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, researchers said.
Existing versions of the device, however, require that a disk-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.
It would run for about eight hours on each charge.
The researchers described their chip in a paper they will present this week at the International Solid-State Circuits Conference.
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They 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," said Anantha Chandrakasan, the Joseph F and Nancy P Keithley Professor of Electrical Engineering and corresponding author on the new paper.
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.
A middle-ear implant consists of a tiny sensor that detects the ossicles' vibrations and an actuator that helps drive the stapes accordingly.
The new device would use the same type of sensor, but the signal it generates would travel to a microchip implanted in the ear, which would convert it to an electrical signal and pass it on to an electrode in the cochlea.