Collaborative Research: Bone as an interpenetrating composite material

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Non-Technical Abstract: This collaborative project award by the Biomaterials program in the Division of Materials Research to University of Illinois Urbana-Champion and University of California San Diego is to investigate a new model of bone as a material that the two phases in bone, proteins and minerals, are interpenetrating (continuous), and to explore what implications this hypothesis has on bone's mechanical properties, including strength and resistance to fracture. Bone is made of collagen and other proteins, nano-sized minerals and water, all hierarchically self-assembled. Bone has excellent properties due to its complex hierarchical structure; it is strong, stiff, tough and light weight. However, factors contributing to these superior properties are still not well understood. This fundamental and interdisciplinary study will include state-of-the art experiments and multiscale modeling, and will focus on porcine developing bone (0-48 months) which exhibits significant changes in its structure and composition with age. Results from this research will lead to better predictions of bone quality in humans, which is still an outstanding clinical issue, and will guide in the design of novel synthetic composite materials with superior mechanical properties for applications in biomedical, transportation and energy fields. Students from diverse backgrounds will participate in this cutting-edge research. New courses will be developed and short courses and other presentations will be given to technical and lay audiences. Technical Abstract: Bone is a biological nanocomposite material made of collagen and other proteins, hydroxyapatite minerals and water, all hierarchically assembled. This complex structure gives bone its superior properties (strong, stiff, tough and light weight). However, the contributing factors are still not well understood. In this collaborative project, researchers will test two hypotheses: 1) bone is a composite material made of interpenetrating organic and mineral phases; and 2) synthetic bioinspired composites with interpenetrating phases will have superior mechanical properties, compared to composites with a dispersed reinforcing phase. More specifically, these investigators will determine if the interpenetrating model is valid for bone with varying degrees of mineralization and different microstructures via multiscale experiments and modeling. Developing porcine bone (0-48 months old), which exhibits a range of microstructures and mineral contents will be studied as part of this project. Strains at the collagen/mineral level as a function of applied stress, using high energy x-rays diffracting at small- and wide-angles, will be compared with those obtained theoretically. In addition, synthetic bioinspired materials with interpenetrating phases will be designed and tested, and their properties compared to those of composites with a dispersed reinforcement. This project is expected to provide fundamental understanding of bone's hierarchical structure, which will lead to better predictions of bone quality and will guide the design of new bioinspired synthetic composites for different applications. Students from diverse backgrounds are expected to participate in this cutting-edge research, including the students from Title V Hispanic-serving high schools. New courses will be developed, and presentations will be given to technical and lay audiences.