Abstract
With the rising need for on-body biometric sensing, the development of wearable electrophysiological sensors has been faster than ever. Surface electrodes placed on the skin need to be robust in order to measure biopotentials from the body reliably and comfortable for extended wearability. The electrical stability of nonpolarizable silver/silver chloride (Ag/AgCl) and its low-cost, commercial production have made these electrodes ubiquitous health sensors in the clinical environment, where wet gels and long wires are accommodated by patient immobility. However, smaller, dry electrodes with wireless acquisition are essential for truly wearable, continuous health sensing. Currently, techniques for the robust fabrication of custom Ag/AgCl electrodes are lacking. Here, we present three methods for the fabrication of Ag/AgCl electrodes: oxidizing Ag in a chlorine solution, electroplating Ag, and curing Ag/AgCl ink. Each of these methods is then used to create three different electrode shapes for wearable application. Bench-top and on-body evaluation of the electrode techniques was achieved by electrochemical impedance spectroscopy (EIS), calculation of variance in electrocardiogram (ECG) measurements, and analysis of auditory steady-state response (ASSR) measurement. Microstructures produced on the electrode by each fabrication technique were also investigated with scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The custom Ag/AgCl electrodes were found to be efficient in comparison with standard, commercial Ag/AgCl wet electrodes across all three of our presented techniques, with Ag/AgCl ink shown to be the better out of the three in bench-top and biometric recordings.
Highlights
There is a variety of electrophysiological signals from the body that help give inference about the patient’s condition
Three shapes were made for the Ag/AgCl electrodes: bullet, rod, and disc, potentially suited for different sensing locations including chest, scalp, and inear
The study indicates that the ink performed the best out of the three fabrication methods followed by bleach and electroplating in the saline and skin electrochemical impedance spectroscopy (EIS)
Summary
There is a variety of electrophysiological signals from the body that help give inference about the patient’s condition. Such information can be valuable in diagnosing and treating various illnesses (Kamarajan and Porjesz, 2015). Symptom onset can be triggered by environmental factors outside of professional care. Wearable electrophysiological sensing is useful for researchers and medical professionals to monitor the patient’s health and wellness in various environmental conditions (Bonato, 2010; Borhani et al, 2021). In order for the recordings to be a reliable reference for diagnosis and study, electrodes with a good contact and signal quality are needed. Conventional electrodes used for electrophysiological measurements are based on an electrolytic gel to bridge
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