Light-Sensitive Ink Offers New Shades of Tattooing

Researchers at the University of Colorado Boulder (CU) have developed “PhotoTat,” a light-activated tattoo ink that can transition between colorful and virtually invisible states on demand.

The technology utilises polymethyl methacrylate nanoparticles – a biocompatible material widely used in medical settings – to encapsulate light-sensitive photochromic dyes. Under standard visible light, the ink remains transparent. However, exposure to ultraviolet (UV) light for two to three seconds activates the pigments, producing vibrant blue, magenta or yellow primary colors. By blending these primary shades, researchers created a full-color palette capable of displaying intricate, temporary designs on skin models and silicone.

While PhotoTat offers exciting possibilities for flexible body art, it also holds major medical potential. Cancer patients receiving radiation therapy often require small, permanent target tattoos, which can serve as persistent reminders of trauma. PhotoTat could replace these with marks that remain invisible until illuminated by UV light during medical appointments. Similarly, the ink could be applied to mark biopsy sites without leaving permanent scars.

In preliminary self-testing, CU team leader Carson Bruns applied the ink to his own skin, confirming it remained functional and light-responsive after two years without adverse effects.

While the ink must still undergo rigorous sterility, purity and toxicity testing before commercial availability, PhotoTat represents a major step toward temporary, re-writeable intradermal art and functional medical markings.

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