Figure 5: Nanomechanical properties of the spike cuticle measured by
depth sensing nanoindentation. (A) Profile plots of indentation modulus
and hardness from the exterior to the interior of the cuticle on a
transverse cross-section (the nanoindentation grid is visible on the
light micrograph). A drop in local mechanical properties within the
outer helicoidal region (OHR) is evident. (B-C) Spatial variation of
indentation modulus, E, measured with higher lateral resolution from the
highly mineralized to the striated region, considering both (B)
transverse and (C) longitudinal cross-sections. (D-E) High resolution
maps of indentation modulus focusing on the transition between HMR and
STR on (D) transverse and (E) longitudinal cross-sections. Probed areas
are highlighted in squares on the light micrographs and lines indicate
the position of the mechanical profiles shown in B and C. HMR: highly
mineralized region; IHR: inner helicoidal region OHR: outer helicoidal
region; STR: striated region and TR: transition region. |