Atomic Force Microscope Nanoindentations to Reliably Measure the Young’s Modulus of Soft Matter

The analysis of nanomechanical properties is becoming an increasingly useful tool in a large variety of fields, ranging from biology to polymer science. The Atomic Force Microscope, AFM, can bridge the information about morphology, obtained with outstanding resolution, to local mechanical properties. When performing an AFM nanoindentation, the rough force curve, i.e. the plot of voltage output from the photodiode vs. the voltage applied to the piezoscanner, can be translated into a curve of the applied load vs. penetration depth after a series of preliminary determinations and calibrations. The Young’s modulus of the sample can be finally extracted from the force curve, through a correct application of contact mechanics models. All the calibrations needed are thoroughly described in this work, together with the details about contact mechanics, in order to clarify the correct procedure needed for the analysis of nanomechanical properties through AFM nanoindentations.