Plenary Lecture

Professor Peter Fratzl
Director of the Max Planck Institute of Colloids and Interfaces,
 Potsdam, Germany

"How Interfaces Control the Mechanical Behavior of Biological Materials"

Biological materials, such as wood, grasses, protein fibres, bone, sea shells or glass sponges are generally composites of different types of polymers as well as mineral. These materials are able to adapt to the mechanical requirements of the environment by growing and assembling structural components in a hierarchical fashion. This implies the existence of various types of interfaces at all levels of hierarchy. From a mechanical viewpoint, interfaces may be considered as defects but, in many natural materials, interface structures emerged which improve rather than deteriorate the overall mechanical properties of the composite. Bone, for example, consists in about equal amounts of a collagen-rich matrix and calcium-phosphate nano-particles. These components are joined in a complex hierarchy of fibres and lamellar structures to a material with exceptional fracture resistance. Similarly, tendon collagen consists of an assembly of fibrils which partly deform by shearing the interface between them. An example for self-healing properties due to molecular-scale interfaces is the byssus fibre used by mussels to attach to rocks. These fibres combine large deformation with stiffness and abrasion resistance. Finally, plant cell walls generate internal stresses and even complex movements upon changes of environmental humidity. This force generation and actuation capabilities are based on water swelling of hemicellulose-rich interfaces between cellulose microfibrils arranged in complex architectures. Unravelling the structural principles of these unexpected material properties may indicate ways towards new types of composite materials with adaptive capabilities.

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Biographical sketch

Peter Fratzl is director at the Max Planck Institute of Colloids and Interfaces in Potsdam, Germany, and honorary professor of physics at Humboldt University, Berlin, and at Potsdam University. He received an engineering degree from the Ecole Polytechnique in Paris, France (1980), and a doctorate in Physics from the University of Vienna, Austria (1983). Before moving to Potsdam in 2003, he has been holding professor positions in materials physics at the Universities of Vienna and Leoben in Austria and been director of the Erich Schmid Institute of materials science of the Austrian Academy of Sciences.

Peter Fratzl’s lab studies the relation between (hierarchical) structure and mechanical behaviour of biological materials, such as mineralized tissues, extracellular matrix, or plant cell walls, as well as bio-inspired composite materials. This is complemented by medically oriented research on osteoporosis and bone regeneration. Peter Fratzl has published more than 350 papers in journals and books, mostly on interdisciplinary materials science topics. He received several international awards for his work including the Max Planck Research Award 2008 from the Humboldt Foundation (together with Robert Langer, MIT) and the Leibniz Award 2010 of the German Science Foundation. In 2010, he was awarded an honorary doctorate from the University of Montpellier, France, and since 2007 he is foreign member of the Austrian Academy of Sciences.

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