Laser vibrometry and impedance characterization of piezoelectric microcantilevers

Abstract

This paper gives a precise insight into the frequency response of self-actuating cantilevers, extended to high-order modes. An original approach is presented, based on a mixed experimental scheme regarding both impedance and laser Doppler interferometry measurements, performed with an impedance analyser and a vibrometer, respectively, and supported by some computational analysis as well. The experimental results obtained by the two different techniques agree reasonably well, as for the location of the resonances in the spectrum is concerned. However, certain particular modes, torsionally shaped and detected by the vibrometer, show no impedance change due to symmetry reasons. A computational model has been successfully employed and utilized to shed some light on this phenomenon. The model demonstrates that the induced reaction charge redistribution cancels out only for those particular torsional modes featuring an anti-symmetrical nature; as a consequence, no impedance change is to be expected in the resonances. This explanation perfectly fits the impedance measurements carried out, including the missing torsional modes.