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Your ear is a battery...can power tiny devices!

Posted: 09 Nov 2012     Print Version  Bookmark and Share

Keywords:ear  battery  implantable electronic  electrical voltage 

Deep inside your ear is a battery; and scientists, for the first time, have harnessed this "natural battery" to power implantable electronic devices without impairing hearing, and even used to to deliver medicines and therapies.

The ear converts a mechanical force—the vibration of the eardrum—into an electrochemical signal that can be processed by the brain; the biological battery is the source of that signal's current. Located in the part of the ear called the cochlea, the battery chamber is divided by a membrane, some of whose cells are specialised to pump ions. An imbalance of potassium and sodium ions on opposite sides of the membrane, together with the particular arrangement of the pumps, creates an electrical voltage.

In experiments, researchers from MIT, the Massachusetts Eye and Ear Infirmary (MEEI) and the Harvard-MIT Division of Health Sciences and Technology (HST), implanted a low-power chip in guinea pigs' ears. After the implantation, the guinea pigs were said to respond normally to hearing tests, and the devices were able to wirelessly transmit data about the chemical conditions of the ear to an external receiver.

However, researchers feel device powered by the biological battery can harvest only a small fraction of its power.

The chip was equipped with an ultra low power radio transmitter and power conversion circuitry. To reduce its power consumption, the control circuit had to be drastically simplified, but like the radio, it still required a higher voltage than the biological battery could provide. Once the control circuit was up and running, it could drive itself; the problem was getting it up and running.

The researchers solve that problem with a one-time burst of radio waves. "In the very beginning, we need to kick-start it," said Anantha Chandrakasan, who heads MIT's Department of Electrical Engineering and Computer Science. "Once we do that, we can be self-sustaining. The control runs off the output."

Cliff Megerian, chairman of the otolaryngology department at Case Western Reserve University, said, "The fact that you can generate the power for a low voltage from the cochlea itself raises the possibility of using that as a power source to drive a cochlear implant,"

"I'm not ready to say that the present iteration of this technology is ready," Megerian cautions. But he adds that, "If we could tap into the natural power source of the cochlea, it could potentially be a driver behind the amplification technology of the future."

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