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 troublesome problems in microfabrication and operation processes when the separations of components in microelectromechanical systems are in the sub-micrometre regime. Some hitherto neglected mechanical effects, including the quantum mechanical effect, should be taken into account for solving the problems. The magnitude of the Casimir force is significant when the membranes work in vacuum without the effect of capillary forces. In this paper, an analysis is presented of the influence of the Casimir effect with surface roughness, conductivity and temperature corrected on the deformation of a membrane strip structure. With nothing other than the Casimir force loading the strip, a stable static equilibrium state and an unstable static equilibrium state exist, depending on the value of a dimensionless constant K. The membrane strip will collapse if the value of K is larger than the critical value of KC. The critical value of KC varies with the value of wo. This provides a way to check if a system with given dimensions and material properties will be in a stable equilibrium. This also provides a way of designing a membrane strip with high resistance to collapse.

In the present study, high-Tc superconducting thin YBa2Cu3O7 films and polysilicon films were prepared to investigate the initial sliding friction properties using a ball-on-flat tribometer when samples were moved against a sapphire ball or a steel ball in ambient environment. The surface topography was measured with atomic force microscope (AFM). After five times testing, the experimental results indicate that the friction coefficient of YBa2Cu3O7 films is lower than that of polysilicon films when sliding against a sapphire ball and almost the same when sliding against a steel ball. In particular, the initial friction of YBa2Cu3O7 films is more stable when sliding against a sapphire ball. However, the initial friction of polysilicon films fluctuates during a cycle period when sliding against a sapphire ball. They are both stable when sliding against a steel ball. Although, the surface profile of the YBa2Cu3O7 film is rough and can be seen to be rougher than the polysilicon film, but the friction coefficient of the YBa2Cu3O7 film is lower than that of polysilicon film. Also, although the topography of YBa2Cu3O7 films changes during friction, the friction coefficients are stable. This clearly shows that the initial sliding friction of YBa2Cu3O7 films under microfriction is stable. The observation signifies YBCO film is a good film to prevent stick-slip motion in ambient environment. The wear properties of YBa2Cu3O7 films suggest that the superconducting outgrowths (CuO) are loose and they can be easily removed.

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.

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.