Wrist Pulse Recording With a Wearable Piezoresistor-Piezoelectret Compound Sensing System and Its Applications in Health Monitoring

Pulse signals contain abundant information which is useful in healthcare. Various approaches have been suggested with an aim of acquiring high-quality pulse signals, but are usually limited by either low accuracy or complicated apparatus. In this work, we proposed a "quasi applanation tonometry" method for pulse detection, where an adjustable static pressure was applied on wrist to compress artery and pulse signals were simultaneously recorded at the same position. To realize the method, a wearable compound sensing system, consisting of a piezoresistor and a piezoelectret sensor, was developed to measure the static pressure and pulse signals, respectively. The results showed that clear pulse signals with detailed information were successfully acquired with the sensing system, and by increasing the static pressure the pulse amplitude increased accordingly until a maximum was achieved. Further increase of the static pressure would lower the pulse amplitude and destroy the waveform gradually. A linear relation between the mean arterial pressure and the static pressure for maximum pulse amplitude was fitted, which would support the proposed method for the application of blood pressure estimation. In addition, heartbeat and respiration monitoring were also realized based on the recorded pulse signals. In general, this work has demonstrated a simplified pulse detection method by developing a piezoresistor-piezoelectret compound sensing system and realized some applications of pulse detection in health monitoring.