sunscreens.
The potential protective agent is inexpensive - it costs only $0.92 (£0.73) for 10 grams of the mixture, which is comparable in price to sunscreens already available on the market.
