A computational study on detection of ultra small volumes of liquid and solid media in microcavities using surface acoustic wave device

In this study, we use finite element method (FEM) analysis to investigate a surface acoustic wave (SAW) based system. This platform involves a regular SAW device with two interdigitated transducers (IDTs) as input and outputs along with a microcavity etched in the middle of the delay line for sensing. This sensing part of the system houses liquids and solid microbeads for the purposes of our simulations. With a peak frequency of 200 MHz, the system mechanically analyzes sample volumes less than 10 pL through coupling of Rayleigh waves to the captured samples. In mixture of glycerin and water between 40% and 90% an approximately linear relation exists between the output phase and glycerin percentage. At this range, a maximum change in the phase of -0.77° was obtained per glycerin percent for microcavities with a depth of 8 μm. When microbeads with a stiffness of 3 GPa are placed in a liquid mixture of 10% glycerin, a linearized sensitivity of -69.4 °/GPa around 3 GPa point is obtained.