Multi-scale design of the structure and mechanical performance of the deep-sea hydrothermal mussel (Bathymodiolus aduloides) shell.

Deep-sea hydrothermal vents are renowned for being among the most extreme environments on Earth. However, the mussel shells found in these vent sites demonstrate remarkable productivity, despite being subjected to high pressure as well as unusual levels of heavy metals, pH, temperature, CO2, and sulphides. To comprehend how these mussels endure such extreme conditions, a systematic comparative study was conducted, focusing on the unique chemical composition, structural designs, and mechanical properties of hydrothermal vent mussels (Bathymodiolus aduloides) in comparison to shallow-water mussels (Mytilus edulis). The results revealed that the shell of B. aduloides exhibited a multilayered structure and a higher curved cross section compared to M. edulis. The cross section primarily consisted of a thicker periostracum layer and a highly mineralized calcium carbonate layer, exhibiting distinct changes in chemical composition and microstructures. Furthermore, the shell of B. aduloides demonstrated higher modulus and toughness, as well as lower density and hardness, when compared to the shell of M. edulis. Various toughening mechanisms of B. aduloides were observed on broken surfaces, including crack deflection, mineral bridges, and nano-particles. The chemical composition and multiscale design strategy of the B. aduloides shell, as revealed in this study, are expected to provide valuable insights for the development of novel bioinspired materials suitable for extremely high-pressure environments, such as deep-sea submersibles and mining equipment.