Printed Tattoo Electrodes Revolutionize Brain Signal Measurement

A team of researchers led by Francesco Greco developed inkjet-based “tattoo electrodes” which are not only compatible for EMG, ECG and EEG but also the world’s first dry electrodes qualified for monitoring brain activities via MEG.

© Greco - TU Graz

Header Picture © Greco – TU Graz

Back in 2015, a research team under the leadership of Francesco Greco, head of the Laboratory of Applied Materials for Printed and Soft electronics (LAMPSe) at the Institute of Solid State Physics at Graz University of Technology, developed conductive polymers that are printed on tattoo paper with an inkjet printer and then applied to the skin in order to measure heart or muscle activity. These so-called tattoo electrodes were groundbreaking in the field of electrophysiological examinations. This is because they need no liquid interface, are about 100 times thinner than a human hair, and thus, perfect for long-term measurements.

Ready for an Update

After a first optimization in 2018, Greco and his colleagues Esma Ismailova (Department of Bioelectronics, École Nationale Supérieure des Mines de Saint-Étienne, France) and Laura Ferrari (The BioRobotics Institute, Scuola Superiore Sant’Anna, Italy) have now set another milestone as the new modified electrodes can be used to measure not just heart and muscle but also brain activity.

“Brain waves are in the low frequency range and EEG signals have a very low amplitude. They are much more difficult to capture in high quality than EMG or ECG signals,”

explains Laura Ferrari.

So the team had to find a way to optimize the connection between skin and electrode. The solution was an approach involving the adaption of composition and thickness of the transfer paper and the coating of a conductive polymer on tattoo paper with an inkjet printer.”Due to inkjet printing and the commercially available substrates, however, our tattoos are significantly less expensive than current EEG electrodes and also offer more advantages in terms of wearing comfort and long-term measurements in direct comparison,” explains Greco.

The new tattoo electrodes were tested under real clinical conditions and proved to be as reliable and effective as common EEG electrodes.

“Due to inkjet printing and the commercially available substrates, however, our tattoos are significantly less expensive than current EEG electrodes and also offer more advantages in terms of wearing comfort and long-term measurements in direct comparison,”

says Greco.

The First-Ever Dry MEG Electrodes

But this is not the end of the story: The innovative electrodes are not only the first dry electrodes qualified for long-time EEG measurement, but they are also the first that allow for use in magneto-encephalography (MEG). In common, only wet electrodes, using gel or an electrode paste, enable monitoring brain activities with MEG. While currently figuring out how to use this technology in clinics, neuroengineering or brain computer interfaces, Greco already knows:

“With our method, we produce the perfect MEG-compatible electrode while reducing costs and production time.”

Do you know other good examples for the use of print technologies in clinical fields? We’re looking forward to your suggestions.