Effect of environment on mechanical properties of micron sized beams of bone fabricated using FIB

Abstract

AbstractBone is a complex material with structural features varying over many different length scales. Lamellae in bone are discrete units of collagen fibril arrays that are the dominant structural feature at length scales of a few microns. The mechanical properties of bone are importantly dependent on the synergy between the lamellae and structural features at other length scales. However, the mechanical properties at this micron level will be indicative of the bone material itself and ignores the structural and geometric organizations prevalent at larger length scales. The isolation of volumes of bone at the lamellar level requires precision cutting methodology and this paper exploits Focused Ion Beam (FIB) methods to mill small cantilever beams from bulk bone material. Importantly, FIB milling can only be performed in a relatively high vacuum environment. Atomic Force Microscopy (AFM) mechanical tests are therefore performed in two environments, high vacuum and air in order to assess the effects of vacuum on bone beam mechanical behaviour. Our results indicate that little difference in the bone beam elastic modulus is found from bending experiments at deflections up to 100nm in different environments.