A study of Love wave sensors with SU-8 guiding layers

Love wave sensors employing guiding layer deposited on a ST-90degX quartz were presented and analyzed. Since solidified SU-8, as one kind of polymer, has low shear velocity, while its rigidness is almost same with SiO₂, So SU-8 is very appreciated for Love wave sensor layer. Firstly, as for the two layers structure (SU-8/ ST90degX -quartz), the Love wave phase velocity was calculated by propagation equation and boundary conditions, and mass sensitivity is then deduced by perturbation theory. A relative larger mass sensitivity than SiO₂ is obtained when an optimal relative thickness is adopted. Corresponding experimental study of Love wave devices with SU-8 film as guiding layer has been performed. A device operating at a fundamental frequency of 125 MHz is fabricated. The experimental results give comparing results with theoretical results.