5H-2 A Piezoelectric Membrane Sensor for Biomedical Monitoring

A piezoelectric membrane sensor, consisting of a metal foil, a piezoelectric ceramic film and a top electrode, has been developed. Thick lead zirconate titanate composite film was coated onto a stainless steel (SS) foil and a top electrode was formed using a silver paste. The SS foil served as the bottom electrode as well as the substrate. Due to the porosity in the piezoelectric film and the thin metallic membrane substrate, the high flexibility was realized. The porosity was observed by a scanning electron microscopy. This membrane sensor has been worked as a unimorph-type bending sensor as well as an ultrasonic sensor. Biomedical applications using this sensor were demonstrated. The sensor was directly attached onto a wrist and signals corresponding to arterial pulse waves have been successfully obtained. The signals had a signal-to-noise ratio of better than 20 dB. Breathing curves were also measured on a human belly. In addition, ultrasonic signal reflected from a finger bone was observed with a pulse-echo technique. Thus, this sensor could be used as a wearable sensor, which does not disturb daily life activities including sleeping, for real-time and continuous monitoring of personal health conditions