Electrode optimization for a lateral field excited acoustic wave sensor

Lateral field excited (LFE) acoustic wave sensors have a distinct advantage over the standard, AT-cut, quartz crystal microbalance (QCM) in which the thickness shear mode (TSM) is excited by electrodes on the sensing and reference surfaces. The TSM in LFE sensors is excited by placing electrodes only on the reference surface of the crystal, leaving the sensing surface free. Due to the lack of a shielding electrode on the sensing surface, the TSM electric field is able to penetrate into an analyte selective film or an adjacent liquid thus enabling the detection of mechanical and electrical property changes in the film or liquid. Several electrode designs on the reference surface are examined and evaluated by measuring each sensor's admittance and resonant frequency when exposed to a variety of analytes and liquids. These results are compared to the results obtained using a standard QCM.