Micro/nano mechanical characterization of one-dimensional nanomaterials and biomaterials

This dissertation focuses on the experimental micro/nano mechanics of two material systems: one-dimensional (1-D) nanomaterials and biomaterials. The objectives have been achieved by implementing micro/nano mechanical characterization on representative materials and investigating their deformation behaviors and underlying physical mechanisms. The findings are significant for providing the guidelines of rational design of micro/nano devices and biomaterials.;Size effects for low dimensional nanomaterials are far from comprehension. In the first part of the dissertation, the mechanical properties of representative 1-D nanomaterials were measured by nanoindentation, atomic force microscope (AFM) bending, and nanobuckling. Compared with bulk entities, the nanomaterials studied show a decrease in elastic modulus. It is proposed that high surface-to-volume ratio of the nanomaterials, crack propagation, as well as surface stresses, all come together to play key roles in governing the size dependent mechanical properties. Nanomachining has been difficult to interact directly with nanostructures. A nanoindenter integrated with an AFM is demonstrated to be a powerful tool for cutting 1-D nanomaterials to precise lengths, and it permits direct mechanical machining of nanodevices.;The second part is centered on the micro/nano studies of deformation behaviors and fracture failure of biomaterials. Based on micro tensile testing of type-I collagens, the elastic modulus and tensile strength are found to be improved through UV irradiation, and collagen fibril reinforcement. Cross-links and interlocking of the microstructures are believed to be the main reasons for the mechanical property enhancement. Efforts in the second section are directed to virus-templated biocomposites. The polyaniline coated tobacco mosaic virus nanotube is an ideal model to study the elastic modulus and deformation behavior of core-shell nanotubes. In this contribution, the biocomposite were characterized with reference to their mechanical response, coating characteristics and interface interaction. The elastic modulus was measured to be within that of the constituent materials. Delamination in nonlinear deformation is attributed to the weak bonding, the residual stress of the coating, and different rigidities of the constituent materials.