Characterization of a novel polypyrrole (PPy) conductive polymer coated patterned vertical CNT (pvCNT) dry ECG electrode

Abstract

Conventional electrode-based technologies, such as the electrocardiogram (ECG), capture physiological signals using an electrolyte solution or gel that evaporates shortly after exposure, resulting in a decrease in the quality of the signal. Previously, we reported a novel dry impedimetric electrode using patterned vertically-aligned Carbon NanoTubes (pvCNT) for biopotential measurement applications. The mechanical adhesion strength of the pvCNT electrode to the substrate was weak, hence, we have improved this electrode using a thin coating of the conductive polymer polypyrrole (PPy) that strengthens its mechanical properties. Multiwall CNTs were grown vertically on a circular stainless-steel disc (ϕ= 10 mm) substrate of 50 μm thickness forming patterned pillars on a square base (100 μm × 100 μm) with an inter-pillar spacing of 200 μm and height up to 1.5 mm. The PPy coating procedure involves applying 10 μL of PPy mixed with 70% ethyl alcohol solution and rapid drying at 300 °C using a hot air gun at a distance of 10 cm. A comparative study demonstrated that the coated pvCNT had higher impedance compared to a non-coated pvCNT but lower impedance compared to the standard gel electrode. The PPy-coated pvCNT had comparable signal capture quality but stronger mechanical adhesion to the substrate.