Overview
- A University of Colorado Boulder team led by Carson Bruns published PhotoTat in the journal Matter & Light on October 9, 2026, reporting inks that change appearance when exposed to specific light.
- PhotoTat uses three light‑sensitive dyes sealed in tiny polymethyl methacrylate (PMMA) particles that are nearly invisible in normal light and turn bright blue, magenta or yellow under 365 nm UV light.
- The researchers wrote patterned images onto silicone and excised pig skin with patterned UV, stencils and projection, and one human participant’s three colour channels remained rewritable for about 1.4 to 2.2 years.
- Key practical limits remain: the formulations still need independent tests for toxicity, sterility and purity, sunlight UV can push the inks toward a partly visible state without UV protection, and visibility falls as skin pigmentation increases.
- The team highlights medical uses such as clinic‑visible radiotherapy or biopsy marks that are hidden most of the time, but PhotoTat is not available to the public and requires further refinement and safety clearance before use.