Though some may find it disgusting, sweat is a useful material as performs a necessary for regulating body temperature. It also contains compounds that can provide information about a person thanks to some new research, as reported by the American Chemical Society. The researchers went farther than just creating a sensor though by building a biofuel cell powered by sweat.
When people exercise, the body needs energy to fuel its muscles, and for particularly strenuous activities it activates glycolysis. This process produces the needed energy as well as the compound lactate, and by measuring the amount of lactate, a doctor can determine the person's fitness. Traditionally making these measurements required taking blood samples, but the researchers discovered a way to actually measure it in sweat using electrochemistry. The sensor, which has been built into a temporary tattoo, actually pulls electrons off of the lactate molecule, creating a weak current, and measuring the current provides information on the amount of lactate. The researchers then took another step by adding a small biobattery to the device to current useable energy.
When tested on people of different fitness levels, the researchers found the least fit people produced the most lactate, which makes sense as their bodies are activating glycolysis earlier than more fit people. The maximum current was still only about 70 micro-Watts per cm2, or 4 micro-Watts, which is not much, but the researchers are confident they will be able to increase that with more work.
Source: American Chemical Society