Multicolored tattoo ink activated by light

Researchers have created multicolored tattoo inks that change color when exposed to specific wavelengths of light. These inks, called PhotoTat, allow tattoo designs to be hidden or revealed based on the lighting conditions.

Tattoo visibility controlled by light exposure

The PhotoTat technology uses photochromic dyes inside nanoparticles that alter their color depending on the light they are exposed to. A 365-nanometer ultraviolet LED can activate the pigments in about two to three seconds, and the colors remain visible for hours or days under normal indoor lighting but fade quickly in sunlight.

Permanent tattoo with optional invisibility

According to Carson Bruns, a professor of biomedical engineering at the University of Colorado in Boulder, the tattoo can stay permanently on the skin, but if someone no longer wants it visible, they can use light to deactivate it. The system uses three primary colors—blue, magenta, and yellow—each activated by a different wavelength of light.

Customizable and safe tattoo option

The PhotoTat system allows for customizable tattoos that can be adjusted to personal preferences. Currently, only the violet version of the ink has been commercialized after passing safety tests. It is sold online for $100 and is available for purchase in euros. Bruns aims to bring other colors to market and lower costs to make the technology more widely available.