Self-Powered Wearable Micropyramid Piezoelectric Film Sensor for Real-Time Monitoring of Blood Pressure

Cardiovascular diseases can be prevented in advance by noninvasive and continuous real-time measurement of blood pressure using a wearable sensor. Among many recent developments, piezoelectric sensors demonstrate the possibility to monitor blood pressure continuously without relying on an external energy input. However, most of the piezoelectric-sensor research focuses on the property enhancement of piezoelectric materials without systematic investigations of how sensor performance is influenced by the microgeometry and electrode configuration of piezoelectric sensor. Herein, the micropyramid-assisted piezoelectric film (MPF) sensors are designed and constructed and their performances are investigated both experimentally and by finite-element modeling (FEM) simulations. The sensor signal that is strongly coupled to both stress amplification and capacitance change because of the micropyramids and electrode configuration is identified. After comparing the different designs of MPF sensors, it is confirmed that polydimethylsiloxane micropyramids covered with the highly compliant Ecoflex show the highest sensitivity. The MPF sensor shows the sensitivity of 685 mV N-1 in a range between 50 and 400 mN. MPF sensors are attached to the wrist and neck to measure pulse pressure signals. Using the pulse pressure signals and linear regression, blood pressures are estimated and compared with the values measured with a commercial cuff device.