Gao has developed a new way to power wireless wearable sensors: He harvests kinetic energy that is produced by a person as they move around.
“Our triboelectric generator, also called a nanogenerator, has a stator, which is fixed to the torso, and a slider, which is attached to the inside of the arm. The slider slides against the stator during human motion, and, an electrical current is generated at the same time,” Gao says. “The mechanism is quite simple. Friction results in electrical generation. This is not something new, concept-wise.”
This energy harvesting is done with a thin sandwich of materials (Teflon, copper, and polyimide) that are attached to the person’s skin. As the person moves, these sheets of material rub against a sliding layer made of copper and polyimide, and generate small amounts of electricity. The effect, known as triboelectricity, is perhaps best illustrated by the static electric shock a person might receive after walking across a carpeted floor and then touching a metal doorknob.