Sensitivity evaluation of a Love wave sensor with multilayer structure for biochemical application

摘要

This paper presents a sensitivity evaluation of a love wave sensor with multilayer structure consisting of polymethyl methacrylate (PMMA)/SiO_2/41° YX LiNbO_3. A theoretical model is presented to describe wave propagation in love wave devices with multilayered structure on large piezoelectric substrate. A complex dispersion equation expanded into Taylor series was presented to describe the lossy mechanism of the PMMA layer. Using the gold film as the sensitive interface, the mass loading sensitivity of the love wave sensor for biochemical application was evaluated theoretically, and the effects from the SiO_2 and PMMA on the sensor sensitivity were investigated to allow the design of an optimized structure. From the calculated results, the optimal thicknesses of SiO_2 and PMMA in the multilayered structure were determined, and the sensitivity comparison between love waves in LiNbO_3/SiO_2/PMMA and LiNbO_3/PMMA was studied, which shows that there is larger mass loading sensitivity in love wave devices with multilayered structure.