Implants like pacemakers can run for decades, so they need a steady supply of power, and cables can’t just be run through a patient’s skin. A battery might be the obvious solution, but replacing the battery requires surgery. Even with new advances in out-of-body wireless charging, batteries add too much bulk for devices that need to be as small and light as possible.
Ideally, implants would be fitted with devices that would generate their own electricity, and what better than the abundance of energy our own cells use? Glucose fuel cells, which convert the chemical energy of blood sugar into electricity, have been in development for decades, but they still have some problems to solve. And now, a new device developed by researchers at MIT and the Technical University of Munich may have some answers.
The structure of the new fuel cell is basically the same as the existing fuel cell, consisting of an anode, an electrolyte and a cathode. The anode reacts with glucose in the body fluid to produce gluconic acid, which releases two protons and two electrons. Electrolytes carry away protons, where they mix with air and become harmless water molecules. Meanwhile, the electrons are collected into an electrical circuit, where they can be used to power implanted devices.
Most of the time, the electrolytes in glucose fuel cells are made of polymers, but for their device, the researchers used a new material — ceria, a strong, stable ceramic that conducts well protons, and has been used for the same work in hydrogen fuel cells. The electrodes are made of platinum, which reacts strongly with glucose.
The final cell was small — about 300 microns wide and only 400 nanometers thick. To test them, the researchers fabricated 150 cells on silicon wafers, flowed a glucose solution over their tops, and measured their electrical output.
The fuel cells produced a peak voltage of about 80 millivolts, which equates to about 43 microwatts per square centimeter. This, the team says, is the highest power density of any glucose fuel cell made to date and is sufficient to power an implantable device.
In addition to high output, the ceramic material helps it last longer and can withstand high temperatures prior to implantationdisinfect. These fuel cells could be made into thin-film coatings and wrapped around implants to power them, the researchers said.
The study was published inAdvanced Materials” magazine.