Probing the Fatigue Mechanisms of Micro-and Nano-Scale Objects

Micro and nano-scale objects are now routinely fabricated with emerging technologies and are employed as structural materials or protective coatings. As such, these objects can be subjected to cyclic loading and can suffer from fatigue degradation. Therefore, there is a need to investigate the fatigue properties of these objects and their governing fatigue mechanisms. This talk discusses the fatigue testing of micro and nano scale materials using microelectromechanical systems (MEMS) for both actuating the fatigue specimens and sensing their responses. Compared to the classical micro-tensile testing techniques, MEMS-based techniques can provide many advantages for measuring the fatigue properties of small-scale materials, including the ability to investigate a large range of fatigue lives (from the low-cycle to the very-high-cycle fatigue regime), the ability to track minute changes in the material’s response throughout the fatigue test, and the ability to perform in situ transmission electron microscopy (TEM) fatigue tests. These techniques are employed to study the fatigue properties of brittle (Si) and ductile (Ni) thin films, ultrathin atomic-layered-deposited (ALD) alumina and titania coatings, and nanocrystalline ultrathin metallic films (Au and Al). In each case, the governing fatigue mechanisms are discussed based on the observed fatigue behavior.