Abstract
The cuttlebone is a rigid buoyancy control device which enables the cuttlefish to maintain a fixed position in water with minimal effort. It must be strong enough to withstand hydrostatic pressure and lightweight in order not to sacrifice buoyancy. In this study, structure and mechanical properties of cuttlebone obtained from Sepia pharaonis were investigated. Micro-structural features of cuttlebone were characterized by stereoscope, micro-CT, and SEM. The cuttlebone, mainly made of CaCO3 in aragonite form and chitin, had a unique cellular architecture. Parallel lamellae called septum and supporting walls named pillars formed chambers with spacing varying from 200 to 400 μm. Numerous thin organic sheets between pillars within a chamber were observed. Mechanical properties were evaluated by compression tests on dry, rehydrated and fresh samples in three loading directions – parallel, perpendicular, and 45 degree to the septums. Results showed septums exhibit superior mechanical properties orientations compared with pillars. Deformed samples were examined by micro-CT and SEM at progressive stages and deformation mechanisms were evaluated. The role of mineral and organic component of cuttlebone played in the mechanical property was evaluated by deproteinization and demineralization. The results showed strong synergistic effect between the two constituents in the strength of cuttlebone. This investigation could further lead to the design of novel bio-inspired composites and biomedical applications.