Piezoelectric based energy harvester embedded in shoe for wearable electronics
Piezoelectric based energy harvesting has become a popular research interest for last few years. This is due to the increasing demand for low-powered portable and wearable electronic devices such as health monitoring sensors. This paper presents two polyvinylidene fluoride (PVDF) based energy harvesters, which can be embedded in shoes to generate electric energy while human walking. One of the harvesters is specially designed as a sandwich structure, placed under the ball of foot, while the other one has curved or oval-shaped structure, placed under the heel of foot. Both harvesters are developed and deployed appropriately in the sole to couple maximum mechanical stress to the piezo-material and achieve high power output. The system was analysed, using mathematical modelling and results are verified by performing experiments in the lab. It has been observed experimentally that sandwich structured harvester produces 4.9 μW across a capacitor of 10 μF while walking at a speed of two step/second (2 Hz). However, for the same capacitor, the curve-shaped harvester produces up to 5.625 μW power. Integrated output power of both energy harvesters was 9.625 μW .