Light-emitting tattoo was first designed

Scientists at the UCL and the IIT – Istituto Italiano di Tecnologia (Italian Institute of Technology) have created a temporary tattoo with light-emitting technology used on TV and smartphone screens, paving the way for a new kind of ‘smart tattoo’ ‘with a range of potential uses.

The technology, which uses organic light emitting diodes (OLEDs), is applied in the same way as tattoos for water transfer. That is, the OLEDs are manufactured on temporary tattoo paper and transferred to a new surface by being pressed onto it and covered with water.

The researchers, who described the process in a new article in the journal Advanced electronic materials, says it can be combined with other tattoo electronics to radiate light if an athlete is dehydrated, or if we need to get out of the sun to prevent sunburn. OLEDs can be tattooed on packaging or fruit to indicate that a product’s expiration date is over or will soon become inedible, or can be used in the form of glowing tattoos.

Professor Franco Cacialli (UCL Physics & Astronomy), senior author of the article, said: “The tattooed OLEDs we showed for the first time can be made on a large scale and very cheaply. They can be combined with other forms of tattoo electronics for a very wide range of possible uses: it can be fashionable, for example to give glowing tattoos and fingernails with a light emission.In sports, it can be combined with a sweat sensor to indicate dehydration.

“In healthcare, they can emit light if there is a change in a patient’s condition – or if the tattoo is twisted into the skin the other way around, it could possibly be combined with light – sensitive therapies to target cancer cells, for example.

“Our proof of concept study is the first step. Future challenges will include plugging in the OLEDs as much as possible to prevent them from decaying quickly through contact with air, as well as integrating the device with a battery or supercapacitor. “

The OLED device developed by the researchers is a total of 2.3 micrometers thick (less than one 400th millimeter) – about a third the length of a single red blood cell. It consists of an electroluminescent polymer (a polymer that emits light when an electric field is applied) between electrodes. An insulating layer is placed between the electrodes and the commercial tattoo paper.

The light emitting polymer is 76 nanometers thick (a nanometer is a millionth of a millimeter) and was created using a technique called spin coating, where the polymer is applied to a substrate that is spun at high speed, which is a extremely thin and even layer.

After building the technology, the team installed the tattooed OLEDs, which emit green light, on a glass window, a plastic bottle, an orange and paper packaging.

Senior author Professor Virgilio Mattoli, a researcher at the Italian Institute of Technology, said: “Tattoo electronics is a fast-growing field of research. At the Italian Institute of Technology, we used to do pioneering work with the electrode we tattooed on people’s skin. which can be used to perform it. diagnostic tests such as electrocardiograms. The advantage of this technology is that it is inexpensive, easy to apply and use and easy to wash off with soap and water. “

OLEDs were first used in a flat screen TV 20 years ago. Some of the advantages of the technology are that it can be used on flexible, pliable surfaces and that it can be made from liquid solvents. This means they can be printed and provide an inexpensive way to create custom new OLED designs.