Structural Biological Materials

Dr. Joanna McKittrick
Dept. of Mechanical and Aerospace Engineering and
Materials Science and Engineering Program
University of California, San Diego

The study of materials that have evolved through millions of years of evolution and natural selection can provide insights into heretofore-unexploited mechanisms of toughening. Structural biological materials such as mollusk shells, bones and teeth have hierarchical assembly from the nanoscale to the macroscale. Other defining features are multifunctionality, self-assembly under ambient conditions and adaptability. Most biological systems are grown through a bottom-up strategy, in contrast with conventional synthesis methods, which have been mainly top-down manufacturing methods. These materials are lightweight with densities < 3 gm/cm3 and are composed of a limited number of elements, yielding specific strengths, elastic modulus and toughness values that are extraordinarily high. These provide a new paradigm as the basis for bioinspired materials design.

This talk will broadly cover some of the research at UCSD on structural biological materials. Mollusk shells, bones and antlers, teeth and tusks, horns, arthropod exoskeletons and avian feathers and beaks will be discussed and parallels will be drawn. The emphasis will be on the quasi-static and dynamic mechanical properties (tension, compression, shear and bending testing) and microstructural features that act to enhance the properties. Microstructural features such as selective porosity, porosity gradients, biopolymer/mineral interaction and the presence of fibrous proteins or polysaccharides all act to toughen the materials.

The processes of biomineralization involve the secretion of proteins, and complex supramolecular protein structures, along with other biopolymers such as polysaccharides and genetic messages. Biomineralization of mollusk shells and demineralization/deproteinization of bone will be discussed.

Joanna McKittrick is a Professor of Materials Science and Engineering in the Department of Mechanical and Aerospace Engineering at UC San Diego. She holds a B.S. in Mechanical Engineering from the University of Colorado, a M.S. in Materials Science and Engineering from Northwestern University and a Ph.D. from MIT. Her research interests include structural biological materials, biomineralization, biomimetic processing, powder synthesis and luminescence properties of oxides and nitrides.