Towards high power output electrostatic energy converters

用于包括与物联网相关的应用的各种应用的无线传感器的领域正在快速增长。使用可更换电池为无线设备供电将变得不可持续，因为它们的寿命有限且维护成本高。因此，非常需要微型发电机，其不显眼且便宜，同时产生足够的功率以匹配无线传感器的要求。硅基静电发电机采用可变电容器来收集机械振动能量。与其他机械振动收集技术相比，它们具有显着的优势，因为它们与集成电路（IC）制造工艺兼容，从而最大限度地降低成本，并允许与无线传感器和控制电路进行片上集成。目前，最先进的收割机的功率输出水平仍然比大多数先进的超低功率无线系统所需的功率输出水平低一个数量级。在这项工作中，将研究新的概念，以创建具有更高功率输出的硅基静电收割机。 作为该项目的一部分，将持续努力吸引代表性不足的少数民族学生参加研究。研究结果还将通过伦斯勒理工学院的暑期项目和其他外展活动传达给包括高中生在内的广大受众。本提案的目的是研究硅基静电振动能量采集器的新方法，以增加其功率输出。这种装置通常采用具有叉指电极的可变电容器，其中一组电极响应于振动而移动。转换的能量取决于运动期间电容变化的水平。所提出的工作探索了两种变革性的方法，以增加电容变化，从而提高功率水平，通过调查：i）双层制动器，结合间隙闭合交叉指型平面内收割机中的高密度填充电极，以及ii）平面外交叉指型收割机。第一种方法采用两种不同的停止机制，纳米停止器和软停止器，它们一起工作以提高最大电容并产生频率上转换，从而增加间隙闭合平面内采集器的每单位时间的能量转换周期数。纳米阻挡层由沉积在电极侧壁上的具有纳米厚度的绝缘膜限定，其设置绝对最小间隙。与经由光刻和蚀刻限定的止挡件相比，薄膜止挡件将提供小至少一个数量级的分离间隙。这又导致电容变化的数量级增加，从而导致功率输出的数量级增加。软止动器的作用是触发频率上转换，增加收获频率，沿着增加器件带宽，并通过最小化冲击力延长纳米止动器的寿命。第二种方法采用了一种以前没有探索过的结构，用于硅基设备的振动能量收集。这种结构在平面外振荡，并且由于能够经历极端电容变化而具有高转换潜力。为了验证这些方法，将开发理论模型来预测作为输入参数的函数的性能。将对这两种类型的器件进行设计优化，然后进行制造和测试。

The field of wireless sensors for various applications including applications related to the Internet of Things is rapidly growing. Powering wireless devices with replaceable batteries will become unsustainable due to their finite lifespan and high maintenance costs. Thus, there is a great need for micro-scale power generators, which are inconspicuous and inexpensive while generating sufficient power to match the requirements of wireless sensors. Silicon-based electrostatic power generators employ variable capacitors to harvest mechanical vibration energy. They have significant advantages over other mechanical vibration harvesting technologies because of their compatibility with processes for fabrication of integrated circuits (IC), which minimize costs and also allow for on-chip integration with wireless sensors and control circuitry. Currently, the level of power output of state-of-the art harvesters is still an order of magnitude lower than that required by most advanced ultra-low power wireless systems. In this work, new concepts will be investigated to create silicon-based electrostatic harvesters with increased power output. As part of the project, a consistent effort will be made to attract students from underrepresented minorities in the research. The research results will also be communicated to a broad audience including high school students, through summer programs and other outreach efforts at Rensselaer Polytechnic Institute. The objective of this proposal is to investigate new methods for silicon-based electrostatic vibration energy harvesters in order to increase their power output. Such devices typically employ variable capacitors with interdigitated electrodes, where a set of electrodes moves in response to vibration. The energy converted depends on the level of capacitance variation during motion. The proposed work explores two transformative approaches to increase the capacitance variation, and consequently the power level, by investigating: i) a dual-level stopper, in conjunction with highly dense packed electrodes in gap-closing interdigitated in-plane harvesters and ii) out-of-plane interdigitated harvesters. The first approach employs two different stopping mechanisms, a nanostopper and a soft-stopper, that work together to boost the maximum capacitance and produce frequency up-conversion, increasing the number of energy conversion cycles per unit time for a gap closing in-plane harvester. The nanostopper is defined by an insulating film with nanometer thickness deposited on the electrode sidewalls, which sets the absolute minimum gap. The thin film stopper will provide a separation gap that is smaller by at least an order of magnitude, as compared to stoppers defined via lithography and etching. This in turn results in an order of magnitude increase in capacitance variation and consequently in power output. The role of the soft-stoppers is to trigger frequency up-conversion, increasing the harvesting frequency, along with increasing device bandwidth and prolonging the lifespan of the nanostopper by minimizing impact forces. The second proposed approach employs a structure not previously explored for vibration energy harvesting with silicon-based devices. This structure oscillates out-of-plane and has high conversion potential due to the ability to undergo extreme capacitance changes. To validate these approaches, theoretical models will be developed to predict performance as a function of input parameters. Design optimization will be carried out for both types of devices, followed by fabrication and testing.