Chip enables wireless charging of cochlear implants12 Feb 2014 | Larry Hardesty
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Researchers at MIT's Microsystems Technology Laboratory (MTL), together with physicians from Harvard Medical School and the Massachusetts Eye and Ear Infirmary (MEEI), have created a low-power signal-processing chip that could eliminate the need for external hardware in cochlear implants. The implant, which uses the natural microphone of the middle ear rather than a sensor, is designed for wireless recharging and could run for about eight hours on each charge.
Cochlear implants—medical devices that electrically stimulate the auditory nerve—have granted at least limited hearing to hundreds of thousands of people worldwide who otherwise would be totally deaf. Existing versions of the device, however, require that a disc-shaped transmitter about an inch in diameter be affixed to the skull, with a wire snaking down to a joint microphone and power source that looks like an oversized hearing aid around the patient's ear.
The researchers describe their chip in a paper they're presenting at the International Solid-State Circuits Conference. The researchers will also exhibit a prototype charger that plugs into an ordinary cell phone and can recharge the signal-processing chip in roughly two minutes.
"The idea with this design is that you could use a phone, with an adaptor, to charge the cochlear implant, so you don't have to be plugged in," says Anantha Chandrakasan, the Joseph F. and Nancy P. Keithley Professor of Electrical Engineering and corresponding author on the new paper. "Or you could imagine a smart pillow, so you charge overnight, and the next day, it just functions."
Existing cochlear implants use an external microphone to gather sound, but the new implant would instead use the natural microphone of the middle ear, which is almost always intact in cochlear-implant patients.
The researchers' design exploits the mechanism of a different type of medical device, known as a middle-ear implant. Delicate bones in the middle ear, known as ossicles, convey the vibrations of the eardrum to the cochlea, the small, spiral chamber in the inner ear that converts acoustic signals to electrical. In patients with middle-ear implants, the cochlea is functional, but one of the ossicles—the stapes—doesn't vibrate with enough force to stimulate the auditory nerve. A middle-ear implant consists of a tiny sensor that detects the ossicles' vibrations and an actuator that helps drive the stapes accordingly.
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