Imagine you are out for a run with tunes fuelling your stride. Suddenly, your earbuds run out of juice and your good vibes come to a screeching halt. "Ugh," you groan as you look to your activity tracker for encouragement, only to realise it's dead too.
Nanoengineers at the University of California San Diego reckon they have developed a solution that harvests and stores human energy to charge small electronic devices.
The robot-chic look is a microgrid made of flexible, electronic parts screen printed onto a shirt. The three main elements are sweat-powered biofuel cells, motion-powered triboelectric generators, and supercapacitors to store the collected energy.
And the entire thing is washable – if you don't use detergent.
The researchers say the main innovation is the efficient integration of the devices, not the wearable itself. The design allows for continuous power by utilising multiple energy sources providing different voltages, they added.
"Just like a city microgrid integrates a variety of local, renewable power sources like wind and solar, a wearable microgrid integrates devices that locally harvest energy from different parts of the body, like sweat and movement, while containing energy storage," said co-first author and nanoengineering PhD Yu Lin.
The triboelectric generators start converting movement to high voltage energy at the onset of exercise by taking advantage of arm movement while running or walking. Negatively charged material on the inner forearms rubs against positively charged material on the sides of the torso to generate the power.
Once the sweating starts, the biofuel cells stitched inside the shirt collect the sweat. Enzymes in the biofuel cells trigger a swapping of lactate and oxygen electrons in the perspiration to generate low-voltage electricity.
The supercapacitors collecting the energy are located on the chest and combine the different voltages then connect to the wearer's devices.
Testing included the successful powering of either an LCD wristwatch or small electrochromic display. The testing went on for 30 minutes of exercise and 10 minutes of rest. There was no testing on more demanding devices like smartphones so for now you'll have to remember to charge that one yourself. ®