Scientists have developed a wearable device that could generate energy from the swing of an arm while walking or jogging. The research was published in the journal Advanced Functional Materials. The device, about the size of a wristwatch, produces enough power to run a personal health monitoring system.
Energy-harvesting devices are in high demand to power the millions of devices that make up the internet of things, researchers said. By providing continuous power to a rechargeable battery or super capacitor, energy harvesters can reduce the labour cost of changing out batteries when they fail and keep dead batteries out of landfills, they said.
Certain crystals can produce an electric current when compressed or they can change shape when an electric charge is applied. This piezoelectric effect is used in ultrasound and sonar devices, as well as energy harvesting.
The researchers used a well-known piezoelectric material, PZT, and coated it on both sides of a flexible metal foil to a thickness four or five times greater than in previous devices.
The compressive stresses that are created in the film as it is grown on the flexible metal foils also mean that the PZT films can sustain high strains without cracking, making for more robust devices.