Scientists develop tattoos you can turn on and off

A tattoo you can turn on and off sounds like science fiction, but a team of engineers has brought it into reality.

A new study in Cell Press journal Matter and Light reveals the new inks could help people conceal their tattoos when they feel the need, such as for a job interview.

“Tattooing is a very ancient technology that remains mostly untapped as a platform for today’s technologies,” lead author Carson Bruns of the University of Colorado said.

The new inks, known as PhotoTat, are made from dyes and a plexiglass-like material common in many medical technologies on the market today, including dermal fillers.

The research is a passion project for Bruns, who has a lot of his own tattoos, including a green lion on his arm.

“I love body art because of how personal it is,” he says.

To make the inks, Bruns and his colleagues start with a material called polymethyl methacrylate, or PMMA, which forms tiny spheres that look like they’re made of glass.

The team then inserts a range of colour-changing dyes into the spheres.

“By mixing these primary colours, we can generate a full colour image,” Bruns says.

Normally, these dyes are completely invisible to the human eye.

But when put under an ultraviolet light on them, the authors say they change colour in a matter of seconds - turning a vibrant blue, magenta, or yellow.

The colours fade over several hours, but you can also switch them off faster by exposing them to a bright LED light.

“PhotoTat is like a switch. You turn it on with UV light, but you can turn it off again when you go to grandma’s house,” Bruns said.

The technology remains off the market, and Bruns said it’s yet not determined whether the inks are safe for humans - though he has experimented on himself as the research continues.

Beyond cosmetics, Bruns also said there might be practical applications for the technology, such as for people undergoing radiation therapy.

Such patients often have to get small tattoos to guide radiation beams, which can be both physically and mentally scarring.

“They’re not beautiful, and they become a permanent reminder of a traumatic experience,” Bruns said.

“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’s own PhotoTat designed include black outline of fish scales on his leg, which he’s filled in with PhotoTat inks and compares to “magical mermaid scales”.

“There’s a stigma, in science and in many cultures, around body art,” Bruns said.

“I’m proud to be pushing against that.”