CAREER: Biomineralized architected metamaterials: structural design and formation mechanisms

摘要（非技术）与地质矿物相比，生物矿物是由生物体形成的矿物结构。贝壳、我们的牙齿和骨头都是生物矿物的好例子。虽然我们经常对地质矿物的各种特定晶体几何形状感到惊讶，但生物矿物通常以其任意但通常复杂的三维（3D）形态为特征。此外，许多生物矿物结构的内部微观结构也非常复杂，并在3D中精心组织。这种层次结构的复杂性导致生物矿化结构的显着的机械强度和耐久性，尽管事实上，矿物本身是脆性的。目前，我们在解释生物矿物复杂的三维微观结构和形态是如何出现和调控方面的知识有限。该奖项通过使用海星中的生物矿化骨骼作为模型系统，旨在表征其复杂的3D微观结构以及潜在的形成机制。海星的骨骼由数百毫米大小的生物矿化元素组成，这些元素被称为小骨，嵌入其柔软的身体中。这种独特的骨骼设计使海星在运动过程中变得灵活，但在需要时也变得僵硬。听小骨的特征在于基于单晶方解石的晶格状多孔微观结构，这使得它们重量轻、坚固且耐损伤。从这项研究中获得的海星生物矿化机制的新知识将为我们提供一个更好的理解棘皮动物，甚至可能，其他无脊椎动物和脊椎动物生物矿化组织的三维结构进化过程。本研究中对海星生物矿化骨骼的多尺度结构，形成机制和力学性能的见解将为合成低密度材料的设计和制造提供重要的经验教训，从而使美国经济和社会受益。与产生生物矿化材料新知识的研究目标相一致，拟议的教育和推广计划将提高当地和全国STEM教育的质量。海星形成生物矿化的毫米大小的骨骼元素，称为小骨，用于保护，运动和其他目的。像其他棘皮动物的骨骼一样，这些听小骨由含镁方解石和少量嵌入矿物基质中的有机物质组成。有趣的是，尽管它们是单晶体，但听小骨的特征是它们复杂的双连续网络状微观结构，称为立体结构。这个提议的CAREER计划的目标是了解这些生物矿物的复杂形态是如何在3D中形成和控制的，以及这种结构控制如何影响它们的机械性能。我们仔细选择周期性的，格子状立体结构，称为生物矿化建筑超材料（BAM），从一个模型海星系统。PI将首先量化完全形成的BAM结构的多尺度3D形态，包括其3D晶格网络，表面曲率和矿物内有机材料的空间分布，然后通过新型断层扫描成像技术研究3D结构演化，矿物晶体学和矿物前体在形成听小骨的生长前沿的分布。最后，多尺度三维结构控制的机械效果将建立通过结合实验测试和计算建模。这项研究的主题是一个有吸引力的话题，为学生和更广泛的公众，拟议的教育和推广计划将整合材料科学，生物学和工程，以配合研究目标，更好地了解生物材料。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Abstract (non-technical)In contrast to geological minerals, biominerals are mineral-based structures formed by organisms. Seashells, our teeth and bone are good examples of biominerals. While we are often amazed by geological minerals’ various specific crystal geometries, biominerals are usually characterized by their arbitrary yet often complex three-dimensional (3D) morphologies. Moreover, the internal microscopic structures of many biomineral-based structures are also extremely intricate and carefully organized in 3D. This hierarchical structural complexity leads to biomineralized structures’ remarkable mechanical strength and durability, despite the fact that the minerals themselves are intrinsically brittle. Currently we have limited knowledge in explaining how biominerals’ complex 3D microstructures and morphologies are emerged and regulated. This award, by using the biomineralized skeleton in a starfish as a model system, aims to characterize its complex 3D microstructure as well as the underlying formation mechanisms. The skeleton of starfish consists of hundreds of millimeter-sized biomineralized elements, known as ossicles, which are embedded within its soft body. This unique skeletal design allows the starfish to be flexible during locomotion but also to become stiff when required. The ossicles are characterized by their lattice-like porous microstructure based on the single-crystalline calcite, which makes them lightweight, strong, and damage tolerant. The new knowledge gained from this study on the biomineralization mechanisms in starfish will provide us a better understanding of the 3D structural evolution processes for echinoderms, or possibly, even other invertebrate and vertebrate biomineralized tissues. The insights on the multiscale structure, formation mechanisms and mechanical properties obtained in this study for starfish’ biomineralized skeletons will provide important lessons for the design and fabrication of synthetic low-density materials and thus benefit the U.S. economy and society. Aligned with the research goal in generating new knowledge of biomineralized materials, the proposed education and outreach programs will improve the quality of STEM education both locally and national-wide. Abstract (technical)Starfish form biomineralized millimeter-sized skeletal elements, known as ossicles, for protection, locomotion and other purposes. Like other echinoderms’ skeletons, these ossicles consist of magnesium-bearing calcite with a small amount of organic materials embedded in the mineral matrix. Intriguingly, despite their single-crystal nature, ossicles are characterized by their complex bicontinuous network-like microstructure, known as stereom. The goal of this proposed CAREER program is to understand how these biominerals’ complex morphology is formed and controlled in 3D and how such structural control impacts their mechanical performance. We carefully select the periodic, lattice-like stereom structure, termed as biomineralized architected metamaterial (BAM), from a model starfish system. The PI will first quantify the multiscale 3D morphology of the fully formed BAM structure in terms of its 3D lattice network, surface curvature, and spatial distribution of organic materials within minerals and then investigate the 3D structural evolution, mineral crystallography, and distribution of mineral precursors at the growth front of forming ossicles through novel tomography imaging techniques. Finally, the mechanical effects of multiscale 3D structural control will be established via combined experimental testing and computational modeling. The subject of this study is an attractive topic for students and the broader public, and the proposed education and outreach programs will integrate material science, biology, and engineering to align with the research goal in better understanding biological materialsThis award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.