A new implantable fuel cell that harvests the electrical power from the brain promises to usher in a new generation of bionic implants. Designed by MIT researchers, it uses glucose within the cerebrospinal fluid surrounding the brain to generate several hundred microwatts of power without causing any detrimental effects to the body. The technology may one day provide a whole new level of reliability and self-efficiency for all sorts of implantable brain-machine interfaces that would otherwise have to rely on external power sources.
So far, two computer chip-shaped fuel cells have been tested in a saline solution simulating the cerebrospinal fluid. The prototypes come in one square millimeter and two square millimeter varieties. They work by oxidizing glucose present in the cerebrospinal fluid at the surface of an activated platinum anode and then converting the oxygen into water at the cathode end of the cell, where single-walled carbon nanotubes are embedded. Electrons stripped from the glucose in the process are used to generate electricity.
One of the advantages of a fuel cell over a battery is that it can operate indefinitely provided an uninterrupted supply of fuel and oxygen. The new tiny fuel cell could potentially operate continuously for decades. Current brain-machine interfaces, on the other hand, are either powered wirelessly, through electrical induction, or by disposable batteries that need to be surgically replaced after several years.
Although not yet tested in an actual brain, a lot has been done to gauge the fuel cell’s safety. It turned out that it consumes glucose at 2.8 to 28 percent of the rate at which the simple sugar is replenished by the organism, so no adverse effects should be caused. Similarly, the calculated levels of oxygen consumption have been shown to be low enough not to shift the oxygen balance in the brain. Since it’s said to be the first-ever attempt at using the cerebrospinal fluid as the fuel medium for an implantable fuel cell, the scientists are exploring a completely new field ... one that has so far proved very promising.
Rahul Sarpeshkar, an associate professor of electrical engineering and computer science at MIT and leader of the team behind the project, is already preparing for tests on animals, and then on humans. Should the results confirm that the full cells cause no detrimental effect to the organism, it will be possible to manufacture them together with integrated circuits on a single silicon wafer. Implants powered by this technology may one day help tackle blindness, paralysis and various deep brain disorders.
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