Sensing Mechanisms Mass Loading Film/Liquid Visco-elastic Changes Film/Liquid Conductivity Changes Stress or Strain Temperature Pressure Applications Biomedical Sensing Chemical Gas/Liquid Sensing Fluid/Film Conductivity Sensing Viscosity Sensing Temperature Sensing Pressure Sensing Torque Sensing Humidity Sensing

The shear horizontal acoustic plate mode (SH-APM) device combines the best properties of both the BAW and SAW devices.  It employs separate input and output transducers in order to allow differential signal measurements like the SAW structures but also allows the sensor crystal to be employed as a physical barrier between the electronics and the sensing medium.

The wave is a waveguide mode with energy throughout the bulk of the crystal and is dependent on the thickness of the substrate.  Like all the previous surface launched acoustic wave devices, the SH-APM device uses input and output IDTs to launch and receive the acoustic wave.  Similar to the BAW thickness shear mode device, the maximum displacements occur on the top and bottom surfaces of the plate.  Similar to the STW and Love Mode devices, the surface displacement is shear and in the plane of the plate so it can be used for liquid-based applications. The waveguide modes have energy distributed between the two surfaces as a standing wave as in the BAW sensor but traveling along the surface as in a SAW.  The continuous exchange of energy between the two surfaces allows the signal between the IDTs to be influenced by changes on the opposite surface.