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Antlers are tough due to their organization at nano level


Antler bone derives its extraordinary biomechanical qualities from nanofibres of mineralized collagen fibrils (MCFs) that are held together in small bundles by non-collagenous proteins (NCPs). In this study, Hang et al. investigated the interface between the two entities and how this contributes to the overall strength of the material.

The authors used an atomic force microscopy tip to pull out individual mineralized collagen fibrils from the fracture surface of antler bone, measuring how much force was required to pull out a fibre. They showed that the force needed increased to the point where the MCF-NCP interface failed. The strength of the interface between the fibrils and the surrounding non-collagenous proteins could be estimated from the force-deflection curves and the dimensions of the fibrils.

For individual fibrils, the adhesion forces were relatively weak but the sheer number of fibrils and the small diameter of each one means that the entire interfacial surface area is large and provides a huge number of potential nanoscale cracking pathways. The extent of the area available at the nanoscale interfaces between MCFs and NCPs in antler bone confers substantial energy absorbing properties.

Editor’s comment: The low values observed for individual MCFs suggest that the interaction with NCPs is rate-dependent with a potential role for the sacrificial ionic bonds.

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