Magic Ink
The world's first rewritable tattoo ink, taken through clinical studies and onto the market.
Point a flashlight at your arm and a tattoo appears. Point a different one at it and the tattoo goes away. The ink stays in the skin the whole time, doing what tattoo ink has always done, except that the image it holds is now yours to change.
The pigment is photochromic: a molecule that changes shape, and therefore color, when it absorbs light. We seal it inside a shell of medical-grade polymer, the same material already trusted inside the body in dermatology, dentistry and bone surgery. The shell keeps the particles where the artist put them and keeps the chemistry doing only what it should. Ultraviolet light switches the design on, visible light switches it off, and it happens fast enough to watch. In the dish it survives more than ten thousand cycles without fading.
So the tattoo becomes editable. Draw it, wear it, erase it, draw something else in the same skin next year, with a light pen rather than a laser and a dermatologist. What is permanent is the canvas, not the picture.
With tattoo artist Keith “Bang Bang” McCurdy we took it out of the laboratory: through first-in-human clinical studies, where it healed and performed comparably to conventional inks across a range of skin types with no adverse effects, and onto the market in May 2025. The activation device is patented and the clinical data are published.
The same chemistry has a quieter application we care about just as much. Radiotherapy patients receive small permanent tattoos to align the beam, and those marks outlast the illness by decades as a daily reminder of it. A mark that can be switched on for treatment and switched off afterward does the clinical job and then gets out of the way.
Carson J. Bruns, Associate Professor, ATLAS Institute and the Paul M. Rady Department of Mechanical Engineering, University of Colorado Boulder.