拉格朗日方程在机电系统中的应用

<正> 从物理本质上看,机械系统与电网络中的运动过程完全不同,它们分别用两类物理量描述,服从不同的物理定律.但是,在此基础上所建立的运动微分方程却是相同的.如果把描述这两种系统运动状态的物理量进行类比,我们     

STATIC STUDY OF CANTILEVER BEAM STICTION UNDER ELECTROSTATIC FORCE INFLUENCE

I. INTRODUCTION For capacitor-like microelectromechanical systems (MEMS) structure[1??6], the voltage betweenthe structure and substrate causes attractive force. The sources of the voltage can be an arti?ciallymounted device[2 , 7??9] or the temporar…     

CHARACTERIZATIONS AND RELATIONSHIPS BETWEEN OUTDOOR AND INDOOR BIOAEROSOLS IN AN OFFICE BUILDING

1.IntroductionBioaerosolsaremicroorganismsorparticles,gases,vapors,orfragmentsofbiologicalorigin(i.e.,aliveorreleasedfromalivingorganism)thatexistintheair.Bioaerosolsareeverywhereintheenvironment.Underfavorableconditions,bioaerosolsareabletogrowandpropagateonavarietyofbuildingmaterialsandindoorsurfaces,causingindoorairpollution.Therefore,owingtotheirubiquitouspresenceinnature,bioaerosolsasapollutionsourcearealmostinevitableinarangeofenclosedenvironmentsandincommunityair(Kodama&McGee,1986;Lig…     

静电力作用下的微梁失稳临界电压分析

针对微机械器件中普遍使用的微梁在静电力作用下的变形、吸附、电压与间距等设计问题,以平行板电容器为原型,利用弹性力学中的板梁静力学方程和静电场分布的拉普拉斯方程建立了微悬臂梁的机电耦合模型。将不均匀分布的静电力载荷等效离散为一组集中载荷,对小变形梁应用叠加法求解耦合模型控制方程,得到微梁失去稳定平衡状态的临界电压和梁的挠曲线。结果表明,电压增高,梁的挠度随之增大,达到临界电压时,梁末端的挠度与变形前的间隙之比为 0 42~0 44。     

微光机电(MOEMS)陀螺的技术及发展

提出微光机电(MOEMS)惯性器件技术，对其优势和研究价值进行了理论分析。介绍了国外MOEMS陀螺的工作原理、结构、性能指标及研究状况，初步探讨了微光机电陀螺的应用前景和技术发展途径，以及惯性器件的发展方向。     

藏在手机里的微型陀螺仪

叙述安装在手机内的各种微型振动陀螺仪及其力学原理.     

微电子机械系统中构件的基本力学量检测

本文就近几年在ＭＥＭＳ（ＭｉｃｒｏＥｌｅｃｔｒｏＭｅｃｈａｎｉｃａｌＳｙｓｔｅｍｓ）基本力学量测量技术的最新发展及其特点、意义、进行了较全面的综述。内容包括：ＭＥＭＳ所用材料的基本力学参数测量（如Ｅ、Ｇ、μ），材料的摩擦与摩损的测量，ＭＥＭＳ结构内应力、应变的测量，结构的动态参数和机构运动速度的测量等，为ＭＥＭＳ的研究提供有益的参考。     

用机电耦合模型研究转子系统的非平稳过程

建立恰当的转子系统模型,对非平稳过程进行正确完备的描述是进行转子系统设计、实施状态监测和故障诊断的关键。通过考虑驱动电机的影响,建立了异步电机-受驱转子系统的机电耦合数学模型,并利用该模型对机电转子系统由串联补偿电容和负载波动引起的两种机电耦合非平稳过程进行了数值研究。研究结果表明：建立的机电耦合模型可以多方位地研究转子系统在非平衡过程中的机电耦合动力学规律。     

等离子体沉积碳氟聚合物薄膜的纳米摩擦性能研究

利用原子力显微镜研究了感应等离子体刻蚀加工过程中单晶硅表面形成的不同厚度的碳氟聚合物薄膜的纳米摩擦特性，并针对几种不同的摩擦模式探讨了原子力显微镜探针在不同厚度的碳氟聚合物薄膜表面的摩擦行为．结果表明，同硅基体相比，聚合物薄膜的摩擦力信号明显较弱，薄膜的纳米摩擦特性同其厚度密切相关；碳氟聚合物薄膜在同Si3N4针尖接触过程中可向针尖表面转移，从而对针尖起修饰作用，以减轻微观摩擦磨损．     

SYSTEM OF VECTOR QUASI-EQUILIBRIUM PROBLEMS AND ITS APPLICATIONS

A new system of vector quasi-equilibrium problems is introduced and its existence of solution is proved. As applications, some existence results of weak Pareto equilibrium for both constrained multicriteria games and multicriteria games without constrained correspondences are also shown.     

