If our body’s cells are powered by the glucose that we get from the food that we eay, why not sugar-powered fuel cells for medical implants and wearables? That’s the question that’s been asked and mostly answered by researchers at MIT and the University of Munich. They’ve joined forces to create a unique fuel cell that generates electricity from glucose. While glucose fuel cells have been around for decades, the size here is a novel development; with a thickness of just 400 nanometers, the new device is nearly 100 times thinner than a human hair. Researchers envision that the power source could be made into coatings or into thin films that wrap around implants while providing them with power.
Compared to previous glucose cells, the new device has a higher power density: around 43 microwatts for every square centimeter of electricity. And perhaps best of all, the body’s own glucose supply can fuel this power source. MIT researcher Philipp Simons says, “Glucose is everywhere in the body, and the idea is to harvest this readily available energy and use it to power implantable devices.” Fellow researcher Jennifer L.M. Rupp adds, “Instead of using a battery, which can take up 90 percent of an implant’s volume, you could make a device with a thin film, and you’d have a power source with no volumetric footprint.”
Most glucose fuel cells have three layers: a bottom cathode, a middle electrolyte, and a top anode. The middle layer is traditionally made of polymers that don’t hold up well under extreme heat, making them incompatible with implantable devices that must go through a high-heat sterilization process. So the research team turned to ceramics. The new ceramic fuel cell can withstand temperatures as high as 600 degrees Celsius (1,112 degrees Fahrenheit). Ceramic also helps the device to maintain its electrochemical properties at a miniature scale. And the type of ceramic material that the device uses — ceria — has been proven to be biocompatible. Simons says, “[Ceria is] similar to zirconia, which is used in tooth implants, and is biocompatible and safe.”
The idea for the ceramic power source came to Rupp on a routine visit with her doctor to get a glucose test during her pregnancy. She recalls, “In the doctor’s office, I was a very bored electrochemist, thinking what you could do with sugar and electrochemistry. Then I realized, it would be good to have a glucose-powered solid-state device. And Philipp and I met over coffee and wrote out on a napkin the first drawings.”