# Engineers Develop Photochromic Tattoo Ink That Responds to Light University of Colorado Boulder researchers create light-sensitive ink for temporary, reversible skin markings. - **Source:** [Popular Science](https://brifing.si/source/cc3d313a-759c-4802-b881-fc8585f35ef9) - **Published:** 2026-10-19 - **Topic:** [Business](https://brifing.si/c/business) - **Original article:** - **On Brifing:** https://brifing.si/s/70a878a1-099a-431e-9767-9b28d9cb53ce ## Innovative Light-Sensitive Ink Technology Researchers at the University of Colorado Boulder have engineered a new type of tattoo ink that physically alters its appearance based on light exposure. Unlike permanent tattoos, this dye shifts between colored and transparent states when exposed to specific visible or ultraviolet light wavelengths, offering a unique approach to temporary body art. ## Mechanism of Photochromic Dye Spheres The ink relies on tiny acrylic glass spheres containing photochromes designed to absorb specific light photons. When exposed to UV rays, these spheres flatten into a transparent state. Upon absorbing visible light, the chemical bonds are altered, allowing the spheres to return to their original shape and color, effectively resetting the tattoo's visibility. ## Practical Testing by Carson Bruns Nanoscientist Carson Bruns, a co-author of the study, has personally tested the ink by tattooing his own leg. Over a twelve-month period, he utilized various dye combinations to verify the ink's responsiveness. The results confirmed that the material remains effective for over two years, maintaining its intended reaction to light exposure throughout testing. ## Evolution from Previous Commercial Products This project builds upon Bruns' previous work, including the commercialized 'Magic Ink' product that shifts to magenta under UV light. Bruns previously used this technology to create 'solar freckles' on his skin as a method for tracking sunlight exposure, demonstrating a long-term interest in developing functional, light-responsive materials for human skin applications. ## Expanding Beyond Cosmetic Applications While currently viewed as a novel development, the research team aims to transition the ink into medical environments. Future iterations could serve as temporary markings for patients undergoing radiotherapy. These precise, light-responsive indicators would help clinicians maintain accuracy during direct radiation sessions, potentially improving patient outcomes through better procedural guidance and monitoring. ## Current Limitations and Safety Protocols The photochromic tattoo dyes are currently restricted to laboratory use and personal testing by the developers. Before the technology can reach a wider market or clinical setting, it must undergo rigorous safety assessments. These evaluations are essential to ensure the long-term biocompatibility of the acrylic glass spheres and chemical compounds within human skin. ## Material Science and Textile Parallels The underlying principles of this ink technology mirror those found in transition lenses and certain advanced textiles. By leveraging photochromic compounds that respond to photon absorption, the team has successfully adapted established industrial material science for dermatological use. This cross-disciplinary approach highlights the potential for smart materials to function directly on biological surfaces. ## Future Outlook for Reversible Tattoos The successful demonstration of this ink on silicone, pig skin, and human subjects marks a significant step in tattoo technology. As the team continues their research, the focus will shift toward optimizing the ink's durability and safety profile. This innovation could eventually redefine how we perceive permanent body modifications and medical marking procedures. ## 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._