A comprehensive review on mechanical amplifier structures in piezoelectric energy harvesters

This paper presents a comprehensive review of structural optimization for the piezoelectric energy harvesters by summarizing the characteristics, working principles, advantages, disadvantages, performance, evaluation factors, and potential applications of each amplifier structure. This includes the cantilever, flexure structure, combined structure, multistage structure, and derivative designs such as compound and hinge designs. Examples and optimization method of structural design which utilizes the compressive mode, 33-mode configuration, and stacking design of piezoelectric material is provided. The power output, amplification ratio, and the applied mechanism theory of each structure are then compared and discussed to ease the benchmarking process for future research.