Abstract
Love wave sensors have been widely used for sensing applications. In this work, we introduce the theoretical analysis of the monolayer and double-layer waveguide Love wave sensors. The velocity, particle displacement and energy distribution of Love waves were analyzed. Using the variations of the energy repartition, the sensitivity coefficients of Love wave sensors were calculated. To achieve a higher sensitivity coefficient, a thin gold layer was added as the second waveguide on top of the silicon dioxide (SiO2) waveguide–based, 36 degree–rotated, Y-cut, X-propagating lithium tantalate (36° YX LiTaO3) Love wave sensor. The Love wave velocity was significantly reduced by the added gold layer, and the flow of wave energy into the waveguide layer from the substrate was enhanced. By using the double-layer structure, almost a 72-fold enhancement in the sensitivity coefficient was achieved compared to the monolayer structure. Additionally, the thickness of the SiO2 layer was also reduced with the application of the gold layer, resulting in easier device fabrication. This study allows for the possibility of designing and realizing robust Love wave sensors with high sensitivity and a low limit of detection.
Highlights
Surface acoustic wave (SAW) devices have been used in various sensing applications such as temperature [1], stress [2], gas [3], chemical and biological sensing [4] fields
The sensitivity coefficients of the monolayer and double-layer structures can be calculated via the energy variation in the substrate
Comparing the monolayer and double-layer Love wave sensors, the optimal thickness condition of the SiO2 layer is decreased by the added Au layer
Summary
Surface acoustic wave (SAW) devices have been used in various sensing applications such as temperature [1], stress [2], gas [3], chemical and biological sensing [4] fields. SAW sensors can be utilized to detect biomarkers which can be captured by the modified surface Owing to their high sensitivity, low cost, ease of integration with electronic circuits and possibility of real-time monitoring, SAW biosensors have been widely used for the bio-detection of proteins, DNA and cells [6,7,8]. The Love wave sensor, named the guided SH-SAW sensor, is a favored device for liquid phase applications [12,13,14] This device has a low velocity waveguide layer on the substrate. Compared with SiO2 , Au has a much lower velocity and the potential to be used as the second waveguide layer of Love wave sensors It shows stable physicochemical properties and biocompatibility for biomolecule self-assembly [25]. The Love wave velocity and energy distributions are calculated and the optimal thicknesses of waveguide layers are obtained
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