Your brutal gym workouts in the not-too-distant future could power your electronic devices.

In the latest of a series of exciting innovations unveiled at the American Chemical Society meeting in San Francisco, scientists have presented a tattoo biobattery fueled by the lactate present in sweat after intense exercise.

"Our device is the first to use sweat. It's a proof of concept," said Dr. Wenzhao Jia of at the University of California, San Diego.

"At the moment, the power is not that high—only four microwatts. But we are working on enhancing it so it can power small electronic devices."

The team of researchers initially intended to develop a wearable lactate sensor, which they achieved by building one into temporary-tattoo paper.

"I've worn it myself; you don't even feel it," Jia told BBC News. "It really is like a tattoo."

Another layer of sophistication was added to the invention when Jia and her colleagues incorporated an enzyme capable of stripping electrons from secreted lactate, which generated a weak electrical current.

Test subjects on exercise bikes were reportedly able to generate up to 70 microwatts per square centimeter of skin. Interestingly, the less fit among them were able to generate more electricity. The simple explanation is that if you're not in such great shape, less activity is required for you to start forming lactate.

"A fit person is going to have to work out much harder to power the battery," Jia explained.

The next step in the process is figuring out a way for this wearable biobattery to generate more electricity, possibly by making the strips more sensitive to lactate.

If all goes according to plan, you will eventually become your own renewable energy source. For better or worse.