The Tiny UmboMic Piezo Microphone Brings Us a Step Closer to Fully-Internal Cochlear Implants
The size of a grain of rice, the UmboMic turns tiny vibrations from the middle ear into electricity thanks to a PVDF sandwich.
Researchers from the Massachusetts Institute of Technology, Harvard Medical School, and Columbia University have developed a prototype for an implantable microphone, the UmboMic, moving closer to the possibility of a fully-internal cochlear hearing implant.
"Our goal is that a surgeon implants this device at the same time as the cochlear implant and internalized processor," co-lead author Emma Wawrzynek, electrical engineer and computer science (EECS) graduate, explains of the team's work, "which means optimizing the surgery while working around the internal structures of the ear without disrupting any of the processes that go on in there."
The UmboMic represents one step towards an improved design for cochlear implants, designed to offer deaf and hard of hearing people an electronic sense of sound — but which, at present, rely on both internal implants and an external unit housing a microphone. Doing away with the external part of the system would make it easier for cochlear implant users to swim, exercise, and sleep more comfortably without losing their sense of hearing for the duration.
The team's microphone is designed to be implanted within the user's ear, pushing against the umbo — a part of the middle ear that vibrates in response to sound waves. The UmboMic is made from sandwich of polyvinylidene difluoride (PVDF), a piezoelectric material compatible with the human body, which deforms with these vibrations and generates electricity for the rest of the system to turn back into sound. The finished device is roughly the size of a grain of rice, making it easily implantable.
Testing shows the design works well, with the opposing layers of PVDF generating opposing charges that can be used to filter out noise and a custom low-noise low-power amplifier working well. Widespread use in human patients, though, could be a little further out yet: "One thing we saw that was really interesting is that the frequency response of the sensor is influenced by the anatomy of the ear we are experimenting on," Wawrzynek explains, "because the umbo moves slightly differently in different people's ears" — something the team would have to account for in broad deployments.
The team's work has been published under closed-access terms in the Journal of Micromechanics and Microengineering; an open-access preprint is available on Cornell's arXiv server. If you have your own ideas for using technology to improve accessibility and inclusion, why not submit them to our Build2gether 2.0 Inclusive Innovation Challenge — now open through August 15th and with over $100,000 in prizes available.