Tattoos are generally considered a form of personal expression, but a team of researchers in Europe have created what they are calling the world’s first light-emitting tattoo based on OLED screen technology that, in addition to seemingly cool, can also serve as a visible warning about potential health problems.
Tattoos are used by people to show their devotion to a long-defunct brand of MP3 player or to let everyone know how much they love their mothers. But there is also a precedent for tattoos to be used as a medical tool. Cancer patients undergoing radiation therapy are tattooed with small dots that are used as reference marks to accurately target machines used for treatments during repeated sessions, for example.
The idea of personally enhancing the skin of someone with shiny art is also not new, but previously it involved biohackers deploying technologies like LEDs under the skin, and the results don’t have much practical use other than drawing attention or inviting questions about why someone would do this to themselves. This new approach to light-emitting tattoos is easier to apply, more practical and temporary – without the need for surgery to remove it.
In an article recently published in the magazine Advanced Electronic Materials, “Ultra-thin, ultra-conformable, tattoo-free organic light-emitting diodes, ” scientists from University College London in the United Kingdom and the Italian Institute of Technology detail how their new approach to tattoos depends on the same organic light-emitting diode technology present on devices like newer iPhones, as well as the recent crop of mobile devices with foldable screens. The flexibility of an OLED display is important for this application, since human skin is very flexible and flexes and folds as the body moves.
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The real electronics of light-emitting tattoos, made of an extremely thin layer of an electroluminescent polymer that glows when a charge is applied, measures just 2.3 micrometers in thickness, which, according to the researchers, is about a third the diameter of a red blood cell. The polymer layer is then sandwiched between a pair of electrodes and sits on an insulating layer, which is glued to the temporary tattoo paper through a printing process that is not prohibitively expensive. Tattoos can be easily applied to surfaces using the same wet transfer process as temporary tattoos designed for children and can be easily washed when they are no longer needed or desired using soap and water.
With a current applied, OLED tattoos in their current form simply glow green, but they can eventually produce any color using the same RGB approach that OLED screens use. However, while researchers recognize that the potential for shiny tattoos exists, taking this art in a whole new direction, they also see even more potential for them as a medical tool. When combined with other wearable technologies, light-emitting tattoos can begin to flash when an athlete needs to rehydrate or change color when applied to food, providing obvious warnings when expiration dates have expired.
But don’t stroll at your local tattoo parlor and demand one of those new shiny tattoos yet. Researchers have so far successfully applied them to surfaces such as glass, plastic bottles, paper and even oranges, but human skin poses a greater challenge, given how much humans are constantly moving. OLED polymers can also degrade quickly when exposed to air, requiring additional layers to encapsulate and adequately protect them, and there is an even greater problem of finding a way to power them using tiny batteries or supercapacitors, as so far in the lab they’ve been connected to an external power supply and it’s doubtful if anyone wants to connect a USB power cable to the ink in their arms.