The “battery chamber” is located in the cochlea. It is internally divided by a membrane, some of the cells of which are designed to pump ions. The arrangement of those specialized cells, combined with an imbalance of potassium and sodium ions on opposite sides of the membrane, are what creates the electrical voltage.
A team of scientists from MIT, the Massachusetts Eye and Ear Infirmary, and the Harvard-MIT Division of Health Sciences and Technology have recently succeeded in running an ultra-low-power radio-transmitting chip using power from these battery chambers – in guinea pigs’ ears."
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