A very small fuel cell capable of running on glucose in our blood
Engineers from the Massachusetts Institute of Technology (MIT) and the Technical University of Munich (Technische Universität München) have developed a very thin fuel cell that may be able to power medical implantable devices in the future, working from glucose in the patient's blood.
The thickness of the fuel cell is only 400 nanometers (about one hundredth of the diameter of a human hair), it is elastic and able to withstand temperatures up to 600℃. The latter is necessary so that it can be subjected to high-temperature sterilization before implantation into the body.
The developers of the element believe that in the future implants can be wrapped with ultrathin films using glucose, which is abundant in the body, to generate electricity. Today, batteries are used in implants. But the battery can make up to 90% of the volume of the device. The newly developed fuel cell will probably reduce the implants by several times.
The idea to create something like this first came to Jennifer Rupp, an associate professor of solid-state electrolyte chemistry at the Technical University of Munich and a visiting professor at MIT, when in 2016, while monitoring the course of pregnancy, she went to take a routine sugar test. She was bored in the doctor's office and entertained herself by thinking about what could be done with sugar and electrochemistry. And suddenly I thought that it would be nice to have a solid-state device running on glucose. Later, she shared the idea with her doctoral student from MIT, Philip Simons, and together, over coffee, they made the first sketches on napkins.
This is not the world's first glucose fuel cell. The first appeared back in the 1960s, were based on soft polymers and could not compete with lithium-iodide batteries, which became the standard source of electric current for medical implants, primarily for pacemakers.
However, lithium-iodide batteries have a significant lower size limitation, since their design requires a volume for storing reagents. Therefore, in recent years, scientists have been looking towards glucose fuel cells as potentially more compact energy sources for medical implants: glucose does not need to be stored in a fuel cell — there is already plenty of it in the body.
The developers used cerium as an electrolyte in the new fuel cell: it is biocompatible, mechanically durable and is widely used in hydrogen fuel cells. The anode and cathode were made of platinum. Having built 150 separate glucose fuel cells on a chip, each about 400 nanometers thick and about 300 micrometers wide, the inventors applied them to silicon wafers, and then measured the current generated by each cell when passing a glucose solution. It turned out that many of the resulting cells produce a voltage of about 80 millivolts. The developers claim that their invention currently produces the largest power output among all existing glucose fuel cells — 43 microwatts per square centimeter.
Of course, many more different tests will be required, but, apparently, it is quite possible to use the new element to power implantable devices.
Article by Simons et al. A Ceramic-Electrolyte Glucose Fuel Cell for Implantable Electronics is published in the journal Advanced Materials.
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