室溫量測之被動式表面聲波無線氫氣感測器

Abstract

在面臨能源危機的時代，使用清潔能源的汽車已逐漸成為日後發展的主流，其中氫氣即為備受矚目的替代能源之一，然而氫氣具有無色無味的特性，且濃度在介於4%到75%時會有自燃或是爆炸的危險性，因此氫氣偵測的工作亦開始受到重視。在氫氣儲存和運送的過程中，即時地監測氫氣濃度對於環境保護及人身安全都非常的重要，在此使用具有無線傳輸能力的氫氣感測器便可提供極佳的便利性，此外無須電池的被動式氫氣感測器，更可免除更換電池的困擾且降低系統成本。因此為了提高量測便利性及減少成本的考量，便開啟了被動表面聲波式無線氫氣感測器的研發。 本文中使用了中心頻率為433MHz的128°YX-LiNbO3做為表面聲波識別標籤之基板，再附加一個電阻式氫氣感測器，已成功整合成阻抗加載型的被動表面聲波式感測器。此量測系統的優點如下：無線傳輸，被動式架構，以及為質輕微小之元件。 首先，本論文藉由耦合模型理論而設計出表面聲波識別標籤之相關參數，並模擬得知其所對應之頻率響應，再由快速傅立葉轉換得到識別標籤的時間域訊號。接下來則製作一電阻式感測器，其中感測材料需具有高穩定度、重複使用性以及製程簡便等優點，因此選定氧化鋅奈米柱，而為了讓本架構可在常溫下使用，故於奈米柱之上鍍白金作為催化劑。之後，將電阻式感測器和表面聲波識別標籤接合，以組合出阻抗加載型的被動表面聲波式感測器。最後，即結合感測器及量測腔體以完成實驗架設。由實驗結果可知：本感測器對於氫氣具有極佳的靈敏度，且有重覆使用性。

For an energy crisis, the clean fuel is gradually taken seriously. Hydrogen is an alternative energy source, and now hydrogen vehicles are not a reality but a product on the market. Hydrogen gas is colorless, tasteless and flammable. When concentrations of hydrogen are between 4% and 75%, hydrogen is subject to combustion and explosion risk. During the process of hydrogen gas storage and transportation, monitoring the condition of hydrogen gas is important for environmental protection and human safety. Besides, it is convenient to use a hydrogen sensor, especially the passive wireless hydrogen sensor. A passive device doesn’t need a battery, and the cost will be reduced greatly. Hence, the passive wireless hydrogen SAW sensor is developed for its convenience and low cost. In this thesis, an impedance-loaded SAW sensor is achieved by combining the SAW tag whose substrate is the 433MHz 128˚ YX-LiNbO3 and a resistive hydrogen sensor. First, the coupling-of-modes model is used to design the parameters of the SAW tag and predict the frequency response. Then, by employing the fast Fourier transform the signals in time domain can be obtained. The resistive hydrogen sensor whose sensing film is the Pt-coated ZnO nanorods has the advantages of high stability, repeatability and easy fabrication. Finally, the sensor is formed and measured to evaluate performances. The results show that this SAW sensor has good repeatability and high sensitivity, and its advantages are wireless transmission, passive mode and mini size.