Image-based Multi-scale Analysis of Porous Piezoelectric Materials and Application to Bio-MIMS

新近发展起来的多孔压电材料具有许多吸引人的特性，如低Q值。然而，由于多孔PZT的微观结构尚未被三维研究，其微观结构与宏观性能之间的关系还没有被阐明，这就阻碍了材料的系统设计。因此，本研究的第一个目的在于利用X射线显微CT对三维微结构进行无损观察，基于自动图像建模的方法，对多孔PZT进行多尺度、多物理分析。为此，开发新的迭代方程求解器对于求解由体素有限元方法产生的大规模压电问题是至关重要的。该研究小组成功地开发出一种节点块预处理器。最后，在一台标准的个人计算机上分析了一个有大约一百万个有限元的问题。将其应用于具有不同孔隙率的实际多孔PZT中，并证明了其有效性。在生物微电子机械系统中的应用之一是用于健康监测系统的抽血泵。我们研究了一种大行程双压电片驱动器的结构设计。第二个应用是微针给药系统。研制了一台微针插入体外培养的人体皮肤双向受控拉伸实验装置，不仅进行了线性分析，还进行了动态分析。为了快速进行动态多尺度分析，将模型降阶方法(MOR)与有限元网格叠加法相结合进行了研究。研究发现，适当数目的基矢量可以产生足够准确的动态分析，以捕获全局和局部响应。这一结果将为未来的快速动态多尺度压电分析打开大门。

Recently developed porous piezoelectric material has many attractive characteristics such as low Q-value. However, its microstructure has not been investigated three-dimensionally yet Hence, the correlation between the porous microstructure and the macroscopic properties has not been clarified, which prevents from designing the material systematically.Therefore, the first purpose of this study lies in the multi-scale and multi-physics analysis of porous PZT based on the automatic image-based modeling by means of nondestructive observation of the three-dimensional microstructures with X-ray micro-CT. In pursuit of this, the development of new iterative equation solver is essential to solve large-scale piezoelectric problem derived from voxel finite element method. The research group succeeded in developing a node-block preconditioner. Finally, a problem with approximately one million finite elements has been analyzed on a standard personal computer. It was applied to real porous PZT with different porosity ratios, and its effectiveness has been proved.One of the applications to bio-micro-electro-mechanical-system(bio-MEMS) is a pump to draw blood for health monitoring system. We have studied the structural design of a bimorph actuator with slit to obtain large stroke.The second application is the micro-needle drug delivery system. A testing machine was developed to observe the insertion of micro-needle into cultured human skin with controlled biaxial tension.Not only the linear analysis but also dynamic analysis has been studied. For fast dynamic multi-scale analysis, the model order reduction(MOR) method has been investigated used together with one of the multi-scale methods, the finite element mesh superposition method. It was found that the appropriate numbers of base vectors in MOR can lead to accurate enough dynamic analysis to capture both global and local responses. This results will open the door to future fast dynamic multi-scale piezoelectric analysis.