An electrostatic energy harvester with sandwiched structure of two electret layers

Abstract

View the article online for updates and enhancements. Abstract. In this paper, we proposed a fully packaged sandwich electrostatic energy harvester, which consists of two opposite charged electret layers to improve the output performance of the packaged device. The new device is based on the out-of-the-plane gap closing scheme, and the main components are similar to our previous research. This sandwich device mainly contains two variable capacitors, and the volume of the device is about 1.3 × 1.8 × 0.15 cm 3 . Because of the complementation between the two opposite charged variable capacitors, the output performance of the overall sandwich device is better than the single electret layer devices. We have achieved a maximum power output of 20.78 μW at the acceleration of 19.96 m/s 2 , which is almost 1.4 times of the packaged single capacitance structure, without changing the overall volume of the packaged device. Also, this sandwich device shows good performance at random vibration. IntroductionWith the growth of the internet of things (IOT), the low power wireless sensors are used more and more frequently, and a perpetual power for the low power sensors is an urgent need. So, micro energy harvesters as the self-sustainable power sources for the low power systems have attracted much attention. The vibration energy harvester is one of the micro energy harvesters, and it can convert the kinetic energy from ambient environment into electric energy. According to the principle of energy conversion, different kinds of vibration energy harvesters have been designed and studied, like electromagnetic vibration energy harvester [1]-[4], piezoelectric vibration energy harvester [5]-[10], and electrostatic vibration energy harvester [11]-[22]. Among these vibration energy harvesters, the electrostatic energy harvester is easier to fabricate and to integrate with the micro systems through the simple Si-based MEMS technology. With the advanced MEMS technology, the electrostatic energy harvester takes the advantages of small size, high energy density, high conversion efficiency, and long-term output stability [23].Up to now, there are a lot of reports about the electrostatic vibration energy harvesters which mainly focuses on three different configurations of variable capacitors by changing the gap distance [11]-[17], changing the overlap area [18], [19], or changing the counter electrodes [20]-[22]. In most of these studies, the main purpose is to improve the power output or bandwidth of the device to get a higher power density at a wider bandwidth. In our previous study, a four-wafer stacked electrostatic