Theoretical and experimental verification on mass sensitivity of surface acoustic wave biosensor

The evaluation and improvement on the performance of the Surface Acoustic Wave Biosensor(SAWB)has attracted great attention.In this paper,a SAWB is designed and fabricated for detecting the specific binding of antibody to antigen.A real-time characterization method is proposed for test of the load sensitivity of this SAWB.In the first stage of the study,a three-dimensional finite element analysis model of the Love wave sensor on the SiO₂ waveguide layer with quartz piezoelectric substrate was established based on the two-dimensional approximation hypothesis and periodic boundary conditions.Influence of the waveguide layer on the sensitivity of the Love wave sensor was theoretically verified as well.Further,the surface acoustic wave sensor on ST-90°X quartz substrate was prepared by MEMS process and SiO₂ waveguide layers of different thickness allowed to grown on the substrate surface by magnetron sputtering coating technology.Using thermal evaporation technology,thin layer of aluminum film was coated on the delay line area and further the thin film was corroded off using TMAH from the substrate under the real-time monitoring of SAWB.Influence of thickness of SiO₂ thin film on the sensitivity of SAWB was studied in detail and the optimum thickness for better sensitivity was find out.