Now you see them, now you don’t: the new photosensitive tattoos
PhotoTat ink is only visible under UV light
You may be able to turn your tattoos on and off in the near future. A new type of tattoo ink uses light to make the body markings appear and disappear. The result is customizable body art.
Light switch
Scientists engineered PhotoTat, tattoo ink that is “permanent yet rewritable,” said a study published in the journal Matter & Light. The material is “nearly invisible at rest, colored within seconds under ultraviolet light and erased by white light.” It is “made from dyes and a plexiglass-like material common in many medical technologies on the market today, including dermal fillers,” said a release about the study.
To develop the UV-activated ink, researchers used three photochromes, “molecules that can change color in response to different wavelengths of light,” in blue, magenta and yellow, said The Scientist. These molecules were then encapsulated in poly(methyl methacrylate) (PMMA) nanoparticles, which are known for their “safety record and biocompatibility.” The three colors are mixed in different combinations and ratios, producing 16 different shades.
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Human chameleon
PhotoTat can be “combined with conventional tattoo ink,” said Live Science (a sister site of The Week). For example, a permanent black ink design “could contain hidden PhotoTat elements that appear only when activated.” The ink is ideal for “people who love tattoos and have lots of tattoos but just want something kind of fun and playful,” Carson Bruns, a study co-author, said to the outlet.
PhotoTat can have additional practical applications, including for medical tattoos like those done on cancer patients undergoing radiation therapy. “With PhotoTat,” Bruns said in the release, “we could turn an involuntary medical tattoo into something that’s only visible to the doctor when you go in the clinic.”
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Devika Rao has worked as a staff writer at The Week since 2022, covering science, the environment, climate and business. She previously worked as a policy associate for a nonprofit organization advocating for environmental action from a business perspective.

