In the future, working up a sweat by exercising may not only be good for your health — but it could also power your small electronic devices through new technology. Researchers reported last month that they have designed a sensor in the form of a temporary tattoo that can both monitor a person’s progress during exercise, and produce power from their perspiration.

The device works by detecting and responding to lactate, which is naturally present in sweat. “Lactate is a very important indicator of how you are doing during exercise,” explained Wenzhao Jia, Ph.D. The more intense the exercise, the more lactate the body produces.

A prootype of the tattoo is pictured below:

[Image Credit: Joe Wang, ACS]
[Image Credit: Joe Wang, ACS]
During strenuous physical activity, the body needs to generate more energy, so it activates a process called glycolysis. Glycolysis produces energy and lactate, the latter of which scientists can detect in the blood.

Professional athletes monitor their lactate levels during performance testing as a way to evaluate their fitness and training program. In addition, doctors measure lactate during exercise testing of patients for conditions marked by abnormally high lactate levels, such as heart or lung disease.

Power generated via the biobattery varied depending on the individual, the report explains:

When 15 volunteers wore the tattoo biobatteries while exercising on a stationary bike, they produced different amounts of power. Interestingly, people who were less fit (exercising fewer than once a week) produced more power than those who were moderately fit (exercising one to three times per week). Enthusiasts who worked out more than three times per week produced the least amount of power. The researchers say that this is probably because the less-fit people became fatigued sooner, causing glycolysis to kick in earlier, forming more lactate. The maximum amount of energy produced by a person in the low-fitness group was 70 microWatts per cm2 of skin.