Spatial resolution and property contrast in local mechanical mapping of polymer blends using AFM dynamic force spectroscopy

Bahrami, Amir [UCL] Bailly, Christian [UCL] Nysten, Bernard [UCL]

The spatial resolution and the contrast in mechanical property mapping by atomic force microscopy (AFM)modes based on dynamic force-curve acquisition, HarmoniX™(HMX) and Peak-Force-Tapping-QNM™(PFT-QNM)modes, are discussed in terms of contact radius, probe type and imaging parameters. The study is based on model polymer samples including elastomers, thermoplastics and thermoset resins and on contact mechanics considerations to provide a better understanding of the main parameters governing spatial resolution and property contrast in AFM-based nanomechanical mapping. The tip-sample interaction area and volume characterized by the contact radius are the key parameters governing the spatial resolution in adhesion force and elastic modulus images, respectively. The contrast in mechanical properties depends on the proper choice of the probe and on the control of the pixel size and the imaging force. The study also demonstrates that all these parameters are mutually interconnected and may have contradictory influences.