Researchers at the University of California San Diego have created what they have termed a "wearable microgrid," a smart shirt which harvests and stores energy from the human body — taking as its input both motion and the wearer's sweat.
"We're applying the concept of the microgrid to create wearable systems that are powered sustainably, reliably and independently," explains co-first author Lu Yin of the team's work. "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."
The prototype microgrid, developed by a nanobioelectronics team led by Professor Joseph Wang, takes the form of a shirt with flexible electronics printed on top. Energy is harvested in two ways: Triboelectric generators capture energy from the wearer's arm movements as they walk or run; biofuel cells capture the wearer's sweat and turn it into electricity.
"When you add these two together, they make up for each other's shortcomings," claims Yin. "They are complementary and synergistic to enable fast startup and continuous power." The captured energy, meanwhile, is stored in a series of supercapacitors attached to the outside of the shirt, from where it can be called upon to drive wearable electronics.
In testing, the wearable microgrid was put through 30-minute sessions of either cycling or running followed by 20 minutes of resting. During these tests, the system harvested enough energy to power an LCD wristwatch or an electrochromic display — providing the core concept.
"We're not just adding A and B together and calling it a system," claims Yin. "We chose parts that all have compatible form factors (everything here is printable, flexible and stretchable); matching performance; and complementary functionality, meaning they are all useful for the same scenario (in this case, rigorous movement). [Also,] we are not limiting ourselves to this design. We can adapt the system by selecting different types of energy harvesters for different scenarios."
The team's work has been published in the journal Nature Communications under open-access terms.