Would you like sunscreens to make you feel cooler?

 If yes, this novel product would be your choice. Honestly, I hate using sunscreens because they not only do not make me cool but also make me feel hot and sweaty. Sunscreens are creams or lotions that help block the sun rays from damaging the skin provided they are applied enough and repeatedly during long sun exposure. As sunscreens block our sweat glands, some people feel hot after utilizing them. This might prevent us from consuming sunscreens which exposes us to dangerous skin damage.

Researchers succeeded in making a new sun protection product that might resolve this issue [1]. This sunscreen radiates the sun’s rays, reducing the amount of energy that is received by the skin; this is why you can feel cooler compared to your surroundings after applying it. It uses the advantage of Radiative Cooling which is a zero-energy-consumption technology and is already used in radiative cooling fabrics. The researchers who introduced this product claim it cools human skin by 2.3-6.1 ^oC more than other sunscreens and performs 4.2-6.0 ^oC better than bare skin.

TiO₂ is an important ingredient of most of the sunscreens with an adjustable reflectivity. The scattering effect increases when the wavelength of the irradiating wave and the diameter of the spherical nanoparticles are comparable (Mie scattering theory). Therefore, by changing the particle size of TiO₂ nanoparticles the reflection of heat from its surface can be tuned. In this work [1], it was seen that particles with a diameter larger than 0.2 micrometres had strong reflectivity in the solar waveband. The solar band includes a range of wavelengths, therefore, a range of particle sizes were mixed in this sunscreen to cover all the received irradiation.

Ideally speaking, this should be a ground-breaking product for the climate change era. But on the other hand, sunscreens block the pores of sweat glands which makes us feel hot. So, which one of these two contradictory effects is the winner? What is the outcome? Will this product really make you feel cooler? Human trials with applying this sunscreen in normal activities should be the next step in this research so that we can confidently comment on its cooling efficiency.

 

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Written by Soheil Aber

https://www.linkedin.com/in/soheilaber/

https://x.com/SoheilAber

#KnowledgeInANutshell

#sunscreen

#sunprotection

#beach

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Bibliography

1.         Xu, J., Wu, X., Li, Y., Zhao, S., Lan, F., Xi, A., Huang, Y., Ding, Y., Zhang, R.: High-Performance Radiative Cooling Sunscreen. Nano Lett. 24, 15178–15185 (2024). https://doi.org/10.1021/acs.nanolett.4c04969