Modal Actuation and Sensing With an Active AFM Cantilever

Modal actuation and sensing are implemented on a microfabricated AFM cantilever with a two-layer piezoelectric stack transducer. The top transducer is shaped as the second derivative of the first mode shape. The bottom transducer is uniformly distributed along the cantilever length. The purpose of this work is to demonstrate that modal actuation and sensing can be used to eliminate other resonances from frequency response function of the active cantilever, except the first mode. First-order mathematical formulations are presented to model transverse vibrations of the cantilevers under this study. Microfabrication steps and characterization of these cantilevers are reported. Their respective actuation and sensing gains are determined for comparison with conventional active cantilevers. Electromechanical coupling coefficients are also calculated to exhibit reciprocity of modal actuation and sensing in eliminating higher modes from the frequency response. The advantages of modal actuation and sensing in avoiding instabilities in feedback controlled AFM active cantilevers are also demonstrated.