Metrological characterization of low stiffness AFM cantilevers for biological applications

This thesis work is based on conducting experimental activities to measure the resonance frequency and the quality factor of different cantilevers used in Atomic Force Microscopy (AFM), using the micro Laser Doppler Vibrometer and the Scanning Electron Microscope (SEM) available at INRiM. The aim of this thesis is therefore to investigate the experimental parameters involved in the use of Sader's formula to calculate the spring constant of cantilevers in AFM, together with a detailed uncertainty analysis. Although a procedure exists to ensure metrological traceability to SI units for nanoscale displacements in the horizontal X and Y axes and in the vertical Z axis, a method to ensure traceability for nanoscale forces has not yet been developed. Due to the difficulty in directly providing force traceability at the micro and nanoscale level, an indirect method is employed that allows calculating nano-force values ​​from the spring constant of the cantilever. This analysis was performed on different types of cantilevers, with different geometries and resonance frequencies, all with a rather low stiffness compared to other types of cantilevers available on the market since the ones that were chosen for the analysis are employed in biomedical applications. To ensure a thorough evaluation, a cantilever with a higher stiffness, typically used for mechanical applications, was also analyzed to verify the accuracy of the method even in different initial conditions and extend its effectiveness to any AFM application.