Elastic surface properties studied using scanning force microscopy

Scanning force microscopy (SFM) was used to measure the local elastic properties of the substrate at nN level. Well defined experimental conditions were assured by performing measurements in a liquid environment, using a 'liquid cell' setup. The information about elasticity was obtained from the dependence of loading force versus distance between probing tip and sample. The indentation, measured as a difference between curves for stiff, reference sample and studied samples was used to determine the local Young's module. In the determination it was assumed that the tip shape is spherical and tip-sample interaction is described by the Hertzian theory. Different surfaces such as glass, 300 nm thick layer of the polystyrene, adhesive gel or even the very soft biological material as the cell membrane were measured.