Vibration modeling of AFM micro cantilever by considering the axial load in the air and ‎liquid workspaces

5/23/2019 12:00:00 AM

This thesis is devoted to the vibrational modeling of the micro cantilever of the atomic force microscope with piezoelectric layers in noncontact work mode taking into account the axial load in air and liquid environments. The atomic force microscope has provided researchers with access to the nano world. This tool is used as a powerful tool for taking pictures of surfaces, moving particles, and measuring bits of force. As dynamic parameters of the AFM nano robot, parameters such as amplitude, frequency, and phase of motion are used as feedback factor in the control system in extracting sample surface information and nanoparticle voltage, the vibrational analysis of the nano robot micro cantilever in order to extract these parameters is inevitable. Also, the high utilization of slope micro cantilever is highly dependent on the need to apply axial and transverse forces in the model. In order to simulate the microscope of the atomic force microscope, this device should be considered. In non-contact mode, the vibrational micro cantilever gradually approaches the surface of the specimen, and due to the forces entering the micro cantilever from the sample surface and the environment, the frequency of amplification and oscillation amplitude change. In this regard, the theory of Timoshenko beam and the modified coupling stress theory are considered with consideration of axial displacement in four-layer piezoelectric microscope modeling. The energy method is used to derive systems equations and the finite element method is used to discriminate the equations. The frequency and time responses of the system are compared with experimental results and simulations of other researchers. Also, to observe differences in the type of micro cantilever, frequency and time responses are calculated and compared for three AFM microencapsulated geometries. Also, the effects of the work environment change on the vibrational behavior have been investigated and it has been shown that with increasing concentration of the environment, the frequency of the system intensification as well as the micro cantilever vibration amplitude decreases. In the next step, the topography of the surface of the sample for rectangular and curved roughnesses was investigated and evaluated for stimulation at two first resonance frequencies and it was shown that the delay time in the second stimulation decreases. Also, the time delay in the liquid environment is less than the air environment. In the ambient air, the stimulation with a second frequency actuation the shape of the ripple better than the first frequency stimulation, but in the fluid environment, this is not always the case, and due to the frequency difference between the excitement of the fluid medium and the frequency of excitation, the presence of disturbances and noise to the micro cantilever The form of roughness in the first and second stimulation can be better or the worse. Keywords: vibration, microcantilever, pizoelectric, AFM, Timoshenko beam, axial load