Study of multi-functional surface acoustic wave sensor using Langmuir-Blodgett (LB) method

介绍了一种声表面波(SAW)传感器及其环境测量系统。声表面波器件已被广泛用作环境测量的化学和物理传感器。通常，大多数用作传感器的SAW器件都被涂覆了一层薄膜，该薄膜能够通过物理和化学吸收与感兴趣的化学物质相互作用。传感器的灵敏度、响应时间和重复性与敏感膜的特性密切相关。因此，选择性镀膜对于SAW传感器的稳定性和重复性是非常重要的。选择性薄膜的镀膜方法有很多，如空气刷涂法、浸渍镀膜法和旋涂法等，这些方法都具有很好的重复性。超薄有机薄膜目前在集成光学、传感器和纳米技术等许多领域都受到了人们的关注。超薄FILL…自组装(SA)法和Langmuir-Blodgett(LB)法制备的膜更多。在128 Y切X向传播的LiNbO_3衬底上制作了SAW延迟线，并在传播路径上涂覆了用这种转移技术沉积的选择性聚合物。以聚苯乙烯磺酸钠为SA膜材料，以磷脂酰乙醇胺为LB膜材料。由于分子的吸附，这些选择性薄膜的密度、介电常数和电导率都发生了变化。实验结果表明，声表面波速度的变化与有机气体的浓度成正比。利用单层薄膜可以获得快速、完全可逆的响应。结果表明，该薄膜具有良好的线性度、高灵敏度和快速响应特性，并利用反射式延迟线设计了一种新型的功能传感器。在36YxLiTaO_3衬底上制作了一条反射SH-SAW延迟线，其直角(90度)边缘被用来反射SAW。在一个衬底上制作了六通道反射延迟线。每个通道具有不同的长度，并且在时间域中获得响应。测量了每个延迟线上反射声表面波的相位和幅度作为传感器的响应，并通过几个实验验证了边缘反射传感器的性能。通过测量SH-SAW入射到垂直角时反射波的幅度和相位，得到了反射式SAW传感器的基本特性。研究结果表明，反射式SH-SAW传感器对气液两相的传感是非常有效的，为反射式SH-SAW传感器的有效工作提供了无线系统。提出了一种用于精确测量多通道传感器反射波相位特性的电子测量系统。结果表明，该无线传感系统非常适合遥感应用。最后介绍了无线SH-SAW传感器在样品液体电导率和粘度测量中的一些应用。较少

A surface acoustic wave(SAW) sensor and its system for measuring the environment are presented. SAW devices have been widely used as a chemical and physical sensor for measuring the environment. In general most of the SAW device using as the sensor is coated with a thin film that capable of interaction with the chemical of interest through physical and chemical absorption. Sensitivity, response time, and reproducibility of the sensor are closely related with the characteristics of the sensing film. Therefore, the selective coating film is very important for a stability and reproducibility of the SAW sensor. There are numerous methods to coat a selective film, such as air brushing, dip cast, and spin coating of the SAW devices with good reproducibility.In this paper, first the SAW sensor incorporating an ultra thin selective film is presented. Ultra thin organic films are currently gaining interest in many areas such as integrated optics, sensors, and nano technology. The ultra thin fil … More ms were made by both self-assembled(SA) method and by Langmuir-Blodgett(LB) method. SAW delay lines were fabricated on a 128 Y cut X propagating LiNbO3 substrate and the propagation path was coated with the selective polymer deposited by these transfer technique. The polystyrene sulfonic acid sodium was used as an SA film material and the phosphatidylethanolamine was used as a LB film material. Due to sorption of molecules, the density, permittivity and electrical conductivity of these selective film change. The effects caused to reduce the velocity of the SAW Experimental results showed that the SAW velocity change was quite linear in proportion to the concentration on organic gases. Rapid and totally reversible responses were obtained by using the thin monolayer film. Moreover, it is shown that the thin film is suitable to obtain good linearity, high sensitivity and rapid response.Moreover, a new functional sensor also has been designed by using reflecting delay line. A reflecting SH-SAW delay line was constructed on a 36 YX LiTaO_3 substrate and the right angle(90-degree) edge has been used to reflect the SAW. Six-channel reflecting delay lines have been fabricated on one substrate. Each channel has a different length and the responses are obtained in time domain. Both the phase and amplitude of the reflected SAW on the each delay line were measured as a sensor response.Several experiments were performed to verify the performances of the edge reflection sensor. The basic characteristics of the reflecting SAW sensor were obtained by measuring the amplitude and phase of reflected wave when the SH-SAW is incident to a perpendicular corner. The obtained results showed that the reflecting SH-SAW sensor was very effective for sensing the gas and liquid phase.Wireless systems are also suggested for the effective operation of the reflecting SH-SAW sensor. The electronic measurement system for accurately measuring the phase characteristics of a reflected wave from the multi-channel sensor is proposed. In particular, it is shown that the wireless sensing system is very suitable for remote sensing. Finally it will be shown some applications of the wireless SH-SAW sensors on the measurement of the conductivity and viscosity of sample liquids. Less