Thin Film PZT Acoustic Sensor for Fully Implantable Cochlear Implants

Abstract

This paper presents design and fabrication of a MEMS-based thin film piezoelectric transducer to be placed on an eardrum for fully-implantable cochlear implant (FICI) applications. Resonating at a specific frequency within the hearing band, the transducer senses eardrum vibration and generates the required voltage output for the stimulating circuitry. Moreover, high sensitivity of the sensor, 391.9 mV/Pa @900 Hz, decreases the required power for neural stimulation. The transducer provides highest voltage output in the literature (200 mVpp @100 dB SPL) to our knowledge. A multi-frequency piezoelectric sensor, covering the daily acoustic band, is designed based on the test results and validated through FEA. The implemented system provides mechanical filtering, and mimics the natural operation of the cochlea. Herewith, the proposed sensor overcomes the challenges in FICI operations and demonstrates proof-of-concept for next generation FICIs.

Fully Implantable Cochlear Implant Interface Electronics With 51.2-$\mu$ W Front-End Circuit

“…Size of the sensor is adjusted to be 5×5 mm 2 which can be implanted on the eardrum or on the umbo at middle ear [29], [30]. The fabrication process of the sensor is similar to the one explained in [31]. Moreover, a more compact design that fits eight PZT sensors to the volume of the middle ear has been proposed in [24].…”

Piezoelectric Composites and their Applications

“…These implants are generally considered as the treatment of severe-to-profound sensor in hearing loss. Although new technologies for cochlar implants are available to cure deafness, even the new developed fully implantable CIs (FICIs) are not compatible with water, high ambient noise and consume more power which demands frequent recharging [59]. Also FICIs demands ultra-low-power audio processing and energy-efficient neural stimulation.…”

Piezoelectric Materials for Medical Applications

“…The destruction of inner ear cells results in severe hearing loss and is most commonly treated by cochlear implants. Though the current technology allows for recovery from deafness, it is incompatible with water and has very high-power requirements [81]. Piezoelectric materials can be used for creating an artificial basilar membrane (ABM).…”

“…Varying physical rigidity and thickness of the basilar membrane allows it to perform its duty, and likewise piezoelectric materials can filter out frequency based on their physical properties [82]. Ceramics, such as PZT or AlN films, can be fabricated in beam or cantilever arrays with lengths corresponding with different resonance frequencies [81,83]. Alternatively, devices based on PVDF or P(VDF-TrFE) membranes have been fabricated [47,[83][84][85].…”