Microscale Characterization of Mechanical Properties

Lilliputian techniques for measuring the mechanical response of microscale specimens are being developed to characterize the performance and reliability of microelectromechanical systems (MEMS) and other small-scale entities. The challenges associated with the preparation, handling, and testing of small volumes of material have spawned a variety of techniques; this review focuses on uniaxial testing. Results from these experiments provide valuable insight into size-scale effects on the elastic, brittle, and ductile behavior of micron-sized structures. Fundamental elastic interactions show no size effect; in-plane moduli can be predicted from anisotropic elastic constants if crystallographic texture is properly considered. Intrinsic fracture toughness is also size independent, although the fracture strength of brittle MEMS materials is extremely dependent on flaw size and distribution. By contrast, size effects on the strength of ductile materials suggest that the operation of intrinsic dislocation processes in greatly reduced or confined volumes alters their generation, multiplication, interaction, and motion.