High sensitive I-shaped piezoelectric excited millimeter-sized cantilevers as mass and liquid level detectors

Abstract

In recent years, there have been great interests in enhancing the sensitivity of resonating piezoelectric-excited millimeter-sized cantilever (PEMC) sensors. Operating principle of these sensors is based on measuring the electrical impedance of piezoelectric layer attached to the base cantilever. While most of studies in this area have focused on sensitivity improvement by minimizing the dimensions of the base cantilever, in this paper effect of modifying the cross-section shape of cantilever on enhancing the detection sensitivity of these sensors has been studied. To this end, a new PEMC sensor with I-shaped cross-section was proposed. Finite element method (FEM) was used to explore the sensitivity of proposed I-shaped cross-section PEMC sensor and also the PEMC sensor with the same dimensions but rectangular-shaped cross-section. Performances of these sensors were studied in two separate applications, including mass sensing while point masses were loaded on the cantilever surface at it's free end and also liquid level detecting whereas the PEMC sensors were partially inserted in water. To validate the simulation results achieved by FEM, sensors were fabricated and tested via an experimental setup. Simulation results were in a good agreement with experimental outcomes to the extent that the deviations observed between first-order resonance frequencies achieved by these two methods were less than 5 percent in all cases. Experimental outcomes show that proposed I-shaped cross-section PEMC sensor is more sensitive than rectangular-shaped cross-section sensor with the same dimensions. In mass sensing and liquid level detecting applications, the sensitivity of proposed I-shaped sensor was 1.5 to 2.04 times and 1.38 to 3.75 times more than the rectangular-shaped PEMC sensor, respectively.