Cochlear implants that are entirely implanted could soon be on the way thanks to researchers in the US.

A team from MIT has created a low cost, low power chip that uses the natural microphone of the middle ear rather than a skull-mounted sensor to pick up sound. The system can be wirelessly recharged in minutes via a smartphone and has a battery life of around eight hours. "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," explained researcher Anantha Chandrakasan. "Or you could imagine a smart pillow, so you charge overnight, and the next day, it just functions." Middle ear implants work by relaying vibrations from the eardrum to the cochlea, effectively filling in for a defective bone inside the ear. The MIT chip uses the same type of sensor, but the signal it generates travels to a microchip implanted in the ear, which converts it to an electrical signal and then passes it on to an electrode in the cochlea. The researchers believe the system could be completely implanted not just because it would be much smaller than all the parts of a conventional cochlear implant, but also because it would have considerably lower power requirements. Although installation would require complex surgery, the scientists believe the procedure would get quicker as specialists got more familiar with it. So far, the team has tested it on four patients who already had cochlear implants and found that it had no effect on their ability to hear.