Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : November 25, 2025 - November 29, 2025
In recent years, demands for MEMS devices have increased rapidly with the spread of IoT. As demands for devices increase, demands for batteries also increase. While the advantage of batteries is that they have excellent mobility, the disadvantage is their high environmental impact. Therefore, we focus on energy harvesting instead of batteries. Energy harvesting is a method of converting unused energy such as light, heat, and vibration into electrical energy. In energy harvesting, we focus on vibration power generation using piezoelectric materials. Piezoelectric materials make it possible to convert mechanical energy into electrical one. Among the three types of working principles using piezoelectric materials, the piezoelectric stack is selected. The reason why we focus on the stack is that it has a relatively high piezoelectric coefficient and can function even under high compressive loads. However, the harvested energy is usually low if the input force is directly acting on the stack.
Because the deformation amplitude of the stack is low owing to its high stiffness. Therefore, a force amplification mechanism is adopted to increase the load acting on the stack. The force amplification mechanism allows to increase the compressive load on the stack. Among the force amplification mechanisms, a two-stage diamond-shaped mechanism harvester composed of two-stage frames is used. In compression tests, the performance of the stack and harvester has been clarified. The results indicate that the voltage increases proportionally with the applied load. In addition, the force amplification ratio of the harvester, which indicates the ratio of the output force to the input one is about 3 times higher. The results indicate that the proposed harvester features large amplification ratio and compact size, and it is possible to amplify the power generation capacity of the stack by about 3 times.
