Fabrication of High-Quality Piezoelectric Micro Energy Harvester and of 3-1, 3-3 Mode Optimization

With the advent of the Internet of Things (IoT) era, more and more sensing units will be connected to the internet. While this improves quality of life, the extra sensors will, however, cost more electrical energy consumption. If each sensing unit has a self-powered generation system, whose power source is entirely from the environment, high cost batteries or cord connections will not be needed. According to past studies, the energy density of vibration sources is the highest available in our society and is practically inexhaustible. For this reason, this study is focused on the development of piezoelectric energy harvesters (EH) reaping energy from vibrations. Over the past few years, the majority of selected materials used to make EH are a type of lead zirconate titanate (PZT). As time progresses, research teams improve the output performance of EH through changing fabrication processes. Until now, the performance of EH energy output had gradually reached the limit of the chosen materials. In our previous research, a significant power output increase and durability improvements were caused by altering the EH substrate material. Therefore, this study suggests that only the introduction of innovative materials will allow a breakthrough in the limit of EH energy output. According to recently published literature, attention has been given to lead magnesium niobate–lead titanate (PMN-PT) material because of its high piezoelectric constant and electromechanical coupling factor. It has become highly desirable as the next-generation piezoelectric material. In this study, an introduction of piezoelectric ceramic material will be presented first. Theory regarding cantilever piezoelectric EH is elucidated with a focus on the 3-1 and 3-3 operation modes. The reasonable simplification of EH analysis is presented for the benefit of EH designers estimating the output performance in a practical amount of time. Next, measured parameters are used for EH analysis to show the theory corresponds to experimental results. To demonstrate EH performance by experiment, 2.8 um of PMN-PT film was successfully deposited on a stainless steel substrate by aerosol deposition. The microstructure of the ceramic powder and piezo-film were analyzed, assisting in the understanding of suitable powder conditions for aerosol deposition. With the help of micro electro-mechanical systems (MEMS) technology processes, this study produced PMN-PT based EHs and optimized the annealing temperature and poling condition of EH devices. The experimental results show that the device has a maximum output power of 8.423 uW with a resonant frequency at 94.8 Hz under 0.5 g acceleration. The output performance is better than the PZT-based EH with the same thickness. When given a comparison with previous work, the volumetric power density in this study is also better than those previously found.