Custom experimental setup used to characterize 30 glucose fuel cells in rapid sequence.
The team looked to improve on existing materials and designs by modifying the electrolyte layer, which is often made from polymers. But polymer properties, along with their ability to conduct protons, easily degrade at high temperatures, are difficult to retain when scaled down to the dimension of nanometers, and are hard to sterilize. The researchers wondered if a ceramic — a heat-resistant material which can naturally conduct protons — could be made into an electrolyte for glucose fuel cells. “When you think of ceramics for such a glucose fuel cell, they have the advantage of long-term stability, small scalability, and silicon chip integration,” Rupp notes. “They’re hard and robust.”
The researchers designed a glucose fuel cell with an electrolyte made from ceria, a ceramic material that possesses high ion conductivity, is mechanically robust, and as such, is widely used as an electrolyte in hydrogen fuel cells. It has also been shown to be biocompatible. “Ceria is actively studied in the cancer research community,” Simons notes. “It’s also similar to zirconia, which is used in tooth implants, and is biocompatible and safe.”
The team sandwiched the electrolyte with an anode and cathode made of platinum, a stable material that readily reacts with glucose. They fabricated 150 individual glucose fuel cells on a chip, each about 400 nanometers thin, and about 300 micrometers wide (about the width of 30 human hairs). They patterned the cells onto silicon wafers, showing that the devices can be paired with a common semiconductor material. They then measured the current produced by each cell as they flowed a solution of glucose over each wafer in a custom-fabricated test station. They found many cells produced a peak voltage of about 80 millivolts. Given the tiny size of each cell, this output is the highest power density of any existing glucose fuel cell design. “Excitingly, we are able to draw power and current that’s sufficient to power implantable devices,” Simons says. “It is the first time that proton conduction in electroceramic materials can be used for glucose-to-power conversion, defining a new type of electrochemstry,” Rupp says. “It extends the material use-cases from hydrogen fuel cells to new, exciting glucose-conversion modes.”
The researchers “have opened a new route to miniature power sources for implanted sensors and maybe other functions,” says Truls Norby, a professor of chemistry at the University of Oslo in Norway, who did not contribute to the work. “The ceramics used are nontoxic, cheap, and not least inert both to the conditions in the body and to conditions of sterilization prior to implantation. The concept and demonstration so far are promising indeed.”
Source: Massachusetts Institute of Technology
Source: Healthcare in Europe
