The advancement in the field of wireless electronics for use in embedded systems and control system technologies is limited by the availability of efficient and portable power generation system. Harvesting ambient energy provides an excellent option to energize these low power wireless electronic applications. Low frequency vibrational energy scavenging of microelectromechanical system (MEMS) utilizing piezoelectric power generation can effectively serve this purpose. Initial fabrication has been carried out in terms of PZT film characterization, initial testing to verify the piezoelectric nature of the as coated PZT film, optimization of 125 μm thick nickel electroplating, and innovative cantilever release process based on inductively coupled plasma etching (Bosch Process) to increase the yield of working cantilever arrays on a die. An optimized process flow for the prototype fabrication was proposed and lead zirconium titanate (PZT) thin film deposition by sol-gel was characterized on three different bottom electrodes. The net effective yield in terms of working cantilevers on a die was increased to about 80% of over 500 cantilevers on a die. X-ray diffraction results revealed the perovskite phase formation of the as-coated PZT film with a  predominant crystal orientation. The as-coated PZT film was poled and the initial testing confirmed the piezoelectric nature of the film. The desired cantilever configuration was modeled such that its natural frequency lies approximately in the 200 Hz range while ensuring that the maximum stress generated in the structure does not exceed the yield strength of the material both in the static stage and in the dynamic stage. It was observed that positioning of the mass was a significant factor influencing the natural frequency of the structure. The analysis was performed for cantilever configurations made of silica, PZT, and nickel in which the effect of the thinner layers (electrodes) has been ignored. It was found that this configuration yields a natural frequency of 255 Hz which lies in the desired range of frequency (100-500 Hz).
Dynamic Modeling and Prototyping for Low-Frequency Piezoelectric MEMS Vibration Energy Scavenging: VibES
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Mukherjee, R, & O'Neal, CB. "Dynamic Modeling and Prototyping for Low-Frequency Piezoelectric MEMS Vibration Energy Scavenging: VibES." Proceedings of the ASME 2006 International Mechanical Engineering Congress and Exposition. Microelectromechanical Systems. Chicago, Illinois, USA. November 5–10, 2006. pp. 307-315. ASME. https://doi.org/10.1115/IMECE2006-14349
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