# Engineers Develop Photochromic Tattoo Ink That Responds to Light University of Colorado researchers create light-sensitive ink that changes transparency upon UV exposure. - **Source:** [Popular Science](https://www.popsci.com) - **Published:** 2026-10-19 - **Topic:** [Business](https://brifing.si/c/business) - **Original article:** - **On Brifing:** https://brifing.si/s/f5c0df2d-2515-4b78-9b07-29e734500b66 ## Innovative Light-Sensitive Ink Engineers at the University of Colorado Boulder have developed a novel tattoo ink that physically alters its appearance based on light exposure. Unlike permanent traditional tattoos, this dye reacts to visible or ultraviolet light. The research team recently detailed their findings in the journal Matter Light, showcasing potential applications beyond simple aesthetics. ## Mechanism of Transparency The ink relies on tiny spheres of acrylic glass containing photochromes, similar to the technology used in transition lenses. When exposed to UV rays, these spheres flatten into transparency. Upon absorbing visible light photons, the chemical bonds break, allowing the spheres to return to their original shape, effectively hiding or revealing the design. ## Practical Testing and Application Carson Bruns, a nanoscientist and co-author of the study, tested the ink on his own leg over a twelve-month period. He utilized various dye combinations, including yellow, blue, and magenta. The ink demonstrated consistent responsiveness to light stimuli and maintained its functional integrity for over two years during the testing phase. ## Previous Commercial Success Bruns is not new to this field, having previously developed a commercial product called Magic Ink. That earlier iteration turns magenta when exposed to UV light, which he used to create solar freckles to track sun exposure. This new disappearing ink represents a significant technical evolution from his previous work in nanosciences. ## Beyond Aesthetic Body Art The research team aims to move past parlor tricks and explore clinical utility for this technology. Future iterations could serve as temporary markings for medical procedures, specifically to maintain high accuracy during direct radiotherapy sessions. This would provide a non-permanent, precise way to guide medical equipment on a patient's skin. ## Current Safety and Limitations While the ink has shown success in laboratory settings and on human skin, it remains restricted to research use for now. The team must complete further safety assessments before any commercial or medical rollout can occur. These evaluations are essential to ensure the long-term biological compatibility of the acrylic glass spheres. ## Comparative Material Science The ink functions on principles shared with advanced textiles and optical lenses. By engineering chemical compounds to absorb specific light wavelength photons, the team achieved a reversible state change. This approach highlights a shift in tattoo technology from static pigments toward dynamic, responsive materials that interact actively with the surrounding environment. ## Future Research Trajectory The successful demonstration on pig skin and silicone, followed by Bruns' self-testing, provides a foundation for future development. As the team refines the chemical stability of the photochromic dyes, the focus will shift toward regulatory approval. This technology could eventually redefine how we approach both temporary body art and medical skin marking. ## Sources covering this story - https://www.popsci.com/science/disappearing-tattoo-ink/ — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._