Researchers have managed to run a tiny medical gadget meant to be used inside the human body by utilising a natural battery that's located deep within the inner ear
Deep in the inner ear of mammals is a natural battery - a chamber filled with ions that produces an electrical potential to drive neural signals. In the journal Nature Biotechnology, a team of researchers from MIT, the Massachusetts Eye and Ear Infirmary (MEEI) and the Harvard-MIT Division of Health Sciences and Technology (HST) demonstrate for the first time that this battery could power implantable electronic devices without impairing hearing.
The devices could monitor biological activity in the ears of people with hearing or balance impairments, or responses to therapies. Eventually, they might even deliver therapies themselves.
In experiments, Konstantina Stankovic, an otologic surgeon and student Andrew Lysaght implanted electrodes in the biological batteries in guinea pig's ears. Attached to the electrodes were low-power electronic devices. After the implantation, the guinea pigs responded normally to hearing tests, and the devices were able to wirelessly transmit data about the chemical conditions of the ear to an external receiver.
"In the past, people have thought that the space where the high potential is located is in accessible for implantable devices, because potentially it's very dangerous if you encroach on it," Stankovic says. "We have known for 60 years that this battery exists and that it's really important for normal hearing, but nobody has attempted to use this battery to power useful electronics."
The ear converts a mechanical force - the vibration of the ear drum - 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.
Although the voltage is the highest in the bidy (outside of individual cells, at least), it's still very low. Moreover, in order not to disrupt hearing, a device powered by the biological battery can harvest only a small fraction of its power. Anantha Chandrakasan, who heads MIT's Department of Electrical Engineering and Computer Science; his group - equipped their chip with an ultralow-power radio transmitter: After all, an implantable medical monitor wouldn't be much use if there were no way to retrieve its measurements.
But while the radio is much more efficient than those found in cellphones, it still couldn't run directly on the biological battery. 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. That issue was sloved with a one-time burst of radio waves." In the very beginning, we need to kick-start it," Chandrakasan says. "Once we do that, we can be self-sustaining. The controls runs off the output."
Deep in the inner ear of mammals is a natural battery - a chamber filled with ions that produces an electrical potential to drive neural signals. In the journal Nature Biotechnology, a team of researchers from MIT, the Massachusetts Eye and Ear Infirmary (MEEI) and the Harvard-MIT Division of Health Sciences and Technology (HST) demonstrate for the first time that this battery could power implantable electronic devices without impairing hearing.
In experiments, Konstantina Stankovic, an otologic surgeon and student Andrew Lysaght implanted electrodes in the biological batteries in guinea pig's ears. Attached to the electrodes were low-power electronic devices. After the implantation, the guinea pigs responded normally to hearing tests, and the devices were able to wirelessly transmit data about the chemical conditions of the ear to an external receiver.
"In the past, people have thought that the space where the high potential is located is in accessible for implantable devices, because potentially it's very dangerous if you encroach on it," Stankovic says. "We have known for 60 years that this battery exists and that it's really important for normal hearing, but nobody has attempted to use this battery to power useful electronics."
The ear converts a mechanical force - the vibration of the ear drum - 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.
Although the voltage is the highest in the bidy (outside of individual cells, at least), it's still very low. Moreover, in order not to disrupt hearing, a device powered by the biological battery can harvest only a small fraction of its power. Anantha Chandrakasan, who heads MIT's Department of Electrical Engineering and Computer Science; his group - equipped their chip with an ultralow-power radio transmitter: After all, an implantable medical monitor wouldn't be much use if there were no way to retrieve its measurements.
But while the radio is much more efficient than those found in cellphones, it still couldn't run directly on the biological battery. 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. That issue was sloved with a one-time burst of radio waves." In the very beginning, we need to kick-start it," Chandrakasan says. "Once we do that, we can be self-sustaining. The controls runs off the output."
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