A natural battery in the ear could help power medical electronics such as hearing aids and diagnostics. Researchers at MIT have found a way to harvest this energy by implanting electrodes in the biological batteries in guinea pigs.
The ear converts the vibration of the eardrum into an electrochemical signal that can be processed by the brain. The natural battery in the ear is the source of the signal’s current. Scientists have known for 60 years that this natural battery exists, but the energy has not been used to power electronics before because if too much energy is harvested, hearing can be impaired. Researchers were able to harvest the energy without disrupting the hearing of the guinea pigs in the study. Eventually, the technique could be used to power devices that monitor biological activity and responses to therapy in humans, or deliver therapy themselves.
The researchers in the study attached low-power electronic devices, developed by MIT’s Microsystems Technology Laboratories, to the electrodes. The devices transmitted data about the chemical conditions of the ear to an external receiver. The chip was equipped with an ultralow-power radio transmitter. The radio required more energy than the biological battery could provide, so the research team used a power-conversion circuitry to gradually build up charge in a capacitor. The control circuit also required higher voltage than the biological battery would provide, so the team used a one-time burst of radio waves to kick-start it.Camilla Andersson