Unravelling the Twist in Narwhal Tusk with Hierarchical X-Ray Scattering Tensor Tomography

Narwhals are mysterious animals whose tusk has a unique spiral structure with highly anisotropic mechanical properties. We hypothesize that the orientation of the nanostructure reflects the spiral macrostructure, defining its mechanical properties. Previous experiments have shown microstructure with a high anisotropy in the tusk direction with helical deviations from the tusk axis, however, the small sample size restricted the ability to connect the macrostructure to the local features investigated. How the organization of the nanostructure connects to these macroscopic features can only be done by probing the nanostructure through scattering in macroscopic samples. Therefore, we propose to use small- and wide-angle X-ray scattering tensor tomography with a high-energy beam to study the 3D arrangement of the mineralised collagen fibres in the tusk at the macroscopic scale. That will be of high importance for understanding the structure of the tusk and its connection to tusk mechanics.独角鲸（Narwhal）是一种神秘的海洋生物，其獠牙拥有独特的螺旋结构，且具备高度各向异性（anisotropic）的力学特性。本研究假设，纳米结构的取向与螺旋宏观结构存在对应关系，并由此决定了獠牙的力学特性。此前的实验已观测到，獠牙方向存在高度各向异性的微观结构，且该结构与獠牙轴线存在螺旋偏移；但由于样本量过小，无法将宏观结构与所研究的局部特征建立关联。唯有通过对宏观样本开展散射探测以解析纳米结构的排布方式，才能明确纳米结构的组织形式与这些宏观特征之间的关联。因此，本研究拟采用配备高能束流的小角度与宽角度X射线散射张量断层扫描（small- and wide-angle X-ray scattering tensor tomography）技术，在宏观尺度下解析獠牙内矿化胶原纤维（mineralised collagen fibres）的三维排布结构。该研究对于阐明独角鲸獠牙的结构特征及其与力学特性的关联具有重要意义。