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1.
利用电磁力驱动微拉伸装置,考察多晶硅微构件表面粗糙度和施加表面分子自组装膜(octadecyltrichlorosilane,简称OTS)对抗拉强度及断裂损伤的影响。结果表明,微构件的抗拉强度表现出依赖表面性质的表面效应。抗拉强度随表面粗糙度的增加而降低,并受环境气氛的影响。当构件表面施加表面分子自组装膜后,在以上两因素的作用下.多晶硅微构件的抗拉强度提高了32.46%。研究结果可用于微机械构件的材料表面改性设计。 相似文献
2.
Despite much progress in surface micromachining technology, adhesion, friction and wear remain key issues, severely limiting the realization and reliability of many microelectromechanical systems (MEMS) devices. In this article, we focus on the use of molecularly thin organic films as release and anti-stiction coatings for MEMS. The various classes of organic films explored for MEMS are reviewed here, followed by a discussion of the current limitations and areas for improvements for this coating technology. 相似文献
3.
The equilibrium adsorption of gas phase alcohol molecules has been proposed as a new means of in-use anti-stiction and lubrication for MEMS devices. Adhesion and friction of silicon oxide surfaces as a function of n-propanol vapor pressure in the ambient gas were invesitigated using atomic force microscopy. As the vapor pressure increases, the adsorbed n-propanol layer thickness increases. The adhesion and friction significantly decrease with very little addition of n-propanol vapor. 相似文献
4.
《Tribology - Materials, Surfaces & Interfaces》2013,7(2):75-83
AbstractSilicon nitride as an energy efficient material is replacing conventional steels for new generation engineering components such as bearings, cutting tools, electronics and engine parts in automotive, aerospace and wind industries. Compared with steel bearings, silicon nitride bearings can be operated at much higher temperatures and speeds with >60% weight reduction and up to 80% friction reduction. These are all due to its unique material properties, including high wear and corrosion resistance, low density and heat generation. Current lubrication solutions for hybrid contacts, where silicon nitride balls and steel races are used, are mostly relying on the protection film formed on the metal surfaces. Self-assembled monolayers (SAMs) have been found very useful in modifying surfaces, especially for microelectromechanical system and nanoscale applications, e.g. atomic force microscopy tips, etc. This study aims to investigate the feasibility of forming a SAM protection film on industrial grade bearing material silicon nitride to reduce the friction for the oil lubricated hybrid contacts. Four silanes with different functional head groups, including octadecyltrichlorosilane (OTS), octyltrichlorosilane, chlorodimethyloctadecylsilane and octadecyltrimethoxysilane, were initially investigated to form SAMs on industrial grade silicon nitride surfaces. The effects of concentration and immersion time of the silanes on the formation of SAMs on the silicon nitride surface were evaluated using contact angle measurements. The preliminary results show that the wetting properties of the silicon nitride surface can be effectively modified by the formation of SAMs from the silane solutions. OTS can form an order and compact SAM on the silicon nitride surfaces within 2 min at the concentration of 2··5 mM in decane solution, while the other three alkylsilanes can also effectively modify silicon nitride surfaces given sufficient immersion time, e.g. over 1 h. Tribological tests were subsequently carried out on a ball on disc rig where a steel ball and a silicon nitride disc were used. The effect of the formation of alkylsilane SAMs on the friction between the sliding contacts has been evaluated in two different methods. The first method was to test preformed SAM films under dry conditions, and the second was to premix one of the surfactants with Shell Vitrea ISO 32 mineral base oil and then spray the mixture to the contacts during the ball on disc testing. The test results show that an average of over 40 and 30% friction reduction was achieved for the hybrid contact when lubricated with the base oil mixed with OTS (>2··5 mM) and octadecyltrimethoxysilane (5 mM) respectively compared with that of the sliding contact lubricated by the base oil only. Since OTS may produce corrosive byproducts during SAM formation, octadecyltrimethoxysilane may be a more suitable additive for the hybrid contacts. 相似文献
5.
