Scientists Create Tattoos You Can Turn On and Off With Light

Imagine having a tattoo that vanishes whenever you want it to, then reappears with a flash of light.

Carson Bruns at the University of Colorado has been living with exactly that for the past two years. His fish scale tattoo can switch on and off, and he says it hasn't faded a bit.

The technology, called PhotoTat, uses special dyes that change from invisible to colored when exposed to certain wavelengths of light. Ultraviolet light makes the tattoo appear, while bright visible light erases it again.

"You can simply turn the tattoo off whenever you don't want to see it and it disappears from view," says Bruns. The tattoo itself stays permanently in your skin, but you control when anyone can actually see it.

The application process looks identical to traditional tattooing. Artists use the same machines and needles to implant the pigment particles into the dermis layer of skin.

The only difference is the ink itself. Traditional pigments stay one color forever, while these photochromic dyes cycle between visible and invisible states repeatedly.

The team has developed 16 distinct colors with at least 300 different shades. White remains impossible because it reflects rather than absorbs light, and they haven't quite cracked true cyan yet.

The Ripple Effect

Cancer patients receiving radiation therapy often get permanent tattoos to guide treatment beams. These medical markings can serve as unwanted reminders long after recovery.

PhotoTat could change that completely. Patients would still get the precision guidance doctors need, but the marks would disappear once treatment ends.

Beyond medicine, the technology offers creative freedom artists have never had before. Someone could display different designs for different occasions, or simply take a break from their ink without commitment.

There are practical considerations. Wearers need sunscreen to prevent accidental activation outdoors, and blue ink gradually develops a faint purple tint over many cycles.

Safety testing still needs completion before public availability. The polymer coating the dyes has proven safe in medical implants, though the dyes themselves require further study.

Tattoo expert Signe Bedsted Clemmensen notes that any foreign substance in the body carries potential risks, visible or not. Recent research has linked some traditional inks to immune system effects and rare reactions.

After two years with his switchable fish scales, Bruns reports zero side effects and plenty of compliments. The technology transforms tattoos from permanent statements into flexible forms of self expression.