Fifteen-year-old Angelo Casimiro from the Philippines has just invented a smart shoe insole that produces enough electricity when you walk to charge small USB devices. The gizmo consists of piezoelectric materials, which, as Angela explains, can generate an alternating current voltage when actuated. (Solid materials like certain ceramics and salts exhibit this effect, which was discovered in the late 1800s).
Here’s a video of Angelo’s entry for the 2014 Google Science Fair:
After subjecting his insole generator to tests, he discovered that he could charge a 400 mAH Li-ion battery in full by jogging for eight straight hours. It was also possible to charge a powerbank after playing two straight hours of basketball, although the output was a bit faint. Here’s a quick video of Angelo testing the insole generator: (It’s doing great!)
You can find step-by-step instructions for making electricity generating sneakers at Angelo’s Instructables site. Here are the materials you’ll need: generic USB powerbank, piezoelectric transducers, rectifier diodes, hookup wire, some adhesive, and an old pair of shoes.
There are other power-generating, in-shoe concepts. For example, SolePower stores the energy released in each of our steps as usable electrical power; the technology works like a hand-crank flashlight. Another idea relies on a technique called reverse electrowetting: converting the energy of metal droplets in the soles into an electrical current.
Image: ASCAS via Instructables