Tattoos have long been considered something permanent: what is once applied to the skin usually stays with a person for life. But a group of researchers from the University of Colorado Boulder has shown that this is not necessarily the case. The ink can literally be “turned off” and “turned on” with light. In a recent publication in the journal Matter & Light, scientists described a technique where photochromic dyes, enclosed in tiny plexiglass spheres, act as the pigment. Under ultraviolet light, such a design appears, and under ordinary visible light, it disappears.
How the Phototat Technology Works
The authors named the method Phototat. It is based on three basic dyes: magenta, yellow, and cyan. By mixing them in different proportions, almost any shade can be obtained, meaning it’s a full-color tattoo, not a monochrome sketch. The pigment itself is packaged in nanoscale beads, which are held in the dermis, ensuring the stability of the design for a long time.
This is a significant shift in thinking for tattoo culture. The industry has been moving towards increasingly complex machines, needles, and pigments for years, but the idea of reversibility has remained on the periphery – usually addressed through fading or laser removal. Here, reversibility is built directly into the ink’s chemistry, not the application technique or subsequent removal.
Testing on Themselves: A Lab Tradition
Nanoscience researcher Carson Bruns, one of the developers, didn’t limit himself to laboratory test tubes. According to him, testing the ink on his own skin has become “almost a tradition” for his team. Bruns spent twelve months applying the three dyes and their mixtures to his own leg, creating new colors. The resulting tattoos lasted for over two years, which is a significant period for an experimental pigment.
Previously, Bruns had already experimented with color-changing inks: he applied so-called “sun freckles” to himself – a design that darkens and turns blue as UV levels increase. This technique allowed for visual tracking of how much time the skin had spent in the sun, turning the tattoo into a kind of indicator.
Prospects and Limitations
The work is initially oriented towards medical scenarios – where it is important to temporarily mark the skin, rather than leave a permanent mark. However, the technology is not yet ready for a wide audience: before Phototat becomes available, testing on other people, not just the author, is necessary. This is a standard but mandatory step, without which no new pigment can leave the laboratory.
Nevertheless, the very fact that a tattoo can be made “switchable” changes the perception of what it means to be tattooed. Perhaps in a few years, inks will appear on the market that allow you to wear a design according to your mood or need, rather than for life. For tattoo culture, this opens up a whole layer of new forms – from temporary markers to interactive patterns that react to light.