Inkjet-printed electrode ‘tattoos’ transmit perfect signals for days, study finds

When a patient is diagnosed using an electrocardiogram (ECG) or electromyography (EMG), they are required to wear electrodes on their body to transmit tiny electric impulses from the body to a computer, typically ‘gel electrode’.

These electrodes, although not large, are stiff and difficult for the patient to ignore, particularly as they can restrict movement. Given that the gel used on the electrode dries out quickly, this type of electrode cannot be used to monitor a patient for extended periods of time.

In order to provide a means for clinicians to perform long-term medical diagnosis, a team of researchers at TU Graz, working with international collaborators, have developed a printed electrode which can be worn comfortably on the skin and monitor the heart or muscles.

This approach was inspired by the temporary tattoos; the cheap, cheerful designs popular among tweens, which can be transferred from a sheet to the skin using water. The scientists printed conductive polymers onto conventional temporary tattoo paper, allowing them to produce different sizes and arrangements incorporating single or multiple electrodes. The external connections required to transmit signals from the body to a computer are also included within this polymer ‘tattoo’.

“With this method we have managed to take a big step forward in further developing epidermal electronics. We are on a direct road to making an extremely economical and simple, as well as versatile, applicable system which has enormous market potential,” said Dr Francesco Greco, a materials scientist at TU Graz.

These tattoo electrodes are less than one micrometre thick, allowing them to be applied to the uneven surface of human skin anywhere on the body; this has proved a challenge for devices intended to be worn on the skin. Even when pierced – accidentally or with the growth of a hair – the electrode will continue to function. This could allow them to be used for much longer-term applications than existing wearable devices: studies have demonstrated that perfect transmission is possible for up to three days.

According to the researchers, the electrodes are barely perceptible by the wearer. For even greater comfort, different electrodes could be printed for different parts of the body.

According to the researchers, these tattoo electrodes could also prove useful for stimulating certain parts of the body with small electrical signals. Electrostimulation is used in some forms of physiotherapy.

“Not only could we measure impulses using this method, but we could also stimulate body regions in a targeted way,” said Greco.