Hierarchical architecture and mechanical optimization of monetaria annulus shell: insights for bioinspired material design
摘要
Natural mollusk shells achieve exceptional combinations of hardness and toughness through hierarchically organized architectures. While the structural–mechanical relationships of many nacreous bivalves and conch shells have been studied, the shell of Monetaria annulus remains largely unexplored. Here, we investigate the hierarchical structure, composition, and mechanical performance of Monetaria annulus using an integrated multi-scale characterization approach. The shell exhibits a pronounced mineralization gradient, with outer layers more highly mineralized than inner layers in some regions, and comprises five structurally distinct regions, including stacked and tiled crossed-lamellar layers and an interlocking inner architecture. The fundamental building block of the shell is crystalline aragonite fibers, and the weight fraction of organic substance is ∼2.62%. The distinct crystal orientation of stacked and tiled layers could be clearly distinguished from confocal Raman mapping analysis. While the stacked layers and tiled layers exhibit nearly identical hardness and elastic modulus, tiled layers promote crack branching and microcrack formation. These findings demonstrate that Monetaria annulus achieves damage tolerance through the synergistic integration of mineralization gradients, layer orientation diversity, and nanoscale fiber alignment, offering valuable principles for the design of lightweight, impact-resistant bioinspired materials.
