FIGURE 2.

Schematic of typical indentation curves obtained using nanoindentation on an elastic-plastic sample. The slope of the initial unloading curve S = dF/dh is related to the reduced modulus according to Eq. 3. (a) Indentation without attractive interfacial forces. (b) Interfacial forces altering the shape of the curves; the intersection point between the horizontal (nondeflected cantilever) and the slope (deflected cantilever) is defined as the contact point. The indentation is the difference in the contact point positions (measured in vertical AFM piezo displacement) between loading a stiff sample (reference) and loading the fibril.