Fabrication, Characterization, and Clinical Assessment of Ultrathin Skin-Conformable Tattoo Electrodes for ECG Monitoring

In recent years, there has been a surge in interest surrounding the advancement of gel-free, ultrathin, skin-conformable tattoo electrodes for continuous and extended monitoring of ECG signals. This development aims to mitigate the limitations associated with traditional electrodes. However, all of these results are limited to data from individual subjects. Hence, replicability is reduced by individual variability due to a small sample size, which may lead to inconclusive results. Consequently, the suitability of these outcomes for clinical validation has been inadequately investigated. In this study, an ultrathin, gel-free, skin-conformable PEDOT:PSS-based tattoo electrode was fabricated and characterized. A preclinical skin irritation test of the PEDOT:PSS-based tattoo electrode was performed before clinical assessment. Next, we accessed the performance of these tattoo electrodes involving 34 healthy volunteers and compared the ECG signals acquired from these ultrathin electrodes with those recorded by traditional Ag/AgCl electrodes. The fabricated tattoo electrode is approximately 10 μm thick and has a skin–electrode impedance of 72 KΩ at 50 Hz. The preclinical skin irritation study confirmed that the film of PEDOT:PSS is nontoxic, noncorrosive, and biocompatible with rabbit skin. In healthy volunteers, the data points from the sample population all cluster closely around the bias line, and we observed no significant systematic error associated with the ECG measurement. This PEDOT:PSS-based skin-conformal tattoo electrode retained its characteristics even after continuous wear for up to 24 h during routine activities, and the electrodes remained stable even after 60 days of storage. Altogether, our findings confirmed the suitability of these skin-conformal PEDOT:PSS-based tattoo electrodes for ECG monitoring.