前中 一介

第38回「センサ・マイクロマシンと応用システム」シンポジウムは，令和3年11月9日～11日の3日間，オンラインにて開催された。本シンポジウムは，電気学会センサ・マイクロマシン部門の部門大会であり，第12回マイクロ・ナノ工学シンポジウム（日本機械学会 マイクロ・ナノ工

© Published under licence by IOP Publishing Ltd. Piezoelectric MEMS energy harvesters based on multilayer (ML) Pb(Zr,Ti)O3 (PZT) thin films with interdigitated electrodes (IDE) as their internal and top electrodes are proposed and designed. Thick PZT thin films with good piezoelectric characteristics can be deposited by using multilayer deposition technique. Furthermore, IDE is adopted to the harvester design in order to take advantage of the longitudinal piezoelectric effect, which typically has twice piezoelectric constant as large as transverse effect. The energy harvesters with two electrode configurations, parallel plate electrodes (PPE) and IDE, are designed and estimate these output power. According to the result of finite element analysis, the output power per gravitational acceleration is about 124 μW for the PPE configuration. On the other hand, the output power per gravitational acceleration for the IDE configuration is about three times as large as that for PPE. Moreover, the influence of IDE patterns and the number of PZT layers were investigated. The larger number of layers results in the larger output power.

In this study, we have fabricated membranes which are composed of two-and four-layer Pb(Zr, Ti)O-3 thin films with internal electrodes by using sputtering depositions. Electrical and driving characteristics as ultrasonic transducers of these membranes are evaluated. By increasing number of layers, the static displacement is reduced. However, for the multilayered membrane, the dynamic displacement became large because of the large mechanical Q factor in resonant vibration. The emitted sound pressure level and characteristics of the ultrasonic transducer are estimated. (C) 2018 Wiley Periodicals, Inc.

In the past 30 years, remarkable progress has been made in the field of MEMS sensors. The journal Sensors and Materials has reached its 30th year and has been documenting the progress of microsensor technology. Also, I have been working on MEMS sensors for around 30 years, and watching the progress of the MEMS field. Recently, almost all physical sensors have been realized by MEMS technology and many dreams and expectations in the old days have become real devices. In this paper, I will focus on intelligence or smartness of sensors as the subject with some historical aspects.

For the first time, it is experimentally validated that the output voltage from series-connected piezoelectric elements on MEMS structure can be multiplied without degradation. The output voltage has been degraded for conventional devices (piezoelectric voltage-output sensors) based on the series-connected piezoelectric elements because of parasitic capacitances. The elimination of the parasitic capacitance by using not Si but polymer for structural material achieves output voltage multiplication.

In this study, we report the design and fabrication results of an optimized curved beam structure for low frequency, under one-hundred Hz, and non-linear operation of MEMS (Micro-Electromechanical Systems) vibration energy harvester. The optimization procedure for shape and dimension of the curved beam were established combining a FEM and a numerical analysis. Simulated curved beam with bi-stable motion was evaluated for wide bandwidth operation of a vibration energy harvester and preliminary fabrication process was confirmed.