微結構液動耦合效應之研究

On the Hydrodynamic Coupling Effect of Microstructures

李俊宏(Jiunn-Horng Lee)

指導教授 ： 方維倫

國立清華大學/工學院/奈米工程與微系統研究所/博士(2010年)

摘要

微機電系統工程使用微加工製程技術製作特殊的微結構，並和相關之控制電路整合，經由利用其中微結構的動態特性以執行特定之致動或感測的功能，這些微機電致動器或感測器的動態特性與其微結構的動態能量損失息息相關，尤其許多微致動器或感測器有時因為成本的考量或是使用上的需要而必須在大氣環境下操作，此時其最大的動態能量損失因子來自其微結構與周遭空氣交互作用所產生的空氣阻尼，因此，微結構與其周遭氣體互動耦合效應之研究對微元件之設計係非常重要的課題。本文首先介紹微結構動態能量損失形成的相關機制及其與微結構動態特性之關係，並整理探討其有關之研究。接著以實驗方法研究微懸臂樑在自由空氣空間振動的空氣阻尼來驗證流固耦合數值分析方法和現有近似解析模型的適用性，並根據實驗結果，修正現有近似的解析模型，提出一估算微懸臂樑品質因子的半經驗公式，使其能更準確預估微懸臂樑的品質因子，以協助進行微懸臂樑相關的應用設計。最後研究應用微結構液動耦合的效應來調控微懸臂樑的品質因子，利用三根微懸臂樑陣列結構之外側兩微懸臂樑振動所產生之流體動力，來改變位於中央之微懸臂樑的空氣阻尼大小，進而調控其動態反應，並以磁致動微懸臂樑陣列液動耦合的相關實驗，探討如何透過微懸臂樑陣列中微懸臂樑之間距、相對的振動相位和驅動力大小等的調變，來調控位於中央之微懸臂樑的品質因子，以符合設計所要求之動態特性。

關鍵字

微懸臂樑陣列 ； 微機電 ； 品質因子 ； 空氣阻尼 ； 流體動力

並列摘要

The dynamic behavior of microelectromechanical systems (MEMS) devices is closely related to their energy losses during their operations. As MEMS devices operate at atmospheric pressure, air damping is the dominant factor for energy loss. Therefore, it is very important to study the fluid-structure interaction effect of microstructures to evaluate their dynamic responses, and it is of useful to tune their quality factors to further control their dynamic performances. Firstly, this study presents a review of current research on the mechanisms of dynamic energy dissipation in MEMS devices. Then, this study employs experimental methods to investigate the air damping of micro-cantilevers in free space to validate numerical approach and existing approximate models. Based on the experimental results, the study proposes a modified model which can precisely predict the quality factors of the micro-cantilevers in a free air space. Finally, this study experimentally investigates the effect of hydrodynamic coupling of a micro-cantilever array on the dynamic response of a micro-cantilever. The micro-cantilever array consists of three harmonically driven micro-cantilevers dynamically coupled through air flow. The right cantilever and left cantilever (auxiliary-cantilevers) adjacent to the middle cantilever (operating-cantilever) are exploited to generate hydrodynamic force to change the air damping of operating-cantilever. Thus, the quality factor of operating-cantilever can be controlled by changing the phase and magnitude of excitation force on auxiliary-cantilevers, and varying the gap between auxiliary-cantilevers and operating-cantilever.

並列關鍵字

Micro-cantilever array ； MEMS ； Quality factor ； Air damping ； Hydrodynamic force

參考文獻

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