The UmboMic: Characterization and Testing of a Middle Ear Microphone.

Area of Science:

• Biomedical Engineering
• Materials Science
• Audiology

Background:

• Fully implantable cochlear implants represent the future of hearing restoration technology.
• Internal microphone implantation aims to enhance device performance and user experience.

Purpose of the Study:

• To report developments on the "UmboMic," a piezoelectric microphone specifically designed for fully implanted cochlear implants.
• To assess the feasibility and performance of the UmboMic for internal auditory applications.

Main Methods:

• The UmboMic utilizes the piezoelectric effect with polyvinylidene difluoride (PVDF) layers to detect umbo motion in the middle ear.
• Material modifications were made to enhance biocompatibility, including changes to conducting and glue layers.
• Seven UmboMic sensors were bench-tested and subsequently implanted in five human cadaveric ears.

Main Results:

• The UmboMic exhibits high sensitivity across frequencies, a low noise floor, electromagnetic interference shielding, and good linearity.
• Performance is comparable to external hearing-aid microphones, with an equivalent input noise of 32.4 dB SPL (100 Hz–7 kHz).
• Fabrication repeatability showed less than a 6 dB difference in sensor sensitivity, and positioning studies indicated resilience to implantation variations.

Conclusions:

• The UmboMic design is a significant advancement toward a functional microphone for fully implanted cochlear implants.
• Promising bench and cadaveric performance warrants further research into complete device biocompatibility, fixation, and long-term implantation studies.