Electroluminescent tattoo designed for the first time

Scientists from UCL and IIT – Istituto Italiano di Tecnologia (Italian Institute of Technology) have created a temporary tattoo with electroluminescent 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 water transfer tattoos. Simply put, OLEDs are made on temporary tattoo paper and transferred to a new surface by being pressed on and dabbed with water.

The researchers, who described the process in a new article in the journal Advanced electronic materials, let’s say it could be combined with other electronic tattoo devices to, for example, emit light when an athlete is dehydrated or when we need to get away from the sun to avoid sunburn. OLEDs can be tattooed on packaging or fruit to signal that a product has passed its expiration date or will soon become inedible, or used for fashion in the form of glow tattoos.

Professor Franco Cacialli (UCL Physics & Astronomy), lead author of the article, said: “The tattooable OLEDs that we have demonstrated for the first time can be manufactured on a large scale and very inexpensively. They can be combined with other forms of tattoo electronics for a very wide range of possible uses. These could be for fashion – for example, providing glowing tattoos and light-emitting nails. could be associated with a sweat sensor to signal dehydration.

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

“Our proof-of-concept study is the first step. Future challenges will include encapsulating OLEDs as much as possible to prevent them from degrading rapidly upon contact with air, as well as integrating the device with a battery. or a supercapacitor. “

The OLED device developed by the researchers has a total thickness of 2.3 micrometers (less than a 400th of a millimeter), or about a third of 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 the 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 one millionth of a millimeter) and was created using a technique called spin coating, where the polymer is applied to a substrate which is spun at high speed, producing an extremely thin and uniform. layer.

Once the technology was built, the team applied the tattooable OLEDs, which emitted green light, to a pane of glass, a plastic bottle, an orange, and paper packaging.

Lead author Professor Virgilio Mattoli, researcher at the Italian Institute of Technology, said: “Tattoo electronics is a growing area of ​​research. At the Italian Institute of Technology, we have already developed electrodes which we have tattooed on people’s skin and which can be used for diagnostic tests such as EKGs. The advantage of this technology is that it is inexpensive, easy to apply and use, and washes easily with soap and water. “

OLEDs were first used in a flat screen TV 20 years ago. Among the advantages of the technology is the fact that they can be used on both flexible and flexible surfaces and that they can be made from liquid solvents. This means that they are printable which is an inexpensive way to create new bespoke OLED designs.