Regensburg 2004 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 13: SYMPOSIUM: Understanding and Controlling Complex Structures: From Synthetic Polymers to Biomaterials I

CPP 13.1: Invited Talk

Tuesday, March 9, 2004, 09:30–10:00, H 37

Hierarchical Structures in Biological Materials — •Peter Fratzl — Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, D-14424 Potsdam

Natural mineralized tissues such as wood, collagen or bone are hierarchically structured and optimized for mechanical performance at all levels of hierarchy. The basic unit of bone is a collagen fibril reinforced with calcium phosphate nanoparticles. Such fibrils are assembled into a complex composite structure which is far from being completely understood. The hierarchical structure in wood consists of parallel tubes (the wood cells) with polymeric walls reinforced by thin cellulose fibrils. Adaptive growth and remodelling are common denominators in biological materials and responsible for functional adaptation all hierarchical levels. A successful approach to study hierarchical structures and their mechanisms of deformation is scanning microfocus x-ray scattering complemented with scanning electron microscopy and nanoindentation. Size, shape and arrangement of mineral nanoparticles in bone are found by such methods to vary systematically with age or at interfaces. Their detailed arrangement turns out to be essential for the mechanical performance of the composite, since they seem to control both the rigidity and the toughness of the tissue. Quite similarly, recent results show that the exact geometrical arrangement of the cellulose fibrils in the plant cell wall controls to a large extent its mechanical bahaviour. In conclusion, mechanical behaviour seems to depend essentially on the complexity of the structure which is controlled by functional adaptation.