Mass-change sensitivity of piezoelectric-excited millimeter-sized cantilever (PEMC) sensors: Model and experiments

We show for the first time that approximate analytical models do not predict mass-change sensitivity of cantilever sensors of non-uniform cross-section. On the other hand, finite element model (FEM) is a better approach for determining the performance of such sensors. Specifically, FEM of piezoelectric excited millimeter-sized cantilever sensors (PEMC) give sensitivity values that are in reasonable agreement with experimentally determined values of 20 pg/Hz, reported earlier. The approximate analytical model predicts resonance frequency of PEMC within 10% error, but it under predicts mass-change sensitivity by three orders of magnitude. FEM analysis of first and second resonance mode frequencies of a sample of ten PEMC sensors of various geometries were found to compare favorably (∼2–4%) with experimental values. Mass sensitivity determined using FEM is within a factor of three of experimental values. Through simulations we discover two important properties of the PEMC sensors: (1) The sensitivity is a strong function of attached mass. Specifically, sensitivity is the highest at low attached mass. (2) PEMC sensors become less sensitive with increasing attached mass, which results in sensors that exhibit wide dynamic range of six logs.