Finite element simulation of Love wave sensor for the detection of volatile organic gases

Abstract

The three-dimensional (3D) finite element (FE) simulation and analysis of Love wave sensors based on polyisobutylene (PIB) layers/SiO2/ST-90°X quartz structure are presented in this paper, as well as the investigation of coupled resonance effect on the acoustic properties of the devices. The mass sensitivity of the basic Love wave device with SiO2 guiding layers is solved analytically. And the highest mass sensitivity of 128 m2/kg is obtained as h s/λ = 0.175. The sensitivity of the Love wave sensors for sensing volatile organic compounds (VOCs) is greatly improved due to the presence of coupled resonance induced by the PIB nanorods on the device surface. The frequency shifts of the sensor corresponding to CH2Cl2, CHCl3, CCl4, C2Cl4, CH3Cl and C2HCl3 with the concentration of 100 ppm are 1.431 kHz, 5.507 kHz, 13.437 kHz, 85.948 kHz, 0.127 kHz and 17.879 kHz, respectively. The viscoelasticity influence of the sensitive material on the characteristics of SAW sensors is also studied. By taking account of the viscoelasticity of the PIB layers, the sensitivities of the SAW sensors with the PIB film and PIB nanorods decay in different degree. The gas sensing property of the Love wave sensor with PIB nanorods is superior to that of the PIB films. Meanwhile, the Love wave sensors with PIB sensitive layers show good selectivity to C2Cl4, making it an ideal selection for gas sensing applications.