Enhanced piezoelectric energy harvesting based on sandwiched phononic crystal with embedded spheres

Abstract

In recent years, metamaterial/ phononic crystal (PnC) based energy harvesters are gaining interest due to their excellent elastic wave manipulation and energy trapping capabilities. Here, we propose a novel PnC comprising of Tungsten Carbide (WC) spheres embedded in epoxy resin matrix. The sphere-epoxy composite is encapsulated by Aluminum (Al) holey structure and the device is sandwiched between two Al plates. Numerical analysis of band structure reveals a wide phononic band gap (BG) from 50.65 kHz to 71.12 kHz. These BGs can be engineered by varying geometric parameters of the unit cell viz., the radius of the sphere and thickness of Al plates. A point defect is introduced by removing the central sphere of the 5 × 5 PnC to facilitate the robust localization of evanescent wave defect modes within the bandgap. Moreover, it is observed that, by altering the radius of the defect sphere, the number of defect modes and their shift can be reconfigured. A PnC based energy harvester is implemented by attaching a piezoelectric disk (PZT-5H) onto the defect PnC just above the defect site. This arrangement of PZT disk converts the highly resonant mechanical defect mode into electrical energy, thereby allowing vibration energy harvesting. Finally, we show that the power enhancement can be achieved by ∼12 times with the proposed PnC compared to the bare Al block.