EAGER/Collaborative Research: Understanding How Enamel Prism Lattices Promote a Remarkable Combination of Fracture and Wear Resistance in Grazing Mammal Dentitions

EAGER/合作研究：了解牙釉质棱镜晶格如何促进放牧哺乳动物牙列的抗折性和耐磨性的显着组合

• 批准号: 1937050
• 负责人: Gregory Erickson
• 金额: $ 6.65万
• 依托单位: Florida State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-08-01 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1937050&HistoricalAwards=false
• 关键词: EAGER; Collaborative; Research; Understanding; How

Fracture and wear are common issues in engineering - to the extent that the terms "worn," "fractured," and "broken" are generally synonymous with the end-of-utility of devices. In many cases, traditional materials fail to meet the complex, simultaneous performance requirements that would be ideal for next generation engineering systems. The enamel of the teeth of grazing animals represents one of nature's most remarkable biological materials -- a ceramic-like composite showing exceptional strength, toughness, wear-resistance, and ability to slow crack propagation. This is an important set of properties for a structure that is key to long-term survival in these animals - as functional teeth are required for feeding. This EArly-Concept Grant for Exploratory Research (EAGER) project will study these damage-tolerant biomaterials using a combination of evolutionary biology, biomechanics, and materials science. Results and methods from this research will be of considerable interest to investigators in many disciplines, including engineering, materials science, evolutionary biology, ecology, comparative anatomy, mammalogy, and paleontology. The research will also support the development of novel, sustainable materials with improved wear and fracture behavior. Graduate students will be involved in this truly interdisciplinary project and learn how the various fields can work together to tackle challenging questions. This research will also introduce a more effective, evolutionary approach for exploring nature for biomimetic examples.The goal of this interdisciplinary research is to specifically understand the biomechanical form, function and performance of enamel lattices, known as Modified Radial Enamel (MRE), in the grinding teeth of large herbivorous mammals. Samples will be obtained from numerous species, including equines (horses), bovids (e.g. bison and cattle) and suids (e.g. warthogs). This study will specifically focus on how these animals' teeth endure tens to hundreds of millions of high stress contact loading cycles and impacts while chewing tough and abrasive plant matter, such as grasses whose roots are laden with hard, fracture-promoting sediment inclusions. The underlying hypothesis is that MRE is an evolutionarily optimized compromise for: 1) incredible fracture resistance due to prism arrangements that localize damage and strategically control crack direction; 2) unexpected strength and toughness made possible by compliant proteinaceous prism sheaths that circumvent hydroxyapatite's inherent brittleness; and 3) wear resistance conveyed through hard, hyper-mineralized, oriented enamel prisms. The project will investigate this hypothesis through two objectives. First, the study will use an evolutionary biology approach to identify the ancestral enamel fabric character states to MRE that independently evolved in horses, bovids and warthogs. From this information, it will be possible to readily identify the specific evolutionary modifications to the enamel fabrics that enabled grinding and identify living species that can be used to undertake comparative biomechanical assessment. Second, the project will investigate the structure-property relationships of the enamel across multiple length scales by comprehensively characterizing the material properties using micro-and nano-mechanical tools, spectroscopy, and advanced electron microscopy. Teeth of grinding species with MRE will be compared with close relatives that retain the ancestral enamel fabrics, thereby revealing the salient anatomical changes that enabled the optimized combination of biomechanical properties.This 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.

断裂和磨损是工程中的常见问题——术语“磨损”、“断裂”和“损坏”通常与设备的使用寿命终止同义。在许多情况下，传统材料无法满足复杂、同步的性能要求，而这对于下一代工程系统来说是理想的选择。食草动物的牙釉质代表了自然界最卓越的生物材料之一——一种类似陶瓷的复合材料，具有卓越的强度、韧性、耐磨性和减缓裂纹扩展的能力。这是这些动物长期生存的关键结构的一组重要特性——因为进食需要功能性牙齿。 这个探索性研究早期概念资助 (EAGER) 项目将结合进化生物学、生物力学和材料科学来研究这些耐损伤生物材料。这项研究的结果和方法将引起许多学科的研究人员的极大兴趣，包括工程学、材料科学、进化生物学、生态学、比较解剖学、哺乳动物学和古生物学。该研究还将支持开发具有改善磨损和断裂行为的新型可持续材料。研究生将参与这个真正的跨学科项目，并了解各个领域如何共同努力解决具有挑战性的问题。 这项研究还将引入一种更有效的进化方法，用于探索自然的仿生实例。这项跨学科研究的目标是专门了解大型草食哺乳动物磨牙中牙釉质晶格（称为改良径向牙釉质（MRE））的生物力学形式、功能和性能。 样本将从许多物种中获取，包括马科动物（马）、牛科动物（例如野牛和牛）和猪科动物（例如疣猪）。这项研究将特别关注这些动物的牙齿在咀嚼坚韧和磨蚀性植物物质（例如根部充满坚硬、促进断裂的沉积物的草）时如何承受数千万至数亿次高应力接触载荷循环和冲击。基本假设是，MRE 是一种进化优化的折衷方案：1）由于棱柱排列可以局部化损伤并战略性地控制裂纹方向，因此具有令人难以置信的抗断裂性； 2) 通过顺应性蛋白质棱柱鞘，克服羟基磷灰石固有的脆性，从而实现意想不到的强度和韧性； 3) 通过坚硬的、高矿化的、定向的釉质棱柱体表现出耐磨性。该项目将通过两个目标来研究这一假设。 首先，该研究将使用进化生物学方法来识别在马、牛科动物和疣猪中独立进化的 MRE 祖先牙釉质织物特征状态。根据这些信息，将有可能轻松识别釉质织物的特定进化修饰，从而实现研磨并识别可用于进行比较生物力学评估的生物物种。 其次，该项目将通过使用微米和纳米机械工具、光谱学和先进电子显微镜全面表征材料性能，研究牙釉质在多个长度尺度上的结构-性能关系。通过 MRE 磨削的物种的牙齿将与保留祖先牙釉质结构的近亲进行比较，从而揭示显着的解剖学变化，从而实现生物力学特性的优化组合。该奖项反映了 NSF 的法定使命，并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，被认为值得支持。