Inspired by community microgrids
“We’re applying the concept of the microgrid to create wearable systems that are powered sustainably, reliably and independently. 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 Lu Yin, a nanoengineering Ph.D. student at the UC San Diego Jacobs School of Engineering.
Energy from sweat and swinging
This T-shirt captures energy in two ways. It has biofuel cells that harvest energy from sweat inside the shirt at the chest. And two, the shirt has triboelectric generators placed on the outside of the shirt on the forearms and sides of the torso near the waist. They harvest energy from the swinging movement of the arms against the torso while walking or running.
“When you add these two together, they make up for each other’s shortcomings,” Yin said. “They are complementary and synergistic to enable fast startup and continuous power.” The entire system boots two times faster than having just the biofuel cells alone, and lasts three times longer than the triboelectric generators alone.
Devices printed onto a T-shirt
And finally, the shirt is also able to store energy. Supercapacitors on the outside temporarily store energy from both energy-generating devices and then discharge it to power small electronics like smart watches and bicycle computers. The wearable microgrid is built from a combination of flexible electronic parts and each is screen-printed onto a shirt and placed in a way that optimises the amount of energy collected.
Cycling in this T-shirt powers a watch
The high-tech shirt was tested during 30-minute sessions that consisted of 10 minutes of either exercising on a cycling machine or running, followed by 20 minutes of resting. The bioenergy T-shirt was able to power an LCD wristwatch throughout each 30-minute session.
How does it work?
The biofuel cells are equipped with enzymes that trigger a swapping of electrons between lactate and oxygen molecules in human sweat to generate electricity. The triboelectric generators are made of a negatively charged material, placed on the forearms, and a positively charged material, placed on the sides of the torso. As the arms swing against the torso while walking or running, the oppositely charged materials rub against each and generate electricity.
“Imagine the biofuel cells are like a slow flowing faucet and the triboelectric generators are like a hose that shoots out jets of water,” he said. “The supercapacitors are the tank that they both feed into, and you can draw from that tank however you need to.”
Any bike-packers or bike tourers interested in a jersey that creates energy out of movement and sweat?