Multifunctional self-charging structures using piezoceramics and thin-film batteries

Multifunctional material systems combine multiple functionalities in a single device in order to increase performance while limiting mass and volume. Conventional energy harvesting systems are designed to be added to a host structure in order to harvest ambient energy surrounding the system, but often cause undesirable mass loading effects and consume valuable space. Energy harvesting systems can benefit from the introduction of multifunctionality as a means of improving overall system efficiency. This paper presents the investigation of a novel multifunctional piezoelectric energy harvesting system consisting of energy generation, energy storage, and load bearing ability in a single device. The proposed self-charging structures contain piezoelectric layers for power generation, thin-film battery layers for energy storage, and a central metallic substrate layer, arranged in a bimorph configuration. Several aspects of the development and evaluation of the self-charging structure concept are reviewed. Details are provided on the fabrication of a piezoelectric self-charging structure. An electromechanical model is employed to predict the response of the harvester under harmonic base excitation. Experimentation is performed to confirm the ability of the device to simultaneously harvest and store electrical energy. Finally, both static and dynamic strength analyses are performed to determine the load bearing ability of the structure.