The fuel cell could be used to power brain implants for treating epilepsy, Parkinson's diseases and paralysis. Currently, devices implanted in the body are typically powered by lithium-ion batteries, but they have a limited lifetime and need to be replaced. Opening up the body to replace a battery is not something doctor like to do, but doing it in the brain is even less desirable.
The researchers, led by Rahul Sarpeshkar, an associate professor of electrical engineering and computer science, built the fuel cell using a platinum catalyst at one end and a layer of carbon nanotubes at the other. It rests on a silicon chip, allowing it to be connected to electronics that would be used in brain implants.
As glucose passes over the platinum, electrons and hydrogen ions are stripped off as it is oxidized. That's what makes the current. At the other end of the cell, oxygen mixes with the hydrogen to make water when it hits the layer of single-walled carbon nanotubes. The cell produces up to 180 microwatts, enough to power a brain implant that might send signals to bypass damaged region, or stimulate part of the brain (a treatment used in disorders such as Parkinson's).
Glucose fuel cells are an old idea, dating to the 1970s, and a similar kind of fuel cell was proposed by French scientists in 2010 to power pacemakers. That cell was a mix of graphite and enzymes that separated the electrons from the glucose. The problem is that the enzyme-powered cells weren't able to run as long with as much output as lithium-ion batteries.
MIT's cell will keep working as long as there is glucose and water. The glucose to power it would come from the cerebrospinal fluid that surrounds the brain. Much of the glucose there isn't used by the body, and the fuel cell only uses a small fraction of that, so it shouldn't affect brain function.
The cell hasn't yet been tested in an actual brain, just a solution that mimics the fluid around it. It is still a promising step towards implants, even though it will be years before anyone is walking around with one in their heads.
The team published their work in the June 12 edition of the journal PLoS ONE.