Highly Sensitive SH-SAW Resonator with SiO2 trenches for Biosensing Application

Abstract

The paper presents three dimensional finite element simulation of a sensitive shear-horizontal surface acoustic wave device for biosensing application. The resonator consisting of 36°-YX LiTaO3 substrate with SiO2 trenches generates a shear-horizontal standing wave. Eigenmode study and frequency response are used to calculate displacements, admittance and electromechanical coupling coefficient of the device. For a given mode, the coupling coefficient of the device increases with trench height to a maximum of about 7% and then starts to decrease till next higher order mode becomes dominant. The trenches not only serve as guiding layer to keep the energy of the wave at the surface but also cause coupled resonance leading to increase in resonance frequency and average stress at the contact area between trench and substrate. Mass loading of resonator is simulated by applying the equivalent surface mass density of double stranded DNA of length 50 base pairs uniformly over the surface area of trenches. Close to the resonant height of trenches, mass loading causes a large frequency shift making the device a highly sensitive biosensing platform.