Progress Report Size Matters Mechanical Properties of Materials at the Nano-scale

At the nano-scale, yield and fracture strengths, for example, have been found to deviate from classical mechanics laws and, therefore, can no longer be inferred from the bulk (large-scale) response or from the literature. Unfortunately, the few existing conventional experimental techniques for assessing mechanical properties at this scale are insufficient, not easily accessible, and generally limited to thin films. In order to design reliable devices, a fundamental understanding of mechanical properties as a function of feature size is desperately needed. The key remaining question is whether materials really are stronger at the sub-micron scale, and, if so, then why and how. A major component of my research is the development of innovative experimental approaches to assess the mechanical properties of materials whose dimensions have been reduced to the nano-scale not only vertically, as is the case for thin films, but also laterally. To enable the development of innovative experimental approaches, when I first arrived at Caltech in 2007, my colleague Dr. Warren Oliver built a unique in-situ mechanical deformation instrument called SEMentor (Figure 1) based on concepts that I had develSize Matters Mechanical Properties of Materials at the Nano-scale