Dynamics of a Canonical Electrostatic MEMS/NEMS System

The mass-spring model of electrostatically actuated microelectromechanical systems (MEMS) or nanoelectromechanical systems (NEMS) is pervasive in the MEMS and NEMS literature. Nonetheless a rigorous analysis of this model does not exist. Here periodic solutions of the canonical mass-spring model in the viscosity dominated time harmonic regime are studied. Ranges of the dimensionless average applied voltage and dimensionless frequency of voltage variation are delineated such that periodic solutions exist. Parameter ranges where such solutions fail to exist are identified; this provides a dynamic analog to the static “pull-in” instability well known to MEMS/NEMS researchers.      

On the Development of a Mesoscale Friction Tester

MEMS and NEMS devices typically have a large surface area to volume ratio. As a result, a major concern in the development of such devices is friction. Contact radii in MEMS and NEMS devices are expected to range from 10⁻⁸<a<10⁻⁵ m. This regime, which generally lies between the limits of single asperity and macroscopic contact, has yet to be explored because the apparati used to characterize friction at these limits do not operate in the range of forces appropriate to these length scales. A Mesoscale Friction Tester (MFT) with smooth probe tip radii from 50 nm to 50 μm and capable of applying forces ranging from 10 nN to l mN over contact radii from 10 nm to 10 μm has been developed to address this need. With carefully planned experiments, this device has the potential to help answer unresolved questions regarding friction mechanisms in the mesoscale range.     

Ti-6Al-4V钛合金表面疏水性复合膜的制备及其微摩擦磨损性能

通过自组装分子膜（SAMs）方法和有机镀膜技术在Ti-6Al-4V钛合金表面成功制备了三嗪硫醇三乙基硅烷（TES）自组装分子膜（TES-SAMs）和含氟官能团的三嗪硫醇（ATP）复合膜（TES-ATP）.采用X射线光电子能谱仪、接触角测量仪、椭圆偏振光谱仪、原子力显微镜、超景深三维显微镜和UMT-2型摩擦磨损试验机评价薄膜结构及其微摩擦学特性.研究结果表明：TES-SAMs自组装分子膜和TES-ATP复合膜的膜厚分别为3.9和22.2 nm,其对蒸馏水的接触角分别为94.5°和130.5°,呈疏水性.TES-SAMs自组装分子膜和TES-ATP复合膜均能有效降低基体的摩擦系数,TES-SAMs自组装分子膜的摩擦系数稳定在0.23,TES-ATP复合膜的摩擦系数为0.17,而空白基体的摩擦系数为0.50;同时TES-ATP复合膜还表现出良好的抗磨性能.     

THE SURFACE EFFECT ON THE TENSILE STRENGTH OF MICROMACHINED POLYSILICON FILMS FOR MEMS

In order to accomplish reliable mechanical design of MEMS, the influences of surface roughness and octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs) on the mechanical properties of micromachined polysilicon films for MEMS are investigated. Surface effect on the fracture properties of micromachined polysilicon films is evaluated with a new microtensile testing method using a magnet-coil force actuator. Statistical analysis of the surface roughness effects on the tensile strength predicated the surface roughness characterization of polysilicon films being tested and the direct relation of the mechanical properties with the surface roughness features. The fracture strength decreases with the increase of the surface roughness. The octadecyltrichlorosilane self-assembled monolayers coating leads to an increase of the average fracture strength up to 32.46%. Surface roughness and the hydrophobic properties of specimen when coated with OTS films are the two main factors influencing the tensile strength of micromachined polysilicon films for MEMS.     

Multistability of cantilever MEMS/NEMS switches induced by electrostatic and surface forces

MEMS/NEMS switches are used in a variety of portable electronics and RF telecommunications systems. MEMS/NEMS switches are ideally bi-stable, with one ON and one OFF state and a reliable switching between the two induced by electrical actuation. Presented herein is an exploration into non-ideal behavior, i.e. tri-stability, and parametric sensitivity of a generalization of cantilever MEMS/NEMS switches. The representative system model employs multiphysics features based on Euler–Bernoulli beam theory, parallel plate capacitance for electrostatics, and a Lennard-Jones form of surface interaction. The geometry, material properties, and surface features of the device are condensed into just a few dimensionless quantities, creating a parameter space of low enough dimensionality to provide accessible representations of all system equilibria within physically relevant ranges. Analysis of this system model offers insight regarding conditions necessary for bi- and tri-stability in such systems, which are crucial for informing studies on switching dynamics and various device performance metrics.     

