One day, the sweat you produce during exercise could power small electronic devices.
Researchers at the University of California San Diego have designed what they’re calling a biobattery in the form of a temporary tattoo.
The battery works by “detecting and responding to lactate,” which is found in sweat. When your body needs more energy because of physical exertion, a process called glycolysis occurs. Glycolysis basically turns sugars into usable energy for the body. A byproduct of this process is lactate.
The biobattery tattoo contains an enzyme that “strips electrons from lactate,” which creates an electrical current. That enzyme was imprinted on tattoo paper to finish the device. While the tattoo is about a centimeter square, the electrodes are only two or three millimeters in size.
"These represent the first examples of epidermal electrochemical biosensing and biofuel cells that could potentially be used for a wide range of future applications," said researcher Joseph Wang in a statement.
Researchers put the tattoos, which cost “a few cents” to make, on the upper arms of several volunteers who exercised on stationary bicycles for half an hour.
More exercise did not mean more power generation, however.
The less fit volunteers actually produced more energy than their fit counterparts. Researchers said this was likely due to the earlier onset of glycolysis and production of lactate in the less fit volunteers.
So far, the current generated has been weak, a mere 70 microwatts per square centimeter of skin. That would not be enough to power a watch. However, researcher Wenzhao Jia said two or three of the tattoos would probably provide enough power.
"The current produced is not that high, but we are working on enhancing it so that eventually we could power some small electronic devices," said Jia.
Another possibility for the biobatteries would be to put them in clothing which would provide a large surface area, Jia said.
If the researchers are able to make the biobatteries viable, they could offer advantages over conventional batteries in that they charge more quickly, use a renewable source of energy and would not explode or contain toxic chemicals.
The team described the biobatteries at the 248th National Meeting & Exposition of the American Chemical Society in San Francisco.
Here's a video about the device: