Development of piezoelectric oscillator sensor for in vivo monitoring of capsule formation around soft-tissue implants

Two types of piezoelectric wafer active sensor (PWAS) oscillators, Colpitts-type PWAS oscillator and series-type PWAS oscillator, designed for in-vivo monitoring of capsule formation around soft tissue implants have been presented. Both of the oscillators were explored analytically and experimentally. Colpitts-type PWAS oscillator uses the inductive property of the PWAS in its resonant frequency range and operates at the first resonant frequency of the PWAS. However, it is too sensitive to the surrounding damping. Therefore, it may not be an appropriate candidate for in-vivo application. For the series-type PWAS oscillator, some preliminary experiments showed that this type of oscillator can tell the difference in viscosity/damping conditions of different media. More work, such as calibration of output of the oscillator, needs to be done before using it in in-vivo monitoring of capsule formation. Keyword: piezoelectric wafer active sensor, bio-PWAS, PWAS oscillator, implant, in vivo, capsule formation