基于牙釉质微观结构的仿生材料制备

Natural structural materials are increasingly recognized as a potent source of inspiration for advanced engineering materials. Tooth enamel is an excellent example of a natural material that achieves simultaneous resistance to wear and fracture. These properties are generally mutually exclusive in engineering materials. The secret to the performance of most natural materials is their hierarchical microstructure. However, tooth enamel achieves its incredible performance from the decussation pattern of the enamel rods, which bestow its ability to divert and arrest cracks into regions of less threat. Preliminary investigations show that the complexity of the decussation patterns in mammals is scaled with the magnitude of bite forces. In particular, the microstructure of enamel from the hyena and sea otter teeth exhibits a "zig-zag" decussation pattern that apparently enables these mammals to crush bone and hard mollusks without fracture over the animal’s life. The decussation patterns have been optimized by Nature over thousands of years of evolution and could inspire the next generation of advanced engineering materials. .The proposed investigation will evaluate the microstructure and decussation patterns of tooth enamel, and use that knowledge to develop first generation engineered materials using additive manufacturing. Specifically, the three-dimensional decussation patterns of the enamel will be characterized for the molars of human, spotted hyena and sea otter teeth. The mechanical behavior of the enamel will be evaluated in terms of the decussation pattern design, and its resistance to crack growth under monotonic and cyclic loading. Three dimensional solid models of the enamel microstructures will be developed and used to produce compatible engineered material systems using additive manufacturing approaches that incorporate ceramics, composites and metals. The mechanical behavior of these bio-inspired materials will be evaluated in terms of their resistance to fatigue crack growth and fracture. The participating mechanisms to the crack growth resistance will be compared with those in the biological system and the key microstructural parameters of the decussation pattern geometry (e.g. rod bias angle, rod packing density, decussation wavelength, etc.) will be distinguished, which will enable further optimization. Results of this investigation will develop fundamental scientific knowledge that will potentially transform the field of advanced structural materials by identifying microstructures and methods of manufacturing that lead to the development of the next generation of advanced structural materials for a variety of applications.

天然生物硬组织材料具备独特的多层结构，不仅具备很高的强度和耐磨性，同时具备很高的韧性，它为先进材料设计提供了新的创新源泉。牙釉质具有独特的绞釉结构，能有效阻止内部裂纹扩展，哺乳动物牙釉质绞釉结构与其咬合力有直接的关系。本项目旨在探究牙釉质交叉绞釉结构形态，研究其增韧机制，结合增材制造技术制备新型仿生材料。具体研究内容包括：首先选取人、鬣狗和海狸等三种牙釉质作为研究对象，通过显微观察微观结构和绞釉形态；通过断裂力学测试方法评价这三种牙釉质的力学性能，分析绞釉形态几何参数与力学性能之间的关系；基于天然牙釉质的微观形态，利用常规陶瓷、金属和高分子材料，结合数值模拟和增材制造技术设计并制备具有特殊绞釉结构的新型仿生材料；利用断裂力学测试方法评价新型材料的力学行为，分析绞釉几何参数与材料力学行为的关系，并进一步优化仿生材料的设计。通过研究生物材料微结构与力学行为的关系，探索仿生材料设计与制备新方法。

生物材料拥有很高的强度和韧度，仿照生物组织材料的微观结构开展仿生材料设计与制备，为我们开发新型材料提供了一条可行的新途径。本项目旨在构建一种新的仿生材料设计理念，即基于牙釉质绞釉的增韧机制的仿生材料。采用高倍电子扫描显微镜SEM和透射电镜TEM观察多种生物材料，包括牙釉质绞釉、真皮盔甲和鱼鳞的微观形态，分析其材料成分，采用特定的几何形态特征参数定量描述生物材料的微观形态。通过数值建模分析，系统研究绞釉的几何形态、微观结构对牙釉质增韧效果的影响，揭示Parazone和Diazone对牙釉质裂纹生长的作用。通过模拟牙釉质绞釉的微观结构，揭示了牙釉质曾韧机制。结合目前最新的增材制造技术，制备高硬度、高韧度新型材料。具体研究内容包括：通过观察几种不同牙釉质绞釉微观结构形式，确定绞釉形态关键几何参数；通过数值模拟和力学实验，建立绞釉微观结构参数与材料力学行为之间的关系；开展新型材料微结构的设计，并采用增材制造技术，使用陶瓷三维打印机制备具有三维交织微柱结构的多种仿生材料，开发出了具有高强度、高韧度的仿生材料，并通过力学测试验证设计参数与材料断裂韧度的一致性。

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