Lactate

His thick fingers crackle across a large packet containing empty purple sachets labeled alcohol swabs, used syringes and a plastic sheath that a few minutes ago contained lactate solution.

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.