The long-term reliability of pre-charged CMUTs for the powering of deep implanted devices
Mart Saccher (TU Delft - Electronic Components, Technology and Materials)
Shinnosuke Kawasaki (TU Delft - Electronic Components, Technology and Materials)
Ronald Dekker (Philips Research)
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Abstract
Recently, focused ultrasound has been proposed to power deeply implanted medical devices. Almost exclusively, lead zirconate titanate (PZT) transducers are used to convert acoustic energy into electrical energy. Unfortunately, these lead containing devices cannot be hermetically encapsulated since that would block the ultrasound. We propose the use of biocompatible Capacitive Micromachined Ultrasonic Transducer (CMUT) elements to replace traditional PZT transducers. In addition, to eliminate the external bias voltage, we introduced a charge trapping Al2O3 layer inside the CMUT to create a built-in bias voltage. These devices can be pre-charged and used as a receiver for US power. In this work, the viability of charged CMUTs to power deep implants was explored by investigating the effect of the charging parameters and by performing Accelerated Lifetime Tests (ALT). The estimated lifetime at body temperature ranges between 2.5 to 3.5 years at body temperature, which significantly depends on the charging parameters.