Assistive devices such as hearing aids have become smaller and smaller in recent years, but they are still limited by the size of their batteries. Although they are no longer generally so large that they have to be worn around your neck, hearing aids can be clunky and cumbersome. In searching for a way to provide more manageable power, researchers have often wondered if there might be a way to harness the power within the human body. The cochlea for instance, is actually a sort of mini-battery with differing levels of potassium and sodium ions on opposing sides of a membrane, but until now no one really imagined that harnessing that power without disrupting the natural processes of the inner ear was possible.
Enter a team of researchers in Boston whose combined expertise may make human-powered implantable hearing aids a reality. Konstantina Stankovic is an otologic surgeon at Massachusetts Eye and Ear Infirmary with a background in physics and technology. She and graduate student Andrew Lysaght thought there might be a way to harness the voltage created by the cochlea to power a useful electronic device. In order to do that though, they needed a device that could operate on a very low and fluctuating voltage, because the battery in our ears is nowhere near as powerful as a regular AAA. Luckily, the engineers in MIT’s Microsystems Technology Laboratories (MTL) are developing devices that can do just that.
Anantha Chandrakasan heads MIT’s Department of Electrical Engineering and Computer Science. He worked with graduate students Patrick Mercier and Saurav Bandyopadhyay to develop a tiny low-powered radio transmitter that could operate on a mere one nanowatt (or one billionth of a watt) of power. When Stankovic and Lysaght implanted electrodes attached to this device into the ears of guinea pigs it was able to send them regular measurements of the potential within the ears without disrupting the animals’ hearing. The ability to implant a device that would measure this potential could be a powerful diagnostic tool on its own, but the technology could develop into more. It will certainly be a while before anyone tries to implant an ear-powered hearing aid, but thanks to some creative engineers we are a big step closer.