Guided Shear Horizontal Surface Acoustic Wave Sensors for Chemical and Biochemical Detection in Liquids

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• 作者：Fabien Josse ; Florian Bender ; and Richard W. Cernosek
• 刊名：Analytical Chemistry
• 出版年：2001
• 出版时间：December 15, 2001
• 年：2001
• 卷：73
• 期：24
• 页码：5937 - 5944
• 全文大小：122K
• 年卷期：v.73,no.24(December 15, 2001)
• ISSN：1520-6882

文摘

The design and performance of guided shear horizontalsurface acoustic wave (guided SH-SAW) devices on LiTaO₃substrates are investigated for high-sensitivity chemicaland biochemical sensors in liquids. Despite their structural similarity to Rayleigh SAW, SH-SAWs often propagate slightly deeper within the substrate, hence preventingthe implementation of high-sensitivity detectors. Thedevice sensitivity to mass and viscoelastic loading isincreased using a thin guiding layer on the device surface.Because of their relatively low shear wave velocity, variouspolymers including poly(methyl methacrylate) (PMMA)and cyanoethyl cellulose (cured or cross-linked) areinvestigated as the guiding layers to trap the acousticenergy near the sensing surface. The devices have beentested in biosensing and chemical sensing experiments.Suitable design principles for these applications arediscussed with regard to wave guidance, electrical passivation of the interdigital transducers from the liquidenvironments, acoustic loss, and sensor signal distortion.In biosensing experiments, using near-optimal PMMAthickness of ~2 m, mass sensitivity greater than 1500Hz/(ng/mm²) is demonstrated, resulting in a minimumdetection limit less than 20 pg/mm². For chemical sensorexperiments, it is found that optimal waveguide thicknessmust be modified to account for the chemically sensitivelayer which also acts to guide the SH-SAW. A detectionlimit of 780 (3 × peak-to-peak noise) or 180 ppb (3 ×rms noise) is estimated from the present measurementsfor some organic compounds in water.