应用于无线传感网络的宽带静电式微型能量采集器研究

Nowadays, the wireless sensor networks (WSN) are still powered by conventional batteries, which limits the scale of WSN's development. A micro energy harvesting device can convert the energy from ambient environment to electric power for wireless sensors, which is a promising solution to replace the batteries and build up a self-sustainable WSN system. To extract energy from vibration sources, electrostatic energy harvesters are generally used, which are more compact and more compatible to the WSN technology comparing to the electromagnetic and the piezoelectric devices. However, most of the resonant devices have a narrow bandwidth, which limits the available vibration source. The electret materials used in the energy harvesting devices are either difficult to deposit and pattern, or easily lose the surface charge when the materials are exposed to thermal or humid environment. Furthermore, the fabrication processes for many energy harvesters are not compatible with MEMS technology, which also limits the application for WSN since most of the wireless sensors are fabricated with MEMS technology. These issues are the key issues to overcome for the development of the electrostatic energy harvesters. In this project, we will develop an electrostatic energy harvesting device based on bi-resonant structures, which will broaden the bandwidth of the device since there are two resonant frequencies for the two mass-beam systems. With the broad bandwidth, the device will keep a decent power output within a larger range of frequency. We will also develop new deposition and pattern processes for the electrets material and improve the charging efficiency and charge stability. Last but most important, we will set up a fully compatible process flow based on the standard MEMS technology, which is promising to integrate with the current WSN technology and makes a system-on-chip. This project will provide green energy for WSN and avoid the pollution from conventional batteries, which has great scientific and commercial value.

无线传感网络的能源是制约其发展规模的一个重要因素。微型静电式能量采集器可以将环境中的振动能转化为电能，替代传统电池为传感器提供能源，且有体积小、工艺兼容性高的优势。然而，目前静电式能量采集器可采集的振动频率带宽普遍较窄；此外，驻极体材料的工艺性能和充电性能也是静电式能量采集器的关键问题；最后，目前能量采集器的加工工艺与无线传感网络兼容性不好，极大地限制了其应用前景。本项目拟开发一种基于双谐振结构的静电式微型能量采集器，着重分析其动力学模型以及空气阻尼、碰撞力的影响。从而增大器件的工作带宽，使其在较大振动频率范围内均能获得理想的能量输出。本项目还将开发驻极体材料的新型加工工艺，探索电荷衰减机理，并提高其充电效率以及电荷稳定性。最终，本项目还将开发基于MEMS圆片级加工技术的工艺流程，便于与无线传感器的片上集成。项目研发的能量采集器为绿色环保能源，可避免电池污染，具有良好的学术意义和产业价值。

近年来，无线传感网络发展迅速，其能源是制约其发展规模的一个重要因素。利用MEMS技术开发的微型静电式能量采集器可以将环境中的振动能转化为电能，替代传统电池为传感器提供能源，且有体积小、工艺兼容性高的优势。在本项目开展过程中，我们开发一系列基于谐振结构的静电式微型能量采集器，着重分析其动力学模型以及空气阻尼、碰撞力的影响。从而增大了器件的工作带宽，使其在较大振动频率范围内均能获得理想的能量输出，更有利于环境中的随机振动能量采集。通过降低空气阻尼力，我们可以大幅提升单位加速度下的能量采集密度。通过研究，我们实现了3 mW/cm3/g2的单位加速度能量采集密度，比同类器件高2个数量级；并同时实现了约12Hz的器件带宽。本项目还开发了基于喷涂的驻极体材料的新型加工工艺与表面电荷图形化工艺，探索电荷衰减机理，并提高其充电效率以及电荷稳定性。此外，本项目还开发基于MEMS圆片级加工技术的工艺流程，这将便于与无线传感器实现片上集成。项目研究过程中，累计发表SCI研究论文21篇；国内外会议论文17篇，申请发明专利9项，其中已授权4项；申请并授权实用新型专利2项。大幅超过项目申请书设定目标。项目开发的能量采集器为绿色环保能源，可避免电池污染，具有良好的学术意义和产业价值。