Customized Two-Dimensional Nanostructured MoO₃ Inks For Spectrally Selective UV Chromic Patches

Ultraviolet (UV) radiation exposure plays an important role in human health. However, excessive exposure can lead to skin injuries and melanoma. It is crucial to have a technology that can monitor exposure, particularly to UV A, which penetrates the human skin the most and also assists in building healthy sun habits in the general population. Current sensors do not offer the needed combination of narrow optical absorbance, ease of use, and low cost. Here, we report MoO3 photochromic inks that are customized to the skin complexion based on Fitzpatrick’s skin typing system. The ink is subsequently incorporated into bioelastomers to make “stick-on” UV patches that provide a qualitative assessment of UV A exposure to a user on the go. The photochromism of the patch upon UV exposure is correlated to the calculated percentages of the minimal erythema dose (MED) limits. The patch gives a visual indication of the levels of UV A exposure, which will allow the users to make informed choices to avoid overexposure and prevent skin damage. The patch is fabricated using a manufacturing-compatible screen printing process. This technology has the potential to drive behavioral changes in the population and move toward an aware and sun-smart community.