Hybrid Hydrogel-Based Skin Health Monitor for Tracing Solar UV Radiation in Aqueous Environments

Inspired by the Chinese wood oil coating on umbrella,an ionicpolymer layer is coated onto hybrid hydrogels to realize monitoringof the solar ultraviolet (UV) radiation dose in aqueous environments.The hybrid hydrogels are synthesized by introducing the photocatalystgraphitic-carbon nitride (g-C3N4) nanosheetsinto the radically polymerized hydrogels from the monomer di(ethyleneglycol) methyl ether methacrylate (MA) and oligo(ethylene glycol)methyl ether methacrylate (MA(300)). Thus, g-C3N4 are physically embedded in the hydrogels. Owing tothe existence of inorganic nanoparticles (g-C3N4 nanosheets) and hydrogels, the obtained hydrogels containing g-C3N4 nanosheets are named as hybrid hydrogels. Becauseg-C3N4 can decompose the dye methylene blue(MB) by photodegradation and the decomposition capability is correlatedto the absorbed UV radiation dose from the sunshine, the solar UVradiation dose can be easily traced by the discoloration extent ofdyed hybrid hydrogels. To avoid the possible dye leakage during aquaticsports activities, such as swimming in a lake or surfing in the seaside,the acetamide/zinc perchlorate hexahydrate (AC/ZPH)-based ionic polymeris coated onto the hybrid hydrogels. Owing to the combined effectsof the dense structure as well as the existence of positive and negativeions in the AC/ZPH layer, the coated hybrid hydrogels present excellentresistance against dye leakage. To overcome the frangibility of thehydrogels, microfiber nonwoven fabrics (MFNF) are used as a substratefor the sensor. The obtained hybrid hydrogel-based UV radiation monitorpresents excellent dye leakage resistance as well as flexibility andstrength. Thus, it is very suitable for wearable devices to monitorskin health in the aqueous environment under sunshine.