Reversible and Photochromic Peony-Shaped Hairpin Prepared from Electrospun Hybrid Nanofibers for Visualized Solar UV Radiation Detector

Because of the detrimental effects of excessive exposure to solar ultraviolet radiation (UVR) on human skin health, wearable UVR detectors have attracted more and more attention. Inspired by the artwork "Tian-tsui hair pin with flora decoration" from the Palace Museum, a reversible and photochromic peony-shaped hairpin is designed to realize the visualized detection of solar UV radiation. It is prepared via electrospinning a mixed solution containing thermoplastic polyurethanes (TPUs) and Zn-MOF@WO3 onto microfiber nonwoven fabrics (MFNFs). Because of the enhanced UV responsive and photochromic capability from Zn-MOF@WO3 as well the excellent flexibility from TPUs and MFNFs, the obtained hairpin presents an excellent photoresponsive and wearable performance. When exposed to UV radiation from sunshine, the hairpin switches from white to light blue and finally to blue with radiation time. The colors light blue and blue can be used to indicate the UV radiation doses for the synthesis of vitamin D and the induction of erythema, respectively. With the assistance of oxygen in air, the hairpin recovers to its original state after being maintained in a dark atmosphere for 12 h. Even after six cycles of exposure to UV radiation and recovery in the dark, the photochromic performance almost remains unchanged. Only a minor reduction of 5% is observed. As a traditional wearable headdress in China, the peony-shaped hairpin prepared from the hybrid nanofibers not only presents oriental elegance but also is suitable for cyclical use in the daytime to monitor UV radiation for skin health management.