NPL required a parametric model of the AFM to be generated, which would allow the user of the macro to select the shape of the cantilever, followed by the calculation of natural frequencies and mode shapes using finite element analysis during the calibration procedure.
In order to accurately simulate the static and dynamic response of the cantilever the following properties had to be accounted for: radii of curvature, the level of residual stress in the coating, coating thickness and the mass of the tip.
created a parametric model using ANSYS where the AFM probe was modelled by means of 8- noded 3D elements with large strain large deflection capability. The top surface of the cantilever was then coated with 4 noded shell elements to simulate the 30-50 nm thick layer which coats the device. The effect of the AFM tip was modelled with an offset mass element.
A full model of the AFM was generated in order to capture any torsional or unsymmetrical modes.
The analysis work was carried out in two stages. The macro for the first stage was written to allow for the following options: |