電感電容迴路式傳感器之性能提升與應用拓展

Abstract

本論文針對電感電容迴路式傳感器進行性能提升與應用拓展，分別在感測器、致動器以及傳感系統等三方向加以研究；首先提出高靈敏度之電感電容迴路式應變計，採新型包覆式蜿蜒狀螺旋電感之設計，透過高蒲松比之材料將電感加以包覆，可增加電感受軸向應變時的截面積變化量，進而提升其靈敏度，包覆式之概念需搭配鋸齒狀螺旋電感之設計方能有效實現其效果，主要是因為鋸齒狀螺旋電感擁有較低之徑向剛性，經實驗發現，若採用傳統螺旋電感，包覆設計對其靈敏度並無提升效果(皆73.0 kHz/0.01ε)，若採用鋸齒狀螺旋電感，透過包覆設計則可將其靈敏度由62.7 kHz/0.01ε提升至121.9kHz/0.01ε，共振頻率之量測值與模擬值的誤差為5.57%，同時無線感測之能力亦成功驗證，成功實現第一個利用電感特殊幾何形狀提升其靈敏度之設計。 在電感電容迴路式致動器的部分，提出無線被動式微流體晶片，是利用多組電感電容迴路與微流體晶片的整合，藉由一組傳遞電感同時耦合多組接收電感，搭配調頻來針對特定電感電容迴路進行無線供能，進而啟動介電濕潤/介電泳晶片上的特定電極，達到微液珠/微流道之操控，成功地透過不同頻率(1210 - 1920 Hz)之訊號無線操控五組電感電容迴路，以介電濕潤實現液珠之二維傳送、切割、混合，亦利用了更高的頻率(51.2 – 76.1 kHz)驅動多組電極產生介電泳現象驅動微流道，更利用了共振頻率偏移之現象配合單一電極實現世界上第一個微流道之類比操控；由於採取一對多的電感耦合方式，此無線被動式微流體晶片可容易地被傳遞電感耦合，解決了後續應用於人體植入晶片時的內外無線耦合問題。 在電感電容迴路式傳感系統的部分，提出了一可無線感測、無線回復的碰撞紀錄開關，是利用電感電容迴路與微機電元件整合而成，當此碰撞紀錄開關受到不同程度的撞擊時，會有不同的開關切換並維持其狀態，而此狀態會影響迴路之共振頻率，因此可無線讀取之，進而得知撞擊程度，讀取完畢後，更可透過線圈對另一組電感電容迴路進行無線供電，此電能會轉換成焦耳熱驅動微機電元件中的熱致動器，進而使碰撞紀錄開關回復至初始狀態，便可進行下一次碰撞記錄，重複運作，可應用於包裹碰撞監控、建築結構內部監控等；在此以兩組卡榫分別記錄不同程度之碰撞，透過鎳基面型微加工將微機電元件加以實現，當其所承受之加速度達28.06 G時，卡榫自初始狀態切換至第一卡榫狀態，電感電容迴路之共振頻率亦從10.14 MHz切換至9.16 MHz，進一步加大加速度至37.10 G時，卡榫切換至第二卡榫狀態，電感電容迴路之共振頻率亦從9.16 MHz切換至7.83 MHz，透過無線致動對致動用電感電容迴路中產生2.07 AAC 之電流後，推動熱致動器進而使卡榫結構回復之初始狀態，電感電容迴路之共振頻率亦回到10.14 MHz，便可進行下一次的碰撞記錄，總共進行了五次碰撞記錄，成功驗證無線讀取、無線回復之碰撞記錄開關的可行性。 本論文分別在電感電容迴路式感測器、致動器以及傳感系統等三方向加以貢獻，實現了世上第一個利用特殊幾何形狀提升電感感測靈敏度之設計，以及第一個無線介電泳進行微流道驅動與類比操控，更實現了第一個整合無線電感電容感測與致動之設計，成功開發出可無線讀取、無線回復、可重複使用之碰撞記錄開關。

