Abstract
This paper presents a multi-channel acoustic transducer that works within the audible frequency range (250-5500 Hz) and mimics the operation of the cochlea by filtering incoming sound. The transducer is composed of eight thin film piezoelectric cantilever beams with different resonance frequencies. The transducer is well suited to be implanted in middle ear cavity with an active volume of 5 mm <inline-formula> <tex-math notation="LaTeX">$\times5$ </tex-math></inline-formula> mm <inline-formula> <tex-math notation="LaTeX">$\times0.62$ </tex-math></inline-formula> mm and mass of 4.8 mg. Resonance frequencies and piezoelectric outputs of the beams are modeled with Finite Element Method (FEM). Vibration experiments showed that the transducer is capable of generating up to 139.36 mV<inline-formula> <tex-math notation="LaTeX">$_{{\mathrm {pp}}}$ </tex-math></inline-formula> under 0.1 g excitation. Test results are consistent with the FEM model on frequency (97%) and output voltage (89%) values. Device was further tested with acoustic excitation on an artificial tympanic membrane and flexible substrate. Under acoustic excitation, 50.7 mV<inline-formula> <tex-math notation="LaTeX">$_{{\mathrm {pp}}}$ </tex-math></inline-formula> output voltage generated under 100 dB Sound Pressure Level (SPL). Output voltages observed in acoustical and mechanical characterizations are the highest values reported to the best of our knowledge. Finally, to assess the feasibility of the transducer in daily sound levels, it was excited with a speech sample and output signal was recovered. Time-domain waveforms of the recorded and recovered signals showed close patterns.
Highlights
OUR ears are magnificent organs that enable us to perceive ambient sounds from the faintest flapping of an insect to the extremely loud roaring of spacecraft launch through the hearing chain: eardrum, ossicles, and the cochlea
In order to implement the transducer with given restrictions, we modeled the structure with Finite Element Analysis software COMSOL Multiphysics
A thin film piezoelectric multichannel acoustic transducer for Fully Implantable Cochlear Implant (FICI) applications is designed with inspiration from ancient music instrument, fabricated by using MEMS methods, systematically characterized, and experimentally adapted for daily usage
Summary
OUR ears are magnificent organs that enable us to perceive ambient sounds from the faintest flapping of an insect to the extremely loud roaring of spacecraft launch through the hearing chain: eardrum, ossicles, and the cochlea. They make the ear the best acoustic sensor by providing broad frequency selectivity (20 Hz – 20 kHz) and dynamic range (0 – 140 dB SPL). Council (ERC) under the European Union's Horizon 2020 research and innovation programme under grant agreement No 682756. Muhammed Berat Yüksel is with the Department of Electrical and Electronics Engineering, MEMS Research and Application Center, Middle East Technical University, Ankara, Turkey
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