Arm tattoo before and after light activation.
Image credit: Matter & Light, Bruns et al., CC BY-SA
Researchers at the University of Colorado Boulder have created tattoo ink that switches on under an ultraviolet (UV) flashlight and off under bright white light.
The ink, called PhotoTat takes aim at the biggest drawback of body art. A tattoo is permanent, and removal is painful, expensive, and often incomplete. About a quarter of people with tattoos report dissatisfaction with them. On the positive side, more than a third of US adults without a tattoo say they have considered getting inked, but the authors suggest irreversibility may be keeping them from pulling the trigger.
Lead researcher Carson Bruns compares PhotoTat ink to a switch. UV light turns it on, and you can turn it off again “when you go to grandma’s house.”
The ink comes in blue, magenta, and yellow and can be mixed into a range of colors. Each color is a dye sealed inside microscopic beads of PMMA, a plexiglass-like plastic also used in dermal fillers. The dyes are nearly invisible at rest. A two to three second blast from a UV LED turns them vivid, and a bright white LED held against the skin erases them in seconds. Under ordinary indoor lighting, the color lasts hours to days depending on how bright the room is.
Bruns, who has tattoos of his own, had PhotoTat inks implanted in his leg between January 2024 and January 2025. The paper reports the inks healed normally and still switched on and off over two years later. However, the authors say a single-subject pilot cannot support general claims about safety or performance across skin types.
The medical use for this new ink may be more beneficial than the cosmetic one. Radiation therapy patients often receive small permanent tattoos that guide the beam, and Bruns says those marks can become a lasting reminder of a traumatic experience. In theory, PhotoTat could be switched on in the clinic and then switched off before the patient goes home.
While the applications are promising, the ink is not without its flaws. The blue dye wears out quickly – within as few as 10 on-off cycles, it leaves a permanent purple residue that stays visible even when the ink is switched off. Magenta and yellow held up better. The inks also lack a true cyan and a white, so the palette is narrow and the pigments cannot lighten skin.
Anyone hoping to hide a PhotoTat outdoors would also need sunscreen. Ambient UV, even on overcast days, pushes the ink toward its on state. In the skin models, SPF 30 sunscreen applied over an activated PhotoTat turned it off within minutes in sunlight.
If you're looking to get tatted up with the new ink, you're going to have to wait. No version of PhotoTat has been cleared for use in humans. Cytotoxicity, sterility, and purity testing still has to be completed, with larger clinical studies underway.
