具正反器特性之微機電式雙穩態元件

Abstract

本研究系研發製作一新型微機電式雙穩態之驅動裝置「單鍵驅動微機電式正反器」，僅需要單一驅動電壓以及相同驅動時間即可切換雙穩態機構之兩個穩態，為全世界第一個以單鍵驅動實現Push-On-Push-Off以及相同驅動電壓的微機電開關元件。由於其雙穩態的特性、狀態切換條件的一致性，可應用於機械式正反器之發展。此裝置由兩組雙曲型樑(Centrally clamped double curved beam)及一組Ｖ型樑致動器(V-beam actuator，VBA)所組成，此兩組雙曲型樑分別連接一扭矩推桿以及彈簧推桿。此驅動裝置之操作分為兩部分，雙穩態機構由第一穩態跳躍至第二穩態為Push-On，當雙穩態機構由第二穩態被釋放回第一穩態為Push-Off。在Push-On操作時，施加電壓於Ｖ型樑致動器，加熱產生熱形變並推動上曲型樑的扭矩推桿，形成力矩驅動雙曲樑結構但第一穩態(Off-State)跳躍(snap through)至第二穩態(On-State)時，彈簧推桿會碰觸Ｖ型樑致動器，由於其撓性大可穩定切換至第二穩態。Push-Off操作時，施加相同之電壓以及時間於Ｖ型樑致動器，產生位移推擠彈簧推桿，其造成的力矩使雙曲樑機構由第二穩態被釋放回到第一穩態。此裝置結構之設計乃是架構於物理模型的推導並且配合數值模擬之結果來進行設計。製程相當簡單，只需要單一光罩並採用SOI 晶圓，以標準化微機電製程ICP-RIE加工。 此裝置Push-On及Push-Off的操作方式同正反器的時脈輸入，輸入相同電壓、相同脈衝時間的方波訊號，即有On/Off切換現象。經實驗初步測試後，尺寸2000μm的元件輸入頻率62.5赫茲、佔空率50%、12伏特的clock訊號，可使元件連續執行Push-On以及Push-Off的動作，亦即元件可執行最高頻率31.25赫茲On/Off的完整操作。

This paper presents the first MEMS fully compliant bistable device that only requires one actuator for switching between its two stable states using single driving voltage with the same actuation duration. Based on these characteristics, the device is in fact a mechanical flip-flop which is analogous to the flip-fop device in electronics. The proposed device employs a mechanically Push-On-Push-Off mechanism consisting of two curved beam structures. An integrated V-beam actuator is used as the only actuation component. The proposed device can be easily realized on an SOI wafer by using the ICP-RIE process with a single photomask. Preliminary measurement results show that a 62.5 pulse frequency of 12 V with 50% duty cycle applied to the V-beam actuator can continuously switch the device between the On state and the Off state. Transient displacement results measured by using a vibrometer are also provided. The bistability of a pre-shaped buckled beam with elastically constrained boundary conditions was also studied theoretically and experimentally. The buckled shape model, which characterizes the initial buckled deflection, is employed in this study. A systematic method of designing a bi-stable buckled beam has been developed and applied to the bistable switch mechanism and the torque rod mechanism. The method is validated with the results by FEM simulations. The proposed analytical models were also in good agreement with measured results.