MEMS based thin film piezoelectric multi-channel transducer for sensing and filtering ossicular vibration

Date

2023-11-24

Author

Yüksel, Muhammed Berat

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In this thesis, a middle ear implantable bilayer multi-frequency piezoelectric acoustic transducer for a fully implantable cochlear implant (FICI) concept was designed, modeled, fabricated, and tested. Transducer can be implanted on hearing chain to detect and filter the ambient sound in 8-frequency bands between 250 to 6000 Hz. The transducer design is conventional surgery compatible. The structure is formed with 3×3×0.36 mm3 active space for each layer and 5.2 mg total active mass, excluding packaging. Characterization of the transducer was carried on an artificial membrane whose vibration characteristic is similar to umbo vibration. On the artificial membrane, piezoelectric transducer generates up to 320.3 mVpp under 100 dB SPL excitation and covers audible acoustic frequency. The measured signal-to-ratio of the channels is up to 84.2 dB. Sound quality of the transducer was graded with an objective qualification method, PESQ, for the first time in the literature, to the best of our knowledge, and scored 3.42/4.5. Output voltages observed in acoustical characterizations are the highest values reported in the literature. Thus, system considers a wide range of sound detection and compatibility with a signal conditioning circuit. Finally, outputs were processed by a current mode low-power signal conditioning circuit that stimulates the auditory neurons through intracochlear electrodes. The FICI was validated with an in-vivo model where electrical auditory brainstem response (eABR) of the animal was observed while applying sound excitation. The eABR results demonstrate that the system can evoke responses in the auditory nerves of guinea pig for sound range of 45-100 dB.

Subject Keywords

Transducer, MEMS, Fully Implantable Cochlear Implant, Piezoelectric, Animal Model

URI

https://hdl.handle.net/11511/106380

Collections

Graduate School of Natural and Applied Sciences, Thesis