W. Hild S.I.‐U. Ahmed G. Hungenbach M. Scherge J.A. Schaefer 《Lubrication Science》2006,12(2):161-168
A comparative study of the microtribological properties of native oxide on Si (100), Si (100) coated with octadecyltrichlorosilane (OTS) and perfluorode‐cyltrichlorosilane (FDTS) self‐assembling monolayers (SAMs) is presented. The frictional properties between these samples and a bare silicon sphere were examined using a microtribometer. Microfriction was investigated as a function of the normal load and relative humidity. Also, the microfriction of OTS‐ and FDTS‐coated surfaces was studied as a function of sliding time and normal load to examine the lifetime of these monolayers. Confirming the results of earlier studies, in the microtribological regime OTS and FDTS significantly reduce the friction force in comparison to the bare, native oxide covered (hydrophilic) silicon surface. The friction vs. normal load curve of oxide‐covered surfaces as well as the SAMs can be described by contact mechanics. Lifetime measurements of the SAMs, examined as a function of the normal load and relative humidity, indicate that the OTS monolayers wear quickly in both dry and moist environments, while the lifetime of FDTS monolayers appears to increase in moist environments. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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7.
Patton Steven T. Cowan William D. Eapen Kalathil C. Zabinski Jeffrey S. 《Tribology Letters》2001,9(3-4):199-209
The effect of surface chemistry on the tribological performance and reliability of a MEMS lateral output motor is reported. Relative humidity (RH) and octadecyltrichlorosilane (OTS) self-assembled monolayer (SAM) coatings were used to change surface chemistry. Electrical and tribological performance of uncoated and OTS-coated motors were found to be dependent on RH. For uncoated motors, excessive wear of sliding contacts and welding (permanent adhesion) of static contacts were observed at 0.1% RH. Degradation of electrostatic force and high static friction (stiction) forces limited dynamic performance and reliability and caused device sticking at and above 70% RH. Around 50% RH, uncoated motors exhibited negligible wear, low adhesion, and a wear life at least three orders of magnitude longer than in the dry environment (experiments were stopped without failure after about one billion cycles). Water vapor behaved as a gas phase replenishable lubricant by providing a protective adsorbed film. The OTS coating broadened the operating envelope to 30–50% RH and reduced stiction, which allowed better dynamic performance at high RH. The OTS coating improved durability at 0.1% RH, but it was still poor. At high RH, stiction problems reoccurred when the OTS coating was worn away. By controlling and balancing surface chemistry (adsorbed water and OTS), excellent performance, low friction and wear, and excellent durability were attained with the lateral output motor. 相似文献
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9.
基于遗传算法的微机械陀螺的多学科设计优化 总被引:1,自引:1,他引:1
基于micro-electro-mechanical system(MEMS)技术的微机械陀螺是集传感器、致动器、检测与控制等于一体的复杂多学科交叉系统,其整体特性是各个子系统综合作用的结果。在充分考虑工艺、结构、电路、工作环境等多学科或因素的约束条件下,提出微机械陀螺的多学科概念设计模型。以陀螺的灵敏度最大为优化目标,利用遗传算法对设计模型进行全局优化,获得初步的最优设计方案,并采用有限元软件ANSYS验证优化结果的正确性。 相似文献
10.
This paper investigates the influence of the applied load and sliding velocity on the microfrictional properties of native
oxide-covered Si(100) and Si(100) coated with octadecyltrichlorosilane (OTS) and perfluorodecyltrichlorosilane (FDTS) self-assembled
monolayers (SAMs) using a precision microtribometer. Microfriction was investigated as a function of the applied load and
sliding velocity. As has been confirmed in earlier studies, in the microtribological regime, OTS and FDTS significantly reduce
the friction force in comparison to the bare native oxide-covered (hydrophilic) silicon surface. The friction versus applied
load curve of the substrate material as well as the SAMs-covered surfaces can be described by a model based on contact mechanics.
