Butterfield, J. ., Keyser, S. ., Dikshit, K. ., Kwon, H. ., Koster, M. ., & Bruns, C. . (2020). Solar Freckles: Long-Term Photochromic Tattoos for Intradermal Ultraviolet Radiometry. ACS Nano, 14(10), 13619-13628. https://doi.org/10.1021/acsnano.0c05723 (Original work published 2020)