The Study On Micro-nano Mechanical Behaviors Of Bone Via Novel In-situ Mechanical Testing

As human important supporting organ,bone can protect human organs and support hu-man stable movement.Bone has typical hierarchical structure,the composite of bony units of structure at different scales and the interaction or cooperation of bony units determine bone me-chanical property.The research on mechanical property of bony basic structure units has always been research hot spots in the field of study of bone mechanics,especially,doing research on bone structural units at micro and nano scale can help reveal nature of bony good mechanical property such as bony high fracture toughness,understand disease's effects on bone mechanical property,develop bionic bone repair materials a lot.With development of micro mechanical testing method,the research on bone mechanical property at micro and nano scale has been developed a lot.The use of test method such as X-ray synchrotron radiation,in-situ micro-CT,molecular dynamics simulation and simulation calculation make us understand bone mechanical property and toughing mechanism deeper,but the direct research on bone mechanical property is still hard to see.In order to understand bone mechanical property at micro and nano scale deep,this research successfully develop a novel in-situ mechanical testing device by combining AFM and MEMS,meanwhile do research on bone mechanical property at micro and nano scale,evaluate the effects of free water and bonding water on bone toughness and qualify the contribu-tion of different cracks to bone toughness.The developed in-situ mechanical testing device can characterize the structure and force situation stably and instantly;in-situ testing prove the ef-fectiveness of developed in-situ testing device;the research on bone mechanical property prove that the exist of free water and bonding water can make bone more tough;and the research on the surface energy consumed by cracks's expansion shows that the surface energy of cracks going through osteons contributes more to bone toughness.By using in-situ mechanical testing,we successfully record the basic units of bone at nano scale when crack expands,record the sliding and the broken behavior of MCFs and in-situ observing micro-bridging for the first time.The research on bone mechanical property shows that the remove of free water and bonding water can decrease bone toughness and increase isotropic of bone mechanical property;by doing re-search on mechanical behavior of dehydrated bone samples in vacuum environment,we think that the numeric decreased hydrogen bonds resulted from the remove of free water and bonding water of MCFs system make the surface energy of osteons close to the surface energy of cement lines and lead to the straighter cracks' expansion path and decreased bone toughness.The re-search on the surface energy consumed by cracks's expansion further clarified that comparing to the crack expanding along cement lines cracks going through osteons consume more interface energy,therefore it contributes more to bone macro fracture toughness.