Title: Protein materials balance strength, energy dissipation and robustness by selecting nanopatterned, hierarchical feature

Speaker: Markus J. Buehler, MIT
Laboratory for Atomistic and Molecular Mechanics,
Department of Civil and Environmental Engineering,
Massachusetts Institute of Technology,
77 Massachusetts Avenue, Room 1-272,
Cambridge, Massachusetts 02139, USA

Date/Time: March 29th, 2007 2pm - 3pm, San Diego Supercomputer Center Rm 462

Abstract: Deformation and fracture are fundamental phenomena with major implications on the stability and reliability of machines, buildings and biological systems. All deformation processes begin with erratic motion of individual atoms around flaws or defects that quickly evolve into formation of macroscopic fractures as chemical bonds rupture rapidly, eventually compromising the integrity of the entire structure. However, most existing theories of fracture treat matter as a continuum, neglecting the existence of atoms or nanoscopic features. Clearly, such a description is questionable. Here we discuss an atomistic approach to describe such processes using ultra large-scale molecular dynamics (MD) simulation implemented supercomputers. MD provides unparalleled insight into the complex atomic-scale deformation processes, linking nano to macro, without relying on empirical input, since all atomic interaction parameters can be derived from fundamental quantum chemical theories. We demonstrate how MD can be used within a multi-scale simulation framework to predict the elastic and fracture properties of hierarchical protein materials, marvelous examples of structural designs that balance a multitude of tasks, representing some of the most sustainable material solutions that integrate structure and function across the scales. Breaking the material into its building blocks enables us to perform systematic studies of how microscopic design features influence the mechanical behavior at larger scales. We review studies of collagen Natures super-glue, spider silk a natural fiber that can reach the strength of a steel cable, as well as intermediate filaments an important class of structural proteins responsible for the mechanical integrity of cells, which, if flawed, can cause serious diseases such as the rapid aging disease progeria. The common ground of these examples is the significance of the material properties at large deformation, its alteration under stress, presence of defects or the effect of variation of environmental conditions. Our studies elucidate intriguing material concepts that enable to balance strength, energy dissipation and robustness by selecting nanopatterned, hierarchical features.

Brief biography: After education at the University of Stuttgart, Germany in Chemical and Process Engineering, Prof. Markus Buehler received his M.S. degree in Engineering Mechanics from Michigan Technological University, USA, in 2001. From 2001 to 2004 he worked at the Max Planck Institute for Metals Research in Stuttgart, Germany as a research assistant from where he also received his Ph.D. in Chemistry. From 2004 to 2005, Prof. Buehler hold an appointment as the Director of Multiscale Modeling and Software Integration at the Materials and Process Simulation Center at the California Institute of Technology, overseeing multiscale method development and applications in modeling of small-scale materials phenomena, with a particular focus on coupling of chemical processes and mechanical properties. In 2005, he joined the Massachusetts Institute of Technology (MIT) to assume a faculty appointment in the Department of Civil and Environmental Engineering (CEE). Prof. Buehler founded MITs Laboratory for Atomistic and Molecular Mechanics, where his research is focused on multi-scale modeling of complex hierarchical protein materials. He is currently the associate editor of the Journal of Computational and Theoretical Nanoscience and guest editor of the Journal of Materials Science. He has made significant contributions in the field of atomistic and molecular modeling of deformation and fracture of brittle, ductile and biological materials. Prof. Buehler has received several awards, including the Materials Research Society Gold Graduate Student award and the National Science Foundation CAREER award.