9313302 Sharpe The same processes used to make integrated circuits have been adapted to fabricate microelectromechanical systems (MEMS) from ceramics and metals. The resulting device has planar dimensions on the order of tens to hundreds of micrometers and thicknesses on the order of micrometers. Engineers are now able to design a component and predict its overall elastic response with confidence. However, they cannot yet predict the allowable static load or the life of a component subjected to cyclic loading because those properties of the materials are not available. Furthermore, it is not at all certain that standard design practices will scale to such a small size because the microstructural features become increasingly important. The first objective of this research project is to measure the strength and fatigue properties of thin specimens of materials such as single- and poly- crystalline silicon and silicon nitride that are commonly used in MEMS. The testing required to ascertain these properties will be performed on microsamples 200 micrometers wide by 200 micrometers thick in a tiny stainless steel load frame with an external actuator and load cell. The significant feature of this method is that strain is measured directly on the specimen over a gage length of 200 micrometers with laser interferometry; this avoids the uncertainties that arise when the overall elongation of the specimen is used to compute strain. The second objective of the project is to use the strength and fatigue data to design a prototype device that can be evaluated and tested. The device is a micro-scissors capable of cutting 10 micrometers diameter objects and having an overall length of 150 micrometers. Scissors like these have potential for use in minimally invasive microvascular surgery. ***
