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University College London, United Kingdom, and the Italian Institute of

University College London, United Kingdom, and the Italian Institute of Technology, Genova, Italy

Researchers have developed a temporary tattoo that uses organic light-emitting diodes (OLEDs) and is applied in the same way as water-transfer tattoos. The OLEDs are fabricated onto temporary tattoo paper and transferred to a new surface by being pressed onto it and dabbed with water.

It could be combined with other tattoo electronics to, for instance, emit light when an athlete is dehydrated or when we need to get out of the Sun to avoid sunburn. OLEDs could be tattooed on packaging or fruit to signal when a product has passed its expiration date or will soon become inedible, or used for fashion in the form of glowing tattoos.

The tattooable OLEDs can be made at scale and very cheaply. They can be combined with other forms of tattoo electronics for a wide range of possible uses. In healthcare, they could emit light when there is a change in a patient's condition or, if the tattoo was turned the other way into the skin, they could potentially be combined with light-sensitive therapies to target cancer cells, for instance.

Future challenges for the team will include encapsulating the OLEDs as much as possible to stop them from degrading quickly through contact with air as well as integrating the device with a battery or supercapacitor.

The OLED device is 2.3 micrometers thick in total — 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) in between electrodes. An insulating layer is placed in between the electrodes and the commercial tattoo paper.

The light-emitting polymer is 76 nanometers thick and was created using a technique called spin coating, where the polymer is applied to a substrate that is spun at high speed, producing an extremely thin and even layer.

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

The tattoo is low-cost, easy to apply and use, and washes off with soap and water.

For more information, contact Mark Greaves at This email address is being protected from spambots. You need JavaScript enabled to view it.; +44 (0) 7990 675947.

This article first appeared in the October, 2022 issue of Tech Briefs Magazine.

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