Multiscale mechanics of bone
Multiscale characteristics of bone toughness
Toughness in bone arises from several mechanisms which act at multiple length scales in the bone hierarchical structure. In order to comprehensively investigate the toughening in bone, various parameters are measured in pathalogic mouse models of bone and related across the length-scales. At nano-scale, mineral crystal size and fibular strain are measured by wide and small angle x-ray scattering analysis. Other compositional properties of the bone matrix such as the mineral to collagen ratio and properties of the bone mineral are measured using Fourier transform infrared spectroscopy and thermogravimetric analysis. At micro-scale, material and the elastic modulus heterogeneity are characterized using quantitative scanning electron microscopy and nanoindentation techniques, respectively.
In the next level of bone hierarchy, fracture toughness of the whole bone is measured by loading the mouse femur and monitoring the length of the crack as it propagates. This multiscale analysis gives insight into various ways that bone gets tough through material and structural alternations at its hierarchy.
Bone scaling across species
Across animal species bone must support varied mass and locomotor activities. In this project we looked at bone scaling in the appendicular skeleton in felids (cats), artiodactyls (hoofed animals), macropods (kangaroos), and bipedal birds to understand how bone structure changes in response to increases in body size and locomotor habits.
Collaborators: Dr. John Hutchinson (Royal Veterinary College)
Characterizing fracture toughness in murine bones
Assessing bone quality is critical in understanding pathology and determining efficacy of therapy. Fracture toughness is a measure of how easy it is to break a bone. In this project we developed methods for creating resistance curves and calculating fracture toughness in mouse bones.
Collaborators: Professor Rob Ritchie (U.C. Berkeley)
Examining the collagen/apatite interface
Collagen is the protein template on which mineral hydroxyapatite forms in bone. Together they account for the tensile and compressive properties of bone. In this project we use analytical transmission electron microscopy to examine the biochemical composition of the interface.
Collaborators: Dr. Alex Porter (Imperial College London), Professor David McComb (Ohio State Univ)