Single crystal piezoelectric transducers to harvest vibration energy

Advances in low power design open the possibility to harvest energy from the environment to power electronic circuits. Electrical energy can be harvested from various transducers including piezoelectric materials. Piezoelectric materials can be used as mechanisms to transfer mechanical energy usually ambient vibration into electrical energy that can be stored and used to power other devices. It has been found that a piezoelectric device attached to a beam with cantilever boundary conditions provides an effective configuration for capturing transverse vibrations and converting them into useful electrical power. Piezoelectric thin films attached to a silicon beam also have attracted attention for energy harvesting applications. In this paper, we present the results of a preliminary study of the effect of vibration amplitude on the performance of a PMN-PT single crystal beam with interdigitated electrodes pattern. The structure is used to demonstrate that feasibility of a novel piezoelectric monomorph cantilever beam for producing high AC voltage. The energy harvesting capability of a PMN-PT cantilever beam is tested on a 10mm-long and 1.2mm-wide rectangular prototype made out of 0.1mm-thick PMN-PT film with interdigitated electrodes. The experiments are performed to test the level of AC voltage and current generated from the PMN-PT cantilever beam device when subjected to transverse vibration of varying amplitude at the first mode of the resonant frequency. The frequency response of the monomorph prototype shows that the first mode resonance frequency of the excitation model is approximately 190Hz. We found that increasing the poling voltage also causes increased output AC voltage magnitude. These tests show that a significantly high AC voltage of 13V was achieved with 50μm shaker displacement. The measured RMS current was ~20μA.