Displacement-Amplified Piezoelectric Heel Charger to Generate Power On-the-go

Abstract

Our daily walking activity provides a sustainable and promising power source for instantly charging mobile devices. However, the low-frequency small deflection nature of walking force imposes great challenges for efficient energy harvesting. To address such challenges, this paper presents a solution relying on a heel charger to lever a multilayer-piezoelectric-bimorph to amplify the input force defection and therefore convert the kinetic energy to electricity in a much more efficient manner. The proposed heel charger can be easily integrated into the shoe and the piezoelectric bimorphs are clamped to a pivot at one end and pined on the other. A rigid short lever beam is excited by the walking force and its defection reflected on the long lever beam will be amplified to bend the piezoelectric bimorphs for power generation. Experiments show that, when exposed to an excitation of 2.8 mm at 2.3 Hz, the heel charger with 3 layers of the piezoelectric bimorphs produces the RMS power of 4.0 mW and the peak power of 17.5 mW, in comparison to the RMS power of 2.3 mW and the peak power of 8.2 mW for that with the single layer piezoelectric bimorph. And thus, the heel charger with more layers can potentially produce more power output, which indicates the great potential of this technology for power on-the-go.