A fuel cell that runs on the same sugar that powers the cells in our bodies could help drive neural prosthetics – helping paralyzed patients use their thoughts to move their limbs. MIT News reports.
Okay, actually, this sweet new energy source isn’t actually that new. Scientists in the 70s powered a pacemaker on a glucose fuel cell, but those were abandoned in favor of lithium-ion batteries that provided more power. Plus, those used enzymes, which eventually stopped functioning efficiently.
So a team led by MIT’s Rahul Sarpeshkar added a new twist. Their fuel cell creates a small electric current by stripping electrons from glucose molecules. It uses a platinum catalyst to do this, mimicking the activity of cellular enzymes that break down glucose to generate ATP, or units of energy. (Platinum has a proven record of long-term biocompatibility within the body.)
The way we metabolize glucose is pretty complex, involving a cycle of oxidizing enzymatic reactions that knock electrons off the molecule one by one. At the end of the process, the molecule has been ravaged, all 24 electrons have been picked off and salvaged. Fuel cells work by the same principle, but only remove 2 electrons.
“Ours is like a baby oxidation,” Sarpeshkar says.
So far, the fuel cell can generate up to hundreds of microwatts – enough to power an ultra-low-power and clinically useful neural implant.
In theory, the glucose fuel cell could get all the sugar it needs from the cerebrospinal fluid that bathes the brain and protects neural tissue from banging around. The rich amount of glucose in the fluid doesn’t really get used by the body, and since there are few cells in the fluid, an implant there is unlikely to provoke an immune response.
The fuel sits in a chip made of silicon – like those used to make semiconductor electronic chips – which allows the fuel cell to be integrated with other circuits that would be needed for a brain implant.
Sarpeshkar’s group has worked on all aspects of implantable brain-machine interfaces and neural prosthetics. One such device records electrical activity from hundreds of neurons in the brain area responsible for controlling movement. Those data are converted into a digital signal for brain-implanted microchips to analyze – determining which patterns of brain activity produce movement.
They’ve just begun working on bringing their ultra-low-power electronics to market, but glucose-powered bioelectronics are still years away.
The technology is described in PLoS ONE this week.
Image from Rapoport et al., PLoS ONE 2012