Good news!
"... Now researchers at Columbia Engineering and their colleagues have developed a tiny microphone totally implantable within the head, an advance recently chosen as one of the Journal of Micromechanics and Engineering's highlights of 2024. The work is in collaboration with MIT and Harvard Medical.
Around the world, more than a million people have received cochlear implants, according to the National Institutes of Health. ...
Now, by making use of the bones inside the head that allow people to hear, researchers ... have developed the UmboMic, a prototype microphone that they say is a promising step toward a completely implantable cochlear implant. ...
The UmboMic focuses on the motion of the umbo, the tip of the hammer-shaped bone connected to the eardrum. The umbo mostly vibrates only up and down, making it much easier to analyze than the more complex motions of other ear bones.
The key sensor in the UmboMic is an ironing-board-shaped sliver roughly 3 millimeters long, about twice the average length of a flea, and 200 microns thick, about twice the average width of a human hair. This sensor is made of a highly flexible plastic called polyvinylidene difluoride (PVDF), which is piezoelectric — it can convert mechanical energy into electricity.
"We started talking about how PVDF could be incorporated into a totally implantable cochlear implant back in 2009," Kymissis says.
The sensor's triangular tip rests against the umbo, detecting motions only a few nanometers large. In tests of the UmboMic with human temporal bones, which house the internal parts of the ear, the sensor could convert sounds into electrical signals, performing as well as a conventional hearing aid's microphone. ..."
From the 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–7 kHz, good linearity, and a flat frequency response to within 10 dB from about 100 Hz–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."
The UmboMic: a PVDF cantilever microphone (no public access)
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