Highly Stretchable and Breathable Dry Bioelectrode with Low Impedance for Electrophysiological Monitoring

Abstract

The high impedance caused by the lack of interfacial hydrogel in dry electrodes seriously affects the quality of acquired electrophysiological signals. Although there are existing strategies to reduce impedance with micro–nanostructures, achieving stretchable and breathable electrodes while ensuring low impedance is extremely challenging. Herein, we successfully prepared a dry textile electrode (nanomesh film (NF)-ZnO–polypyrrole (PPy)) with low impedance, high stretchability, and breathability. Wrinkle-nanorod coupled microstructures are constructed to increase the effective surface area and roughness of NF-ZnO–PPy electrode, achieving an exponential reduction in impedance compared with the smooth textile dry electrode (15.64 kΩ·cm⁻² at 10 Hz, approximately 1/6 of the lowest impedance of reported electrodes). Simultaneously, the wrinkled structure formed by pre-stretching improves electrode’s stretchability (up to 910% strain) and cycle stability (R/R₀ is within 1.08 after 1000 cycles at 30% strain). Furthermore, the NF-ZnO–PPy electrode has excellent breathability (2233.52 g·m⁻²·d⁻¹) and good biocompatibility. Finally, as a proof of concept, the 16-channel NF-ZnO–PPy electrode can record electromyography signals in different states and parts of body for a long time ((22.03 ± 0.76) dB, which is twice that of the commercial electrode). Notably, we employ ZnO nanorods as a template to reduce impedance. This template strategy overcomes complex and expensive micro–nanomanufacturing technologies (photolithography, laser processing, etc.) and can be suitable for most flexible substrates, showing great potential in the field of soft electronics.

Graphical Abstract