Ultrathin Fuel Cells Could Use Your Body’s Sugar to Power Implants

Your own body could be a power source for future gadgets. 

MIT scientists have developed a glucose-powered fuel cell that could fuel miniature implants and sensors. The device measures about 1/100 the diameter of a human hair and generates about 43 microwatts per square centimeter of electricity. The fuel cells could be useful in medicine and the small but growing number of people who implant electronic gadgets in their bodies for convenience. 

"Glucose fuel cells can become useful to power implantable devices using a fuel readily available in the body," Philipp Simons, who developed the design as part of his Ph.D. thesis, told Lifewire in an email interview. "For example, we envision using our glucose fuel cell to power highly miniaturized sensors which measure body functions. Think glucose monitoring for diabetes patients, monitoring cardiac conditions, or tracking biomarkers that identify the evolution of a tumor."

Tiny but Mighty

The biggest challenge in designing the new fuel cell was coming up with a design that was small enough, Simons said. He added that implantable devices need to be as small as possible to minimize their impact on patients. 

"Currently, batteries are very limited in how small they can become: if you make a battery smaller, it reduces how much energy it can provide," Simons said. "We have shown that with a device that is 100 times thinner than a human hair, we can provide energy that would suffice to power miniature sensors."

Simons and his collaborators had to make the new device able to generate electricity and tough enough to withstand temperatures up to 600 degrees Celsius. If used in a medical implant, the fuel cell would have to go through a high-temperature sterilization process. 

To find a material that could withstand the high heat, the researchers turned to ceramic, which retains its electrochemical properties even at high temperatures. The researchers envision the new design could be made into ultrathin films or coatings and wrapped around implants to passively power electronics, using the body's abundant glucose supply.

The idea for the new fuel cell came in 2016 when Jennifer L.M. Rupp, Simons' thesis supervisor and an MIT professor, who specializes in ceramics and electrochemical devices, went for a glucose test during her pregnancy.

"In the doctor's office, I was a very bored electrochemist, thinking what you could do with sugar and electrochemistry," Rupp said in a news release. "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."

Glucose fuel cells were first introduced in the 1960s, but the early models were based on soft polymers. These early fuel sources were replaced by lithium-iodide batteries. 

"To date, batteries are typically used to power implantable devices such as pacemakers," Simons said. "However, these batteries will eventually run out of energy which means a pacemaker needs to be regularly replaced. This is actually a huge source of complications."

The Future May Be Small and Implantable

In the search for a fuel cell solution that could last indefinitely inside the body, the team sandwiched an electrolyte with an anode and cathode made of platinum, a stable material that readily reacts with glucose.

The type of materials in the new glucose fuel cell allows flexibility in terms of where it can be implanted in the body. "For example, it can withstand the corrosive environment of the digestive system, which could enable new sensors monitoring chronic diseases such as irritable bowel syndrome," Simons said. 

The researchers put 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.

Many cells produced a peak voltage of about 80 millivolts, according to results published in a recent paper in the journal Advanced Materials. The researchers claim this is the highest power density of any glucose fuel cell design.

The MIT team has "opened a new route to miniature power sources for implanted sensors and maybe other functions," Truls Norby, a professor of chemistry at the University of Oslo in Norway, who did not contribute to the work, said in a news release. "The ceramics used are non-toxic, cheap, and not [the] 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."

Simons said that the new fuel cells could enable entirely new classes of devices in the future. "Given how small our fuel cell is, one can imagine implantable devices that are only a few micrometers big," he added. "What if we could now address individual cells with implantable devices?"