Frequency-band programmable piezoelectric energy harvesters with variable substrate material, tip mass and fractal architectures: Experimental and numerical investigations

To automate the approach of assessing the health and efficacy of large structural systems globally through structural health monitoring systems, a vast network of sensors that must be mounted throughout the entire structure and connected to a continuous power supply is necessary. Clusters of wires need to be placed throughout the structures to support the network, or batteries must be changed frequently, adding to the network's high maintenance expenses. The present study investigates the scope of powering such lowenergy devices with a localized renewable energy source based on smart piezoelectric components such as PZT-patched energy harvesting systems. This paper analyses the performance of the PZT patch mounted on different structures that are predominantly activated in d 31 mode. A vibration testing rig is manufactured to perform experiments for investigating the effect of material properties, natural frequencies, vibrating structural mass, and their interaction with the output power of a PZT transducer. Optimal mass, material, and structural configurations are attempted to be identified experimentally. The hypothesis, predictions, and results are evaluated further based on a converged finite element model. Subsequently, we introduce a novel concept of chiral fractal substrates in piezoelectric energy harvesters, wherein a significant improvement is noticed in the energy output along with increased frequencyband programmability. The power output of such architected and optimized energy harvesters holds the potential to serve as a reliable and sustainable alternative to conventional batteries, effectively providing a renewable source of power to energize and sustain low-power micro-electro-mechanical systems (MEMS) and devices.