Characteristic dimensions and the micro-mechanisms of fracture and fatigue in 'nano' and 'bio' materials

The behavior of small-volume (so-called 'nano') structures, where size-scales are comparable with microstructural dimensions, and biological/bio-implantable materials, which invariably display a hierarchy of structural dimensions, is currently much in vogue in materials science. One aspect of this field, which to date has received only limited attention, is the fracture and fatigue properties of these materials. In this paper, we examine two topics in this area, namely the premature fatigue failure of silicon-based micron-scale structures for microelectromechanical systems (MEMS), and the fracture properties of mineralized tissue, specifically human bone.