Electrode Comparison for Heart Rate Detection via Bioimpedance Measurements

Compact wrist-worn devices that can continuously measure human bio-parameters such as heart rate offers valuable health information and facilitate healthcare outside clinical settings. Bioimpedance is a promising alternative sensing modality for vital signs monitoring in wearable devices but requires close proximity to the subject's skin. The current study evaluates the suitability of different types of electrodes for on-wrist heartrate measurements via bioimpedance. We compare copper, gold, and stainless steel electrodes with smooth and bumpy surfaces. To this end, we develop a signal-to-heart-rate data processing pipeline and a SNR-based metric that algorithmically evaluates the signal's quality. The results show that while there is a clear trend in the data that supports the selection of stainless steel over other metals and bumpy over smooth electrode surfaces, most of the variance in the signal quality comes from factors other than the electrode type.