For the native oxide surface, microfriction is reduced with increasing sliding speed. The friction force of the OTS- and FDTS-covered
surfaces increases with load and is proportional to the natural logarithm of sliding speed. The increase with sliding velocity
gets larger for higher normal loads. It can be shown that this increase is proportional to the contact area of the counter
sample with the SAMs. 相似文献
11.
Microtribological properties of Langmuir–Blodgett (LB) films transferred from behenic acid (BehA), 2,4-heneicosanedione (HD) and its copper complex ((HD)2Cu) onto silicon surface were examined. To better understand the wear resistance performance of these LB monolayers, a comparison was made with a chemically grafted octadecyltrichlorosilane (OTS) monolayer. Auger electron spectroscopy (AES) was used for identification of the chemical composition of the monolayers, worn areas and counterpart surfaces. We observed that the studied LB films in microscale sliding contact exhibited stable friction properties comparable to OTS, and better wear performance than OTS at high contact pressure. The tribological properties of these LB monolayers were explained in terms of molecular packing density and molecular transfer to the counterpart surface. The relationship between the wear resistance of the studied LB films and the degree of molecular packing of the surfactants indicated that the wear properties of the LB films are strongly associated with the degree of molecular packing. We suggest that the steady low friction and high wear resistance of the BehA monolayer may partly be attributed to the transfer of the amphiphilic molecules to the counterpart surface in the contact region. 相似文献
12.
Sung PB Chang 《Journal of Mechanical Science and Technology》2006,20(4):554-560
This paper describes the demonstration of successful fabrication and initial characterization of micromachined pressure sensors
and micromachined jets (microjets) fabricated for use in macro flow control and other applications. In this work, the microfabrication
technology was investigated to create a micromachined fluidic control system with a goal of application in practical fluids
problems, such as UAV (Unmanned Aerial Vehicle) -scale aerodynamic control. Approaches of this work include: (1) the development
of suitable micromachined synthetic jets (microjets) as actuators, which obviate the need to physically extend micromachined
structures into an external flow; and (2) a non-silicon alternative micromachining fabrication technology based on metallic
substrates and lamination (in addition to traditional MEMS technologies) which will allow the realization of larger scale,
more robust structures and larger array active areas for fluidic systems. As an initial study, an array of MEMS pressure sensors
and an array of MEMS modulators for orifice-based control of microjets have been fabricated, and characterized. Both pressure
sensors and modulators have been built using stainless steel as a substrate and a combination of lamination and traditional
micromachining processes as fabrication technologies. 相似文献
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Silicon micromachines in microelectromechanical systems (MEMS) are coated with self-assembled monolayers (SAMs) in order to reduce the wear and stiction that are commonplace during operation. Recently, perfluorinated SAMs have been the focus of attention because they have better processing properties than hydrocarbon SAMs. In this study, we perform molecular dynamics simulations that model adhesive contact and friction for perfluorinated alkylsilane (Si(OH)3(CF2)10CF3) self-assembled monolayers (SAMs), which are commonly used in MEMS devices. Amorphous silica is used as the substrate for the SAMs in the simulations. The frictional behavior is investigated as a function of applied pressure (50 MPa–1 GPa) for a shear velocity of 2 m/s and compared to recent simulation results of hydrocarbon alkylsilane SAMs. The microscopic friction coefficient for the perfluorinated SAMs is the same as was measured for the hydrocarbon SAMs, but the shear stress is slightly larger than in the case of the hydrocarbon SAMs on amorphous silica. 相似文献
15.
Ian Laboriante Maxwell Fisch Amir Payamipour Fang Liu Carlo Carraro Roya Maboudian 《Tribology Letters》2011,44(1):13-17
The evolution of morphology, electrical properties, and chemical composition has been studied in cyclically contacting polycrystalline
silicon (polysilicon) surfaces coated with perfluoroalkylsilane self-assembled monolayer (SAM). The microinstrument used is
a MEMS cantilever that is repeatedly actuated out-of-plane to impact a landing pad and is then moved in-plane to enable nondestructive
in situ inspection of the impacted area. Analyses show that a device with a monolayer coating exhibits signs of surface degradation
after a much higher number of cycles than its uncoated counterpart. A sharp increase in contact resistance between the cantilever
and landing pad is observed at ~10 billion cycles for a coated device, versus ~25 million cycles for an uncoated device. Likewise,
the onset of grain fracture in the landing pad occurs at ~25 billion cycles for the SAM-coated device, versus ~3 billion cycles
for its uncoated counterpart. The effectiveness of the monolayer coating diminishes after more than 100 billion contact cycles
as the SAM layer is removed, and the polysilicon substrate becomes susceptible to adhesive wear. 相似文献
16.
