The UmboMic: A PVDF Cantilever Microphone

TL;DR

The paper introduces the UmboMic, a PVDF-based microelectromechanical microphone designed for implantation in cochlear implants, demonstrating promising performance in cadaveric human temporal bones for future hearing aid applications.

Contribution

It presents a novel PVDF cantilever microphone with a low-noise amplifier, suitable for totally-implantable cochlear implants, with performance comparable to conventional hearing aid microphones.

Findings

Achieves 32.3 dB SPL input noise over 100 Hz to 7 kHz

Displays good linearity and flat frequency response from 100 Hz to 6 kHz

Demonstrates feasibility of PVDF-based microphone for implantable use

Abstract

Objective: We present the "UmboMic," a prototype piezoelectric cantilever microphone designed for future use with totally-implantable cochlear implants. Methods: The UmboMic sensor is made from polyvinylidene difluoride (PVDF) because of its low Young's modulus and biocompatibility. The sensor is designed to fit in the middle ear and measure the motion of the underside of the eardrum at the umbo. To maximize its performance, we developed a low noise charge amplifier in tandem with the UmboMic sensor. This paper presents the performance of the UmboMic sensor and amplifier in fresh cadaveric human temporal bones. Results: When tested in human temporal bones, the UmboMic apparatus achieves an equivalent input noise of 32.3 dB SPL over the frequency range 100 Hz to 7 kHz, good linearity, and a flat frequency response to within 10 dB from about 100 Hz to 6 kHz. Conclusion: These results demonstrate the feasibility of a PVDF-based microphone when paired with a low-noise amplifier. The reported UmboMic apparatus is comparable in performance to a conventional hearing aid microphone. Significance: The proof-of-concept UmboMic apparatus is a promising step towards creating a totally-implantable cochlear implant. A completely internal system would enhance the quality of life of cochlear implant users.