Flexural contact in MEMS stiction

Adhesive force between two solid surfaces can lead to stiction failure of the micro-electro-mechanical systems (MEMS) device. The competition between the adhesive force and the beam restoring force determines whether the stiction occurs or not. Previous models assume that the stuck beam deforms either as the arc-shape or the S-shape, which causes significant differences in the measurements of adhesion and disputations among researchers. The contact mechanics model presented in this paper shows that the assumptions of the arc-shape and S-shape on the beam deformation over-simplify the problem; both the arc-shaped deformation and S-shaped deformation significantly deviate from the real ones. The previous theories are shown to be incompatible with the recent experimental results. The model presented in this paper attempts to explain those new experimental results and resolve some disputations on the previous models. The instabilities of jump-in during loading process and jump-off during unloading process are also incorporated in this model.     

紫外照射对FOTS自组装分子膜表面特性和摩擦特性的影响

利用自组装技术在硅基底制备FOTS自组装分子膜,对FOTS自组装分子膜进行紫外照射.采用接触角测量仪、原子力显微镜(AFM)、傅里叶红外变换光谱仪(FTIR)、X光电子能谱(XPS)和多功能摩擦磨损试验机(UMT)评价薄膜的表面特性和摩擦学特性.结果表明:FOTS自组装分子膜的蒸馏水接触角为109°.紫外照射导致C元素被O₃氧化,形成亲水的-COOH末端基团,使其接触角变小,表面粗糙度增大.在微载荷下,FOTS自组装分子膜和经不同时间紫外照射的FOTS自组装分子膜均可降低硅基底的摩擦和磨损.紫外照射后使FOTS自组装分子膜的摩擦系数增大,磨损加剧,这与其表面结构和润湿性变化相关.     

CONCAVE BIOLOGICAL SURFACES FOR STRONG WET ADHESION

Plant leaves, insects and geckos are masters of adhesion or anti-adhesion by smartly designed refined surface structures with micro- and nano- ＇technologies＇. Understanding the basic principles in the design of the unique surface structures is of great importance in the manufacture or synthesis of micro- and nano- devices in MEMS or NEMS. This study is right inspired by this effort, focusing on the mechanics of wet adhesion between fibers having concave tips and a flat substrate via capillary forces. We show that the concave surface can effectively enhance the wet adhesion by reducing the effective contact angle of the fiber, firmly pinning the liquid bridge at its circumferential edge. A critical contact angle is identified below which the adhesion strength can achieve its maximum, being insensitive to the contact angle between the fiber and liquid. The analytical expression for the critical angle is derived. Then a tentative design for the profile of concave surfaces is proposed, considering the effects of chamfering size, deformation and buckling, etc. The effect of liquid volume on the wet adhesion of multiple-fiber system is also discussed.     

微重力环境下硅基纳米器件碰撞滑动接触问题研究

随着纳米技术的发展,微机电系统被广泛应用于微纳卫星、皮卫星以及各种高精密仪器. 单晶硅广泛应用于微机电系统,考虑微重力环境空间机构无规则碰撞的运动特性,建立刚性金刚石压头与弹性硅基体之间碰撞滑动接触的分子动力学模型,对比研究压头不同振动频率和振幅对平均摩擦力的影响. 结果表明:压头振动频率低于基体固有频率时,平均摩擦力无明显变化,而高于固有频率时,平均摩擦力随振动频率增大呈现先减小后不变的趋势;振幅的增大导致压头和基体的碰撞更加剧烈,剧烈的碰撞导致基体表面更多原子晶格结构破坏,失效原子数增多,降低了平均摩擦力;在基体表面引入纹理,发现纹理表面能够有效降低平均摩擦力.      

多烷基环戊烷/有机硅烷双层膜的制备及摩擦学性能研究

分别在羟基化硅片表面制备了多烷基环戊烷单组分润滑膜(MACs)、(3-胺丙基)三乙氧基硅烷自组装膜(APS-SAMs)和多烷基环戊烷/(3-胺丙基)三乙氧基硅烷双层润滑膜(MACs-APS),对比研究了不同润滑防护涂层的摩擦磨损性能.结果表明:在载荷0.1N、频率1Hz下,与APS-SAMs和MACs单组分膜相比,MACs-APS双层膜在保持较低摩擦系数的基础上,其耐磨性能显著提高,在失效前未发生明显磨损.在所制备的这种双层润滑薄膜体系中,流动性较好的MACs分子镶嵌在固定相APS-SAMs的网络中,因而产生较好的复合摩擦学性能.