Energy Harvesting based on Ferroelectrets with Transverse Piezoelectric Effect

收集环境可用的能量并将其转换为电能对于激励传感器网络和数据传输越来越重要。可能的应用是监测和传输人类生命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电驻极体薄膜样品和新的设备配置来研究铁电驻极体能量采集器。在过去的几年里，我们已经证明，利用铁电驻极体的纵向压电效应（d33），收割机可以在1 g的地震质量和与重力对应的正弦加速度下提供约1 µW的电力。然而，在具有所谓的平行隧道铁电驻极体的优化能量收集器中使用横向压电效应（d31），最近在相同条件下实现了高达2mW的功率输出。这些结果是用尺寸仅为8 mm x 5 mm的能量采集器获得的，尚未发表。首先，我们将改进现有的平行隧道铁电驻极体，我们将研究一种新的管状空气腔的方法，其中几个氟乙烯丙烯（FEP）管将热熔合，形成一个铁电驻极体膜。然后，通过将这些新材料与各种膜式能量收集结构中的振动质量相结合，我们将研究与我们上述工作中使用的能量收集装置相比有显着改进和修改的能量收集装置。此外，将研究基于悬臂结构的新型能量收集装置。该结构将由金属或聚合物悬臂梁组成，其上安装有软铁电驻极体和地震质量。这种方法具有两个优点：1）可以独立选择主要由悬臂梁确定的机械性能。这使我们能够优化悬臂，例如，低谐振频率沿着与大偏转。2)在悬臂梁弯曲过程中，通过设计隧道厚度的大变化，可以独立地最大化软铁电驻极体的压电活性。通过将硬悬臂梁与软铁电驻极体相结合来分离这些功能是我们所提出的项目的有前途的想法之一，并且应该会产生大的电功率输出。对于我们的新一类上述器件，其谐振频率和压电活性独立调节，尚未获得实验结果。然而，我们的估计表明，从这样的新型设备的功率输出在几个mW的顺序。因此，我们的新收割机将很可能优于现有的陶瓷悬臂设备。

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.