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Chemists devise tattoos that produce electricity from sweat

In the future you may be able to power your phone or portable with electrical energy that you produce naturally from exercise. This potential new form of biobattery is the indirect result of the work of Dr. Wenzhao Jia and colleagues from the University of California San Diego. The prototype was presented at the Aug. 13, 2014, session of the National Meeting and Exposition of the American Chemical Society (ACS) in San Francisco.

A tattoo biosensor (enlarged above) detects lactate levels during exercise; a bio-battery using the technology could power electronics.
A tattoo biosensor (enlarged above) detects lactate levels during exercise; a bio-battery using the technology could power electronics.Credit: Joseph Wang

The original concept was to replace the necessity for a blood sample to measure lactate production in athletes. Monitoring lactate levels in athletes is necessary because lactate levels indicate the transition to glycolysis and the general fitness of an athlete. Lactate is excreted in sweat. Lactate production is also a useful indicator in many diseases.

The researchers developed a sensor that removes electrons from the lactate generated in sweat and produces a small electrical current that can be measured. The sensor can be attached to a person with temporary tattoo paper. The device allows a constant monitoring of lactate production and requires no expensive testing of blood samples. A video of the device in action can be seen here.

The researchers used their lactate monitoring device to create a sweat induced battery. Testing determined that people who exercise less can produce more power than people that exercise regularly. This seeming contradiction comes from the fact that people who exercise infrequently produce more lactate and thus more energy. The present amount of energy that is available from a single lactate sensor is 70 microwatts per cubic centimeter.

The electrical production at present is not sufficient to run a watch. The scientists reason that a larger surface area for the lactate sensor would produce more electrons and more electricity. The researchers are also planning to add an electrical storage mechanism to the system. Biobatteries like these are not toxic, recharge faster, and are renewable.