This dissertation focuses on the performance enhancement and novel applications of LC transducers (LC sensor, LC actuator, and LC transducing system). An LC strain sensor with a novel encapsulated serpentine helical inductor is presented. The helical coil of the inductor is formed by serpentine wire to reduce the radial rigidity. Also the inductor is encapsulated by material with high Poisson’s ratio. When an axial deformation is applied to this encapsulated inductor, the cross-sectional area of the helical coil will have more evident change due to lower radial rigidity and encapsulation. Therefore, the variation of inductance or LC resonant frequency can be enhanced to provide better sensitivity of the LC strain sensor. By using PDMS as encapsulated material, it is shown that the sensitivity of conventional helical inductor with or without encapsulation are both about 73.0 kHz/0.01ε, which means encapsulation on conventional helical inductor does not help to improve the sensitivity due to high radial rigidity of the conventional helical coil. It is also found that the encapsulated serpentine helical inductor has better sensitivity (121.9 kHz/0.01ε) than the serpentine helical inductor without encapsulation (62.7 kHz/0.01ε), which verifies the sensitivity enhancing capability of the proposed encapsulated serpentine helical inductor design. The error between simulation and measurement results on sensitivity of LC strain sensor with the encapsulated serpentine inductor is about 5.57%, which verifies the accuracy of the simulation model. The wireless sensing capability is also successfully demonstrated. For the LC actuator, a novel wireless EWOD/DEP chips is presented. The wireless EWOD/DEP chips are wirelessly powered and controlled through LC circuits with one-to-many transmitter-receiver coupling. When the input frequency is close to one of the resonance frequencies of receiving LC circuits, the induced voltage on the corresponding EWOD/DEP electrode will increase evidently due to the resonance. Therefore, the electrodes can be selectively and sequentially activated to provide sufficient EWOD or DEP forces to manipulate droplet or liquid by modulating the input frequency. Here droplet transporting, splitting, and merging are successfully demonstrated with 5 receiving LC circuits at different input frequencies (1210 Hz - 1920 Hz). The liquid pumping with multiple electrodes by wireless DEP is also demonstrated with 5 receiving LC circuits at higher input frequencies (51.2 kHz- 76.1 kHz). Furthermore, the liquid pumping with a continuous meandered electrode by wireless DEP is demonstrated through the resonant frequency shifting effect. It shows that the liquid pumping distance on a continuous electrode also can be tuned by proper frequency modulation. The transmitting inductor in the one-to-many transmitter-receiver coupling design proposed here is much larger than the total sizes of receiving inductors, therefore, receiving inductors can be easily covered and coupled by the transmitting inductor, which is a necessary feature for in-vivo applications in the future. For LC transducing system, a passive shock recorder is presented to record shock events for tens of Gs with wireless reading and wireless resetting capabilities. With a micro mechanical-latch shock switch electrically connected to a sensing LC circuit, the shock event that leads to different latching states can be recorded and wirelessly read through the LC resonance frequency. With a micro electro-thermal actuator electrically connected to a wirelessly powered actuating LC circuit, the energy can be wirelessly sent to the micro actuator to provide the necessary unlatched force. By integrating the mechanical-latch shock switch and actuator with LC circuits, the latching state can be reset through the wireless actuation. Therefore, the shock recorder can be used repeatedly, which is helpful for logistics & civil structure monitoring. Here the mechanical-latch shock switch is designed to have two-level shock recording capability. The fabrication of shock switch and actuator are achieved by Ni-based surface micromachining process. When the acceleration reaches 28.06 G, the latching state changes from the original state to the first latching state. The resonant frequency of sensing LC circuit is found to switch from 10.14 MHz to 9.16 MHz correspondingly. Further applying acceleration up to 37.10 G, the latching state changes from the first state to the second latching state, and the resonant frequency shifts to 7.83 MHz. Then, with a current 2.07 AAC wirelessly induced in the actuating LC circuit, the micro electro-thermal actuator is shown to provide sufficient displacement to reset the shock switch from latched state back to the original unlatched state, and the resonant frequency is switched back to 10.14 MHz. The fabricated shock recorder is repeatedly tested for five times. Wireless reading, resetting and shock recording capabilities are successfully verified. This dissertation focuses on the performance enhancement and novel applications of LC LC sensor, LC actuator, and LC transducing system. To the best of our knowledge, the first design that utilizes the special geometry of the inductor to enhance the sensitivity is presented here. The first wireless DEP and analogically liquid channel pumping is also realized. Furthermore, the first design that integrates both LC sensing and LC actuating capabilities is developed as a wirelessly readable and resettable shock recorder.