Energy Harvesting Using Shoe Embedded with Piezoelectric Material

We have investigated the effect of the position and dimension of piezoelectric buzzers embedded in shoe soles on energy harvesting. The force and pressure generated by different types of shoes and heels were measured using plantar measurement systems. A Kistler force plate and zebris force distribution measurement provided precise values and locations of the force and pressure exerted by the foot on the sole. The position and area of buzzers inside the sole of the shoes resulted in a significant increase in electrical outputs. A maximum open-circuit voltage of 38 V, short circuit current of 33 μA, and harvested energy of 296.8 μJ cm−3 were found across a 100-μf capacitor for a wedge-heeled shoe. The open-circuit voltage in the wedge-heel type of shoe improved by more than five times when the pressure is changed from the heel to the toe and area of the buzzer is increased. Similarly, the energy stored across a 100-μF capacitor also improved by five times for the same shoe. Furthermore, the short circuit current improved by three times when the shoe was changed from a wedge heel to a block heel. The results indicate that this technique can be used to power wearable electronics and sensors.