Flexible Composites Based on PEDOT:PSS for Environmentally Friendly Electrocardiography Electrodes

Wearable electrodes have attracted attention for their ability to monitor human electrophysiological signals, such as those generated by the heart and captured via electrocardiography (ECG). In this study, an easy and scalable drop-coating method was used to develop flexible, dry, and sustainable ECG electrodes composed of a poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS)/polyvinyl alcohol/xanthan gum (PXP) composite. The electrodes were fabricated on different cellulosic substrates, such as Xuan paper, Kraft paper, and wheat bagasse, and further modified through the incorporation of MoO3 (PXPM composite). PXP exhibits a broad absorption band of 350–550 nm, while PXPM shows a shifted band of 400–750 nm, due to the interaction of MoO3 with PEDOT:PSS. The fluorescence emission of PXP appears at 443 nm, while the emission for PXPM is broader and centered at 437 nm. Electrically, both composites exhibit continuity and ohmic behavior. Microstructural analysis revealed that the interaction between the composite film and the substrate strongly influences pore formation, film uniformity, and the distribution of Mo species, highlighting the role of MoO3 as an interfacial modifier that promotes smoother and more homogeneous coatings on selected cellulosic substrates. All fabricated electrodes demonstrated the capability to detect ECG signals with sufficient quality to be clinically valid.