An Experimental Study of Strength and Fatigue Properties of Materials Used in Micromachines

用于制造集成电路的相同工艺已适用于从陶瓷和金属制造微机电系统（MEMS）。所得到的器件具有几十到几百微米量级的平面尺寸和微米量级的厚度。工程师现在能够设计一个部件，并有信心地预测其整体弹性响应。然而，他们还不能预测允许的静载荷或经受循环载荷的部件的寿命，因为材料的这些特性是不可用的。此外，由于微观结构特征变得越来越重要，因此标准设计实践完全不确定是否可以扩展到如此小的尺寸。本研究项目的第一个目标是测量MEMS中常用的单晶硅、多晶硅和氮化硅等材料的薄试样的强度和疲劳性能。确定这些特性所需的测试将在200微米宽、200微米厚的微样品上进行，样品放在一个带有外部执行器和称重传感器的微小不锈钢负载框架中。该方法的显著特点是在200微米的量规长度上用激光干涉测量直接在试样上测量应变；这避免了试样的整体伸长率用于计算应变时产生的不确定性。该项目的第二个目标是利用强度和疲劳数据来设计一个可以进行评估和测试的原型装置。该装置是一种微型剪刀，能够切割直径为10微米的物体，总长度为150微米。像这样的剪刀有可能用于微创微血管手术。* * *

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. ***