High frequency characterization of leaky waves for liquid delay line sensors

Surface Acoustic Wave (SAW) liquid sensors are being aggressively pursued, especially for biological point of care small systems. Shear Horizontal SAW (SHSAW) or leaky SAW (LSAW) are optimum in that they have reasonable loss in liquid, with most of the wave particle motion is in the horizontal plane. There has been previous work on SH- and L-SAW, but the physical parameters are often only reported at low frequencies. As the operational frequency is increased to >500 MHz, the wave trapping and losses are different than reported at low frequencies, and are a function of the propagation path overlays. Experimental results at higher frequencies for use in liquid sensor applications of these SAW modes using free, metallized, and grating paths will be presented.