Abstract: Cochlear implants are devices that can restore hearing in people with sensorineural deafness. Despite their name, cochlear implants rely on an external unit that contains the microphone, battery, and sound processor. Internalizing this unit would greatly benefit users by enabling 24/7 hearing, regardless of activity. The most challenging part of developing a fully implantable cochlear implant is the microphone. This talk presents the design, fabrication, and testing of a microphone implanted in the middle ear that senses the motion of the ossicular chain.
The implantable microphone is a piezoelectric displacement sensor that contacts the umbo, the point where the malleus attaches to the tympanic membrane. The bimorphic microphone sensors are fabricated from two layers of the piezoelectric film polyvinylidene fluoride (PVDF), and are made completely from biocompatible materials. The differential charge output of the bimorph design provides low noise and effective EMI rejection.
We tested the microphones both on the bench and in fresh human cadavers. The devices show a flat frequency response within 15 dB SPL from about 100 Hz to 10 kHz, high sensitivity, good linearity, and equivalent input noise comparable to commercial hearing aid microphones.
This prototype demonstrates the feasibility of an implanted microphone and represents an important step toward developing a fully implantable cochlear implant.
Bio: Emma Wawrzynek is a fourth-year PhD student at MIT in the Electrical Engineering and Computer Science department under the advisorship of Professor Jeffrey Lang and Professor Heidi Nakajima. Her research focuses on cochlear implants, a medical device that restores hearing to people with sensorineural deafness. She works on the design, fabrication, and testing of a piezoelectric implantable microphone for cochlear implants. Prior to MIT, Emma received a B.S. in Bioengineering at University of California, Berkeley, where she conducted research on printed, flexible electronics with Professor Ana Claudia Arias.