Energy Harvesting based on Ferroelectrets with Transverse Piezoelectric Effect

收集环境中可利用的能源并将其转化为电能，对于为传感器网络和数据传输提供能量正变得越来越重要。可能的应用是监视和传输人类生活功能或远程对象的重要测量数据。在这个项目中，我们将使用两种不同类型的铁驻极体薄膜样品和新的器件配置来研究铁驻极体能量收集器。在过去的几年里，我们已经证明，收割机利用铁驻极体的纵向压电效应(D33)，提供约1微瓦的电力，地震质量为1微克，正弦加速度相当于重力。然而，利用横向压电效应(D31)在优化的具有平行隧道铁驻极体的能量收集器中，最近在相同的条件下实现了高达2兆瓦的功率输出。这些结果是用一台尺寸只有8×5毫米的能量收集器获得的，目前还没有发表。首先，我们将改进现有的平行隧道铁驻极体，我们将研究一种新的管状空气腔方法，在该方法中，几个氟乙烯(FEP)管将被热熔化形成铁驻极体薄膜。然后，通过将这些新材料与不同膜型能量收集结构中的地震质量相结合，我们将研究与前面工作中使用的能量收集装置相比有显著改进和改进的能量收集装置。此外，还将研究一种基于悬臂结构的新型能量收集装置。这种结构将由金属或聚合物悬臂梁组成，在悬臂梁上安装软铁驻极体和地震质量块。这种方法有两个优点：1)可以独立选择主要由悬臂决定的机械性能。这使我们能够优化悬臂梁，例如，对于低共振频率和大挠度。2)针对悬臂梁弯曲过程中隧道厚度变化较大的情况进行设计，可以独立地最大化软铁驻极体的压电活性。通过将硬悬臂梁和软铁驻极体相结合来分离这些功能是我们建议的项目的一个很有前途的想法，应该会产生更大的电力输出。对于我们的新类型的上述器件，它可以独立调节谐振频率和压电活性，目前还没有得到任何实验结果。然而，我们的估计表明，这种新型设备的输出功率约为几兆瓦。因此，我们的新收割机很可能会比现有的基于陶瓷的悬臂装置性能更好。

Harvesting environmentally available energy and converting it to electrical energy is gaining increasing importance for energizing sensor networks and data transmission. Possible applications are monitoring and transmitting human life functions or important measurement data of remote objects. In this project, we will be studying ferroelectret energy harvesters using two different types of ferroelectret film samples and new device configurations. In the last couple of years, we have demonstrated that harvesters, utilizing the longitudinal piezoelectric effect (d33) of ferroelectrets, deliver about 1 µW of electrical power with a seismic mass of 1 g and a sinusoidal acceleration corresponding to gravity. However, using the transverse piezoelectric effect (d31) in optimized energy harvesters with so called parallel tunnel ferroelectrets, a power output of up to 2 mW was achieved under the same conditions recently. These results, obtained with an energy harvester with a size of only 8 mm x 5 mm, have not been published yet. First, we will improve the existing parallel tunnel ferroelectrets and we will investigate a new tubular air cavity approach, in which several fluorethylenpropylen (FEP) tubes will be thermally fused to form a ferroelectret membrane. Then, by combining these new materials with a seismic mass in various membrane type energy harvesting configurations, we will investigate energy harvesting devices which are significantly improved and modified compared to those used in our aforementioned work.Further, a new class of energy harvesting devices, based on a cantilever structure, will be investigated. This structure will consist of a metal or polymer cantilever beam onto which the soft ferroelectret and a seismic mass is mounted. This approach features two advantages: 1) An independent choice of the mechanical properties, primarily determined by the cantilever, can be made. This allows us to optimize the cantilever e.g. for low resonant frequencies along with large deflections. 2) The piezoelectric activity of the soft ferroelectret can be maximized independently by designing for large change in tunnel thickness during cantilever bending. Separating these functions by combining the hard cantilever with a soft ferroelectret is one of the promising ideas of our proposed project and should result in large electrical power output.For our new class of aforementioned devices with its independent adjustment of resonance frequency and piezoelectric activity, no experimental results have been obtained yet. However, our estimates indicate a power output from such novel devices in the order of several mWs. Thus, our new harvesters will most likely outperform existing ceramic-based cantilever devices.