The back-pack
The "Suspended-load" back-pack. The pack frame is fixed to the body, but the load compartment is suspended with springs from the frame. During walking, the load compartment rides up and down. To generate electricity, Rome and colleagues attached a green toothed rack to the "load plate" of the back-pack. When this toothed rack moved up and down during walking, it meshed with a gear mounted on a generator which generated electricity (Image: Science).