Flexible, Adhesive Dry Electrodes with Bio-Inspired Microstructures for Improved Electrophysiological Signal Acquisition in Maternal Health

Soft electronic devices and sensors have seen substantial interest devoted to them for the purpose of recording and analyzing various electrophysiological signals including for the use of electrocardiography (ECG), electromyography (EMG), and electroencephalography (EEG). Dry electrodes specifically have enormous potential compared to traditional commercial electrodes for long-term, real-time monitoring of biopotential activity. Gel-based commercial electrodes have notable drawbacks such as limited flexibility, skin irritation that decreases comfort, inconsistent signal quality due to poor conformal contact, and degraded signal quality over long-term monitoring due to drying out.
Herein, we report a flexible, dry PEDOT:PSS-based electrode that uses a dual-method adhesion system based on chemical additives and bio-inspired microstructures to collect stable, low-noise electrophysiological signals through a low-cost fabrication process. Dry electrodes fabricated with poly(3,4-ethylenediox-ythiophene) polystyrenesulfonate (PEDOT:PSS) as a conductive polymer offer such advantages as the ability to conform to skin deformations, a lighter weight than traditional electrodes, reduction of motion artifacts, and improved comfort all without the use of gel; the absence of gel negates issues previously mentioned such as skin irritation or having the electrode dry out. Furthermore, PEDOT:PSS-based electrodes have tunable stretchability, conductivity, and adhesion properties that are optimal for flexible bioelectronics and wearable devices.
First, a solution comprised of PEDOT:PSS, ethylene glycol (EG), polyethylene oxide (PEO), polyvinyl alcohol (PVA), and tannic acid (TA) is prepared. PVA has numerous hydroxyl (-OH) groups and relatively high surface energy that improves it wetting properties and adhesion. TA has hydroxyl groups as well that promote adhesion and benzene rings that can adhere to hydrophobic surfaces. Second, the solution is cured in a mold that produces a surface pattern inspired by microstructures found on reptilian appendages to further promote adhesion. These electrodes can record reliable, clean biopotential signals with an increased signal-to-noise (SNR) ratio than traditional electrodes. This electrode’s capability for maternal health in a clinical setting was also demonstrated through monitoring uterine contraction signals from a patient in labor. Our flexible and adhesive novel dry electrode is a promising alternative to commercial electrodes due to its low-cost manufacturing, adhesive properties, comfortability, and improved signal strength of biopotential activities.