Cochlear implants, which electrically stimulate the auditory nerve, grant some hearing to those who might otherwise be deaf. One drawback has been that the devices require that a transmitter be affixed externally 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.

Researchers at MIT’s Microsystems Technology Laboratory, Cambridge, MA, together with physicians from Harvard Medical School and the Massachusetts Eye and Ear Infirmary, say that they have developed a new, low-power signal-processing chip that could lead to a cochlear implant that requires no external hardware. The implant would be wirelessly recharged and would run for about eight hours on each charge.

The researchers explain that their prototype charger plugs into an ordinary cell phone and can recharge the signal-processing chip in about two minutes. This way, the user does not have to be plugged in.

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 at MIT are developing a new waveform, the basic electrical signal modulated to encode acoustic information, that is power-efficient to generate but still stimulates the auditory nerve in the appropriate way. They were able to tailor it for cochlear implants and found a low-power way to implement it in hardware. In demonstrations, the researchers proved that the chip and sensor are able to pick up and process speech played into a the middle ear of a human cadaver.

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