表面聲波元件因為其具有體積小、價格便宜、高靈敏度及高再現性，所以經常會被使用於化學感測的應用。在文獻資料中，表面聲波感測器無論在氣態環境下及液態環境下的分子檢測都有相當良好的表現。而表面聲波感測器感測的主要機置來自於質量加載效應、黏彈性效應及聲電效應。這些效應都會引起表面聲波感測器的波傳速度變化及聲波能量的變化。這些效應的產生主要來自於表面聲波元件中的化學塗層。而這些塗層是一些具有選擇性和再現性的生物或化學塗層。本研究主要探討這些塗層的效應，並建立一套完整的表面聲波感測系統。這些研究主要區分為下列項目:
1.當聚合物（polymer）被當成生物塗層，彈性效應的擾動就會變的明顯，所以一般的質量加載分析就沒辦法進行較完整的分析。因此Martin and Frye的彈性效應分析加上Auld的擾動定理就被拿來做表面聲波元件的黏彈效應分析。這個研究將會推導這個分析的理論。
2.聚合物切變模數（shear moduli）和塊體模數（bulk moduli）的在感測的影響也會在這個研究中進行討論。從計算的結果看出，塊體模數對感測的影響是可以被呼略的，所以可以自行設定成常數。而如果只研究聲波元件的波數變化，切變模數的虛部是可以被忽略兒設成常數的。而將Y-Z的鋰酸鈮（LiNbO3）塗上三種不同化學塗層（glassy、glassy-rubbery及rubbery）製成有機磷酸分子感測器的研究中發現glassy-rubbery型態的塗層有比較好的特性。
3.另外我們對ST-cut石英的黏彈特性進行討論及研究。在研究結果得到了部份結論，基於靈敏度、聲波消散及溫度穩定性的考量，在氣態環境下，ST-X石英塗上glassy-rubbery型態的化學塗層的感測器會有最佳的特性。
4.另外，環境因素（如濕度和乙醇等）的影響也會被研究。研究發現，如果使用ST-X石英做為表面聲波感測器，當FPOL膜厚為0.02、0.017及0.015m時，如各別選用105-130MHz、125-155MHz和140-175MHz等操作頻率會有最小的濕度效應。而高頻的表面聲波感測器，最好還是使用在乾燥的環境。
5.雷利波（Rayleigh-wave）在液態操作下，會產生大量的能量損耗而無法使用。但是水平剪力波（SH-SAW）在液態環境中確不會有大量能量損耗。基於這項原因，水平剪力波的表面聲波元件被選為要開發的表面聲波感測器基板。而我們選用的是Y36o-X 的鉭酸鈮（LiTaO3）為基版。
6.表面聲波感測器的指叉電極和反射電極的保護，我選用了具光靈敏度的聚蔥亞胺（polyimide）來保護。為了降低表面聲波感測器的雜訊干擾，我在元件上使用了電性隔離通道並將兩通道接地分開。在系統設計上，溫度不穩定的問題，我使用了一個高精度的溫度控制器和一個溫度補償的數學方法來解決。我們在這個研究中開發了一套全新而穩定的表面聲波感測系統。
7.這個新系統，我們設計了兩套實驗來驗證，一個為酒精濃度檢測，另一個為液體分類。實驗結果，濃度百分之8.75的酒精會有103.5ppm的反應，且可重覆使用，而其雜訊（noise level）約為0.7ppm。因此，其訊雜比（signal-to-noise ratio）約為148。另一項實驗結果，這機台成功的分辨水、生理食鹽水、運動飲料及柳橙汁。
8.最後我們用將表面聲波元件塗上導電性的薄膜作為氨氣的感測器，這導電性的薄膜為聚苯胺（polyaniline）。實驗結果發現，這個氨氣感測元件於攝氏25度下的靈敏度約為0.23 deg/ppm且其最小可量測程度為0.07ppm。所以塗上導電性的薄膜的表面聲波氨氣感測器在室溫下量測氨氣上，有著相當優異的表現。

　　Surface acoustic wave (SAW) devices are favored for use in chemical sensing applications because of their small size, low cost, high sensitivity, and reliability. Details, regarding SAW devices can be found elsewhere and feasibility of using SAW structure for vapor and liquid molecule detection has been examined as well. Various effects, including mass loading, viscoelastic (elastic) effect loading and acouto-electric coupling, contribute SAW sensor response. SAW sensors vary the SAW phase velocity and attenuation as the vapor adsorbs in the chemical interface. The chemical interface is chemical or biochemical compounds over the SAW propagation path, and selectively and reversibly interacts with the specific analyte vapor and liquid molecule. This investigation is focusing on properties of the chemical or biochemical interface and establishing a complete SAW sensor system. The study was divided into several items as follows.
1.When the polymer coating is used, however, the elastic loading also contributes to the perturbation and the mass loading analysis is not enough. Hence, the Martin and Frye’s method and Auld’s perturbation theory used for research of viscoelastic effects on SAW device are presented.
2.The effects of polymer parameters (shear moduli and bulk moduli) in sensing application are discussed in the investigation. From the calculation result, the bulk moduli can be assumed as the constant. And the effect of imaginary of shear moduli can be neglected when the investigation is focusing on velocity change. The viscoelastic effect in Y-Z LiNbO3 with three kinds of polymer (glassy, glassy-rubbery, and rubbery) as the chemical and organophosphorous sensor is discussed in this study. The glassy-rubbery film seems like a good choice for SAW sensor application.
3.The viscoelastic effect in ST-quartz is also discussed in this investigation. From the calculation result, when sensitivity, acoustic wave dissipation and temperature stability are all considered in gaseous phase detection, the optimum suggestion of SAW sensor design should include glassy-rubbery polymer as the chemical interface and ST-X quartz as the substrate.
4.The influences of environment factors (for example humidity and ethanol) are also investigated. When the ST-X quartz is used as the substrate of SAW sensor, the operating frequency ranges with negligible humidity effect in common environment are 105-130MHz, 125-155MHz, and 140-175MHz for FPOL films of thickness 0.02, 0.017, and 0.015m, respectively. For suppressing humidity interference, a higher operating frequency of the SAW sensor is better to be used in the drier humidity.
5.The Rayleigh-wave presents the very high decay and the SH-SAW presents a less energy decay when operating in liquid phase. For this reason, the SH-SAW device is selected to be used in gaseous and liquid phase application and The Y36o-X LiTaO3 was selected as the substrate of the SH-SAW sensor chip.
6.For SH-SAW sensor chip design, the photosensitive polyimide is used to protects the IDTs and reflector of SH-SAW sensor. Otherwise, isolation gap and independent ground pad are applied in the SH-SAW sensor chip to reduce the noise influence. For SH-SAW sensor system design, the temperature un-stability is solving by a precious temperature controller and a mathematic temperature compensation method. A novel steady on SH-SAW sensor system is developed in this investigation.
7.This improved SH-SAW sensor system was applied in ethanol vapor detection and liquid identification. The response to 8.75% ethanol was 103.5ppm and reversible clearly and the noise level was 0.7ppm. Hence, the signal to noise ratio was about 148. Besides, it clearly identified the saline solution, ion supply water, and orange juice. The long-time stability is also verified.
8.The conductivity polymer is successfully used in SH-SAW sensor chip as the ammonia sensor and the conductivity polymer is polyaniline. The sensor presented a sensitivity of 0.23 deg/ppm at 25oC and the minimum detection level was estimated to be 0.07 ppm at 25oC. However, the SH-SAW coated with PANI exhibited an excellent response for detecting ammonia at room temperature.

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