FIGURE 5.

Imprints on two similar collagen fibrils with the same individual tip. To eliminate a tip-shape influence on the imprint shape, the fibrils are arranged perpendicular to each other but the tip orientation with respect to the substrate is unchanged. The nonuniform shape of the imprints indicates different material properties in longitudinal and transversal directions. Pileup (arrow) appeared due to the high-load indentations (2 μN). Imprint depth (from left to right): 28 ± 1 nm; 20 ± 1 nm; 28 ± 1 nm; and 29 ± 1 nm.