微型机电系统（MEMS）是面向21世纪的关键技术，微型机械的设计与制造在很大程度上取决于材料问题的解决。影响微型机械装置功能和可靠性的薄膜材料力学性能需要精确的评价。利用电磁力驱动，设计了一种微拉伸装置，从而精确地测定了长度为100-660μm，宽度为20-200μm，厚度为2.4μm的多晶硅薄膜的力学性能。结果表明，测得的平均弹性模量为164 GPa±1.2 GPa，与理论计算值相当。平均拉伸强度为1.36 GPa±0.14 GPa，其威布尔分布参量为10.4-11.7。统计分析表明，由于微结构和尺寸的约束使得多晶硅薄膜的拉伸强度表现出对微构件长度、表面积和体积的尺寸效应。拉伸强度随表面积与体积之比值增加而增加，这一比值可作为尺寸效应的控制参量。测试数据解释了微构件力学性能参量的离散性，并可用于多晶硅微机械的可靠性设计。最后，提出了应变设计准则，允许应变为0.0057。

Mechanical stability and sticking are the troublesome problems in microfabrication and operation processes when separations of components in MEMS are in the sub-micrometer regime. Some mechanical effect, including quantum mechanical effect should be taken into account for solving the problems. The influence of capillary forces on sticking of a surface micromachined microcantilever in ambient environment or the rinse liquid and the influence of quantum mechanical effect such as the Casimir effect on sticking and stability of a micro membrane strip cavity structure in vacuum were investigated. A factual rough model theory about sticking problem under the Casimir effect was suggested for the first time. The study on the design of anti-sticking structures under different forces shows that sticking and stability of microcantilevers and micro membrane strip cavities has something to do with Young's modulus of materials, surface properties, length of structures, thickness of structures and separation between the fixed surface and the deflecting component. But, it is independent of width of structures. The map of the size design of anti-sticking structures was put forward for the first time. This also provides a way to design a MEMS structure with high resistance to collapse.

The increasing use of small micromechanical devices and advanced sensors has led to concern about the failure modes and reliability of these structures. The enormous promise will not materialize without substantial progress in overcoming the stiction, friction and wear associated with such devices and understanding the mechanical behavior of MEMS materials and structures. Self-assembled monolayers (SAMs) are release and anti-stiction coatings for MEMS. In this paper, the anti-stiction properties of octadecyltrichlorosilane (OTS) SAM were calculated. The microtribological properties of OTS SAM were investigated with a ball-on-flat microtribometer. The influence of OTS SAM on the mechanical properties of micromachined polysilicon films for MEMS was investigated with an accurate evaluation using the microtensile test device. It was concluded that the OTS SAM has good anti-stiction properties and low friction coefficients. The hydrophobic property of OTS is the main factor leading to an increase in the average fracture strength of micromachined polysilicon up to 32.46%. Thus, the operational stability and lifetime of MEMS can be raised when coated with self-assembled monolayers.

A molecular dynamics simulation is used to investigate the effect of surface roughness on the nano-rheology of ultra-thin films confined between two solid walls. The results show that friction is sensitive to the confining surface morphology and the fluid molecules near the two confining surfaces are in a layering solid-like structure. At a high shear rate, the interfacial layers of the film stick to the walls, resulting in partial slip inside the film and the development of shear stress in the viscous molecular fluid. The frictional resisting force is due to the shear in the viscous molecular fluid but not dependent on the critical yield stress of the solid-like structure as in the case of smooth boundaries.

The nanoindentation fracture of multilayer hard coatings of TiNrTi C,N.rTiC, Al2O3rTiCrTi C,N.rTiC, TiNrTi C,N.rTiCrTi C,N.rTiC and TiNrTi C,N.rTiCrTi C,N.rTiCrTi C,N.rTiC, deposited on cemented carbide using a CVD technique was studied. Based on an analysis of the energy released in cracking, the calculated fracture toughness values of these coatings were 2.18, 1.74, 3.40 and 3.90 MPa m1r2, respectively. Both load-penetration depth and loadl penetration depth squared plots have been demonstrated to be necessary if a more complete understanding of the coating system behaviour is to be gained. The interfacial failure and the critical load of interfacial failure of these coatings were also discussed. A step was found in the forcel displacement curves at the onset of coating fracture. A straight line segment in the oad-penetration depth squared curves was discussed. The hardness, fracture toughness and anti-wearability of these coatings were compared. The results show that the fracture toughness and anti-wearability are getting higher with the layers increasing.