A team of Australian researchers has created a safe paper sensor capable of measuring sun exposure while taking into account the wearer’s skin tone and sunscreen use. The investigators used an inkjet printer to layer titanium dioxide and a food dye onto strips of paper. Titanium dioxide is safe and already used in sunscreen lotions, and when light hits it, it makes the dye next to it change color proportionally to the exposure. Sticking a flexible neutral density filter onto the paper that reflects one’s skin tone and the kind of sunscreen used, allows the device to provide personalized results.
From the study abstract in journal ACS Sensors:
The sun exposure sensor works by employing titanium dioxide (TiO2) as a photocatalyst to degrade the food dyes resulting in gradual discoloration of this film. The PVP serves as a binder to allow film formation. The discoloration can be observed by the naked eye or quantitatively monitored using UV–vis reflectance spectra. Finally, discoloration of the films was calibrated to match UV exposure time of different skin types, by using different UV neutral density filters with the ability to transmit between 1.5% and 70% of the irradiant UV light from the sources to the photoactive film.
Study in ACS Sensors: Paper-Based Sensor for Monitoring Sun Exposure
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