Investigation into massloading sensitivity of typical resonant structures attached to SAW Sensors

Recently there is greater interest in employing high aspect ratio resonant structures such as nano-pillars as sensing medium in SAW Sensors. In this work we have performed finite element method (FEM) simulation of a SAW device attached with typical resonant nano-pillars and studied the resonance frequency shift sensitivity caused by change in the Young´s modulus (E) and density (ρ) of the pillars. It is observed that the resonance frequency shift depends on the combined loading effect of E and ρ of the pillars. For an increase in E of the pillars, elastic loading dominates over inertial loading caused by ρ, accordingly an increase in resonance frequency of the SAW device is observed and vice versa. The results also show that nano-pillars made of hard polymers such as SU-8 show higher sensitivity for change in E or ρ.