Influence of Hydration on the Micromechanical Properties of Silica Spicules from the Venus Flower Basket (Euplectella Aspergillum)

Abstract

The spicules of the deep-sea sponge Euplectella aspergillum show exceptional mechanical properties due to their unique layered structure. In the present study, a systematic study utilizing in situ nanoindentation was conducted to understand the influence of water on the micromechanical properties of these spicules. The properties of the spicules were investigated in three conditions—dry state, after 24 h of exposure, and after 1 week of exposure with water. To isolate the effect of the architecture of the spicule, properties of the central core and layered regions of the spicule were probed separately. The results of nanoindentation revealed that the layered regions were significantly softer and more compliant than the central core of the spicule. The properties of the central core remained unchanged when exposed to water. On the other hand, layered regions showed a decrease in their stiffness and hardness. These effects were attributed to the hydrated nature of silica and plasticization of the organic interlayers, respectively. The present results provide insight into the role of the architecture of the spicule and its organic-inorganic constituents in determining its mechanical behavior in water environment.