穿戴式軟性機電複合微結構之設計與分析

Soft electromechanical, composite microstructures

蘇煥然(Su, huan jan)

指導教授 ： 蘇育全

國立清華大學/原子科學院/工程與系統科學系/碩士(2014年)

https://doi.org/10.6843/NTHU.2014.00330

摘要

本實驗室透過設計並製造了內含微米孔洞的PDMS 結構，並佈植雙極性電荷於孔洞內部的上下表面，如同駐極體可以提供特定方向的永久電場。由於該材料的有低的楊氏係數，並透過填入高分子材料PTFE可使孔洞表面擁有高電荷特性，使該結構在受垂直應力時，因結構變形導致電場的變化提供機械能與電能之間的能量轉換，使該結構如同壓電材料具有壓電特性和高的壓電係數(壓電薄膜)。除了透過重直方向的施力取得功率，該裝置也可以應用於橫向的拉伸進行能量收集。由於PDMS孔洞結構有幾何參數可以調整的特色，本論文使用COMSOL有限元素法軟體去分析牆狀與柱狀結構在d33 的工作原理和物理現象，分析不同幾何形狀的電場分佈、電極表面的電荷密度、應力變化和d33數值走勢，處理靜電場與力學的耦合問題，並引用多項參數建構出可以得到與COMSOL數值解相同的d33分析模型，可以從該模型找出不同參數之於壓電係數的影響和結構最佳化的趨勢。由於PDMS的材料特性有很高的Poisson's ratio(接近~0.5)，除了有不可壓縮的性質，還有良好的可撓曲性與穿戴於身體上的優勢。本論文分析在不同幾何參數下的d31數值走勢，同時也建構出d31分析模型。最後發現當孔隙率越高，牆狀結構可以表現更強的壓電特性和拉伸性。當壓電薄膜有良好d31、d33的壓電係數可以從人體運動取得能量轉換的方式更加廣泛。

關鍵字

COMSOL ； PDMS ； 壓電係數

並列摘要

It has been demonstrated experimentally that charge implanted composite microstructures exhibit desirable piezoelectricity (with a piezoelectric coefficient d33 higher than 1500 pC/N) and stretchability (with an elastic modulus about 300 kPa). The implanted charge pairs function as dipoles, which response promptly to diverse electromechanical stimulation. Until now, only limited analytical and numerical models have been developed to characterize the complex electromechanical responses of such microstructures. To address the need, an analytical model with key parameters estimated by a finite element model has been built. In this paper, regular column- and wall-type cellular structures with micrometer-sized voids that allow better modeling and optimization are studied, and both 33 and 31 coupling modes are considered. It is demonstrated that cellular structures with higher porosity usually exhibit stronger piezoelectricity and higher stretchability.
Furthermore, thickness ratios of the multilayer microstructures are found to be crucial to their characteristics. The physics and electromechanical properties of the charge implanted composite microstructure can be understood and optimized accordingly. As such, they could potentially serve as flexible and sensitive electromechanical materials, and fulfill the needs of a variety of sensor and energy harvesting applications

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