The unusually high strength exhibited by many nanoscale materials has been a topic of discussion since the phenomenon was observed in metal whiskers in the 1950s. While the role of defects and dislocations in the mechanical properties of bulk materials is fairly well known, the theories developed to predict and explain the properties of bulk materials cannot always be extended to nanoscale volumes. Novel methods of testing nanoscale structures have been developed to measure the size-dependent strength of materials.
Nanoscale structures such as pillars and beams are particularly well suited for in-situ mechanical testing. Prior to testing, electron microscope imaging gives the user a direct view of tip placement and confirmation of proper alignment. This alignment can be performed without ever contacting the sample, leaving the specimen in pristine condition for testing. Both the indenter probe and sample can be verified to be free of contamination and preexisting defects, if present, can be identified. During the mechanical test, the real-time video gives insight into deformation and failure modes. Pillar or beam dimensions can also be easily measured, facilitating the straightforward calculation of values such as stress/strain and fracture toughness.