声表面波气相色谱仪在禁毒工作中的应用初探

声表面波气相色谱仪具有灵敏度高、色谱柱升温速度快(~20?C/s)、体积小等特点,可实现痕量气体的广谱(挥发和半挥发性有机物)、快速(<5 min)、高灵敏度(ppb^ppt级)现场分析,可应用于地下制毒工场/窝点探查、毒驾与吸毒人员筛查等方面。该文介绍了该课题组在甲基苯丙胺(冰毒)检测、羟亚胺制作窝点现场检测方面的研究进展。

基于新型声表面波单端对谐振器的生物传感器

该文设计并制作了一种基于新型声表面波(SAW)单端对谐振器的金黄色葡萄球菌生物传感器,该传感器采用了叉指电极中间内置敏感区域的谐振器结构。首先基于微扰理论分析了SAW生物传感器的响应机理。然后结合耦合模理论分析,得到了该谐振器的频率响应曲线。通过网络分析仪测量,实际制作的SAW谐振器的频率响应与仿真结果一致,且具有高品质因数的优点。实验中采用该结构对金黄色葡萄球菌进行初步检测,结果表明检测结果线性度较好,为下一步实现SAW传感器特异性实时检测金黄色葡萄球菌奠定了基础。

Fast calculate the parameters of surface acoustic wave coupling-of-modes model

Accurate solutions of acoustic waves in piezoelectric substrate and metal film as layered structure were obtained. Phase velocity, electromechanical coupling coefficient and static capacitance were calculated based upon the solutions. Chen and Haus＇ theory was used to analyze surface acoustic waves in shorten gratings with single finger every period and a reflection coefficient expression of one strip was presented. Parameters of aluminum on X-112°Y LiTaO3 and gold on ST-quartz were calculated. The results agreed well with those from Ken-ya Hashimoto＇s theory. The reflection coefficient of gold on ST-quartz was measured to verify the theoretical result.

Theoretical and experimental study on strip reflection coefficient of different crystal symmetry class

The closed-form expressions on strip reflection coefficients of tetragonal 4/mmm, hexagonal 6/mm and trigonal 3m crystal, etc, were derived, which are different from that of cubic m3m crystal published. The reflection coefficients of short-circuited Al grating and groove grating on 112° rotated X-cut Y-propagation LiTaO3 are then given. The reflection property of a short-circuited Al -recessed groove grating on 112°LiTaO3 has been experimentally studied and the condition without internal reflection was achieved. It concludes that the structure of single finger without internal reflection can be realized by the short-circuited Al -recessed groove grating on 112°LiTaO3 and thereafter a pass-band filter with central frequency at 255 MHz, bandwidth about 10 MHz, pass-band ripples less than 0.4 dB was yielded.

Research on the temperature characteristic of Love wave device with structure of multi-waveguides used for gas sensor

This paper aimed at extracting optimal structural parameters for Love wave device with structure of multi-waveguides to improve its temperature stability. The theoretical model dealing with the Love wave propagation in multi-waveguides was established first, the dispersion characteristic is depicted by the acoustic propagation theory of stratified media and boundary conditions. Combing with the dispersion characteristics and Tomar＇s method, the optimal structural parameters for the Love wave device with zero temperature coefficient were extracted, and confirmed by the following experimental results. Excellent temperature coefficient of the Love wave device with SU-8/SiO2 on ST-90°X quartz substrate was evaluated experimentally as only 2.16 ppm/℃, which agrees well with the calculated results. The optimized Love wave device is very promising in gas sensing application.

Development of two-port surface acoustic wave resonator with Al/Au electrodes for gas sensing

Simple and efficient surface acoustic wave （SAW） two-port resonators with low insertion loss and high Q-values on ST-X quartz substrate using a corrosion-proof A1/Au-stripe electrode structure are developed for gas sensing. It was composed of two shorted grating reflectors and adjacent intedigital transducers （IDT）, and an active metal film in the cavity between the IDTs for the sensitive film coating. The devices are expected to provide good protection towards metal electrode for gas sensors application in chemically reactive environments. Excellent device performance as low insertion loss, high Q factor and single-mode are achieved by carefully selecting the metallic electrode thickness, cavity length and acoustic aperture. Prior to fabrication, the coupling of modes （COM） model was performed for device simulation to determine the optimal design parameters. The fabricated single-mode SAW resonator at operation frequency of 300 MHz range exhibits matched insertion loss of ~6.5 dB and loaded Q factor in the 3000 range. Using the fabricated resonator as the feedback element, a duaresonator-oscillator with excellent frequency stability （0.1 ppm） was developed and evaluated experimentally, and it is significant for performance improvement of SAW gas sensor.

Finite difference time domain analysis of two-dimensional surface acoustic wave piezoelectric phononic crystals at radio frequency

The finite-difference time-domain （FDTD） method is proposed for analyzing the surface acoustic wave （SAW） propagation in two-dimensional （2D） piezoelectric phononic crystals （PCs） at radio frequency （RF）, and also experiments are established to demonstrate its analysis result of the PCs＇ band gaps. The FDTD method takes the piezoelectric effect of PCs into account, in which periodic boundary conditions are used to decrease memory/time consumption and the perfectly matched layer boundary conditions are adopted as the SAW absorbers to attenuate artificial reflections. Two SAW delay lines are established with/without piezoelectric PCs located between interdigital transducers. By removing several echoes with window gating function in time domain, delay lines transmission function is achieved. The PCs＇ transmission functions and band gaps are obtained by comparing them in these two delay lines. When Aluminum/128°YX-LiNbO3 is adopted as scatter and substrate material, the PCs＇ band gap is calculated by this FDTD method and COMSOL respectively. Results show that computational results of FDTD agree well with experimental results and are better than that of COMSOL.

On propagation characteristics of SH-type surface acoustic waves in periodic metal gratings by variational principle

Based on D.P. Chen and Haus＇ theory, a theoretical method was presented to analyze dispersion characteristics of SH-type surface acoustic waves （SAWs） propagating on periodic metallic grating structures with a variational principle and coupling-of-modes equation. Without using complicated Green＇s function, the calculating results of the method agree well with those of Hashimoto＇s theory. On the other hand, Hashimoto＇s method is helpless for calculating the dispersion relation of short-circuited gratings on ST-90°X quartz etc. However, the method developed in this paper can successfully calculate it.