University of Colorado Boulder engineers have created a line of designer tattoo inks that stay invisible until wearers use different light wavelengths to activate and deactivate them, merging a 5,000-year-old art form with cutting-edge science.
The research team behind the light-activated invisible tattoos said the technology could let people turn their tattoos off for important business functions, then reactivate them in their personal lives. They also noted that the approach could allow people to “doodle on their own skin” using a standard laser pointer, or offer an invisible alternative to radiation treatment tattoos.
While not currently commercially available, the UC Boulder team said they hope their ongoing improvements will make the light-activated invisible tattoo technology available to artists worldwide in the coming years.
“Humans have been using the same tattooing technologies for thousands of years,” the University’s website explains. “It’s time for an upgrade.”
Light-Activated Invisible Tattoos Add New Twist to 5,000-Year-Old Art Form
Humans have intentionally marked their skin with permanent ink for thousands of years. The earliest confirmed tattoos were found on the surprisingly well-preserved skin of an ancient individual, known today as Ötzi the Iceman. His death on a frozen mountainside in the European Alps provided researchers a rare look into a 5,000-year-old world, including the oldest known evidence for tattooing.
Although the 61 tattoos found on Ötzi’s epidermis consisted of simple parallel lines and crosses, tests confirmed they were made about 5,300 years ago by slicing the skin and rubbing the wound with charcoal. Still, according to the lead author of the study detailing the new invisible tattoo technology, UC Boulder’s Carson Bruns, modern technology hasn’t begun to explore the ancient artwork’s full potential.
“Tattooing is a very ancient technology that remains mostly untapped as a platform for today’s technologies,” Bruns explained, adding that he loves body art “because of how personal it is.”
Given this passion for tattooing, which includes several tattoos of his own, the researcher and colleagues explored the possibility of customized light wavelengths to activate and deactivate tattoos depending on one’s current preference.
Generating a Full-Color Image with Ultraviolet Light
Instead of standard tattoo ink, Bruns’ team developed its own custom invisible tattoo ink from commercially available materials. The base material, called polymethyl methacrylate (PMMA), forms tiny transparent spheres that look similar to glass.
To create invisible tattoo ink in several colors, the team injected different dyes into the PMMA spheres. Bruns said that combining several colors allows the team to “generate a full color image,” depending on the artist’s preference.
Unlike normal tattoo inks, the dyes the UC Boulder team used are invisible to the human eye. However, the researchers note that when these dyes, which they have named “PhotoTat,” are exposed to light, they change color “in a matter of seconds.” Critically, the blue, magenta, and yellow hues fade after several hours and remain invisible until they are reactivated by the correct light wavelengths.
“PhotoTat is like a switch,” Bruns explained. “You turn it on with UV light.”
If a person with invisible tattoos doesn’t want to wait for them to fade naturally, the team said they can also turn them off more quickly using a bright LED light source.
“You can turn it off again when you go to grandma’s house,” Bruns explained.
Eliminating Traumatizing Permanent Reminders of Radiation Therapy
When discussing possible uses beyond artistic expression, Bruns and colleagues said their invisible tattoos could replace the small yet permanent ones many radiation therapy cancer patients get to help medical practitioners accurately guide the radiation beams. Although small, these visible markers can be mentally and physically scarring.
“They’re not beautiful, and they become a permanent reminder of a traumatic experience,” Bruns explained.
With their technology, the UC Boulder team said those tattoos could be available when needed and hidden from sight the rest of the time.
“With PhotoTat, we could turn an involuntary medical tattoo into something that’s only visible to the doctor when you go in the clinic, and then it can be invisible the rest of the time,” Bruns explained.
Making PhotoTat Commercially Available & Pushing Against the Stigma
Although the PMMA material used to make PhotoTat is commonly used in several approved medical technologies including dermal skin fillers, the research team said they still need to determine the ink’s safety profile.
Nonetheless, the undaunted Bruns said he has already embedded several invisible, colored tattoos within the permanently visible monochrome fish scale tattoos already on his leg, resulting in full color, “magical mermaid scales” he can turn on and off with light.
Currently in the laboratory stages, the UC Boulder team said they will spend the next few years improving their current designs. Once completed, the team said they hope to eventually make the inks for invisible tattoos “available for fans of body art across the country.”
Beyond the scientific, technological, and medical benefits of their work, Bruns said the effort also supports his broader, personal views on the conflicts that can arise between this millennia-old practice and modern-day critics.
“There’s a stigma, in science and in many cultures, around body art,” he explained. “I’m proud to be pushing against that.”
Christopher Plain has spent the last six years as Associate News Editor and Head Science Reporter at The Debrief. Follow and connect with him on X, learn about his novels at plainfiction.com, or email him at christopher@thedebrief.org.