Implications of a Low Stiffness Substrate in Flexural Plate Wave Sensing Applications

Kirchhoff plate equations are examined for flexural plate wave sensors with a polymeric substrate that is mechanically similar to the polymer sensing layers commonly used in mass loading and gas sensing applications. The new analytical derivations for sensitivity are examined both experimentally and through finite element analysis (FEA). For substrates with a large in-plane stress, the behavior of the sensor is consistent with other gravimetric sensors based on flexural plate waves. In the case of low stress, the influence of variations in substrate stiffness and stress significantly outweigh the effects of mass loading in sensor frequency response. Experimental results using a poly(vinyl alcohol) sensing layer and poly(vinylidene fluoride) substrate are compared with analytical and FEA models, and demonstrate good adherence. The FEA models are also used to illustrate the relevant influences of mass loading, variations in substrate stiffness, and stress on the sensor response.