In-situ vapor-phase lubrication of sidewall MicroElectroMechanical System (MEMS) devices is investigated with 1-pentanol vapor.
The 1-pentanol vapor successfully maintains lubricating properties between silicon contacts of MEMS devices. This is attributed
to the ability of alcohol to adsorb on the silicon surface and sustain a lubricating layer, which prevents wear of the MEMS
surfaces and minimizes friction. In the presence of these vapors, MEMS devices with sliding contacts operated without failure for up to a factor of 1.7 × 104 longer than in dry N2 gas alone, representing a dramatic improvement in operating life. Adhesion and friction were also investigated as a function
of alcohol vapor pressure. The adhesive force between microfabricated MEMS sidewall surfaces increases from ∼30 to ∼60 nN
as the alcohol vapor pressure is increased from 0 to 20% of saturation, and then only slightly increases to ∼75 nN at 95%
of saturation vapor pressure. This increase in force is well within the capabilities of even the lowest force on-chip actuators,
such as electrostatic comb drives which can typically generate a few μN of force. The static friction force was found to be
independent of alcohol vapor pressure within the uncertainties in the measurement. 相似文献
17.
The tribological properties of alkoxyl monolayers on oxide terminated silicon surfaces have been investigated using interfacial force microscopy. For a C18 alkoxyl monolayer, both adhesion and frictional properties are similar to those of a self-assembled monolayer of octadecanethiol on gold. Friction is shown to increase as the alkyl chain length of the molecules decreases. Analysis using contact mechanics models has been carried out to estimate reduced modulus, adhesion energy, and friction shear strength. These interfacial mechanical properties are correlated to molecular structures at the interface. 相似文献
18.
《Wear》2002,252(11-12):946-955
A polymer trilayer (sandwiched) film with a thickness of 20–30 nm has been designed to serve as a wear resistant nanoscale coating for silicon surfaces. These surface structures are formed by a multiple grafting technique applied to self-assembled monolayers (SAM) and functionalized tri-block copolymer, followed by the photopolymerization of a topmost polymer layer. The unique design of this layer includes a hard-soft-hard nanoscale architecture with a compliant rubber interlayer mediating localized stresses transferred through the topmost hard layer. This architecture provides a non-linear mechanical response under a normal compression stress and allows additional dissipation of mechanical energy via the highly elastic rubber interlayer. At modest loads, this coating shows friction coefficient against hard steel below 0.06, which is lower than that for a classic molecular lubricant, alkylsilane SAM. At the highest pressure tested in this work, 1.2 GPa, the sandwiched coating possesses four times higher wear resistance than the SAM coating. The wear mechanism for this coating is stress and temperature induced oxidation in the contact area followed by severe plowing wear. 相似文献
19.
传统的流体传感器由于存在着灵敏度低、体积大、成本高等缺点,而且微流体与宏观流体流动特性不同,所以其在微流体的流体特性测量中存在很大的局限性。随着MEMS技术的发展,硅微机械流体传感器的出现克服了传统流体传感器的缺点。硅微机械流体传感器已成为MEMS的研究热点之一。按其用途进行了分类,着重介绍了流体压力传感器、流量传感器和表层摩擦力传感器。分别从各种传感器的基本原理、性能、应用范围、优缺点及其所能达到的技术指标方面进行了描述。基于MEMS的硅微机械流体传感器具有广阔的前景。 相似文献
20.
多晶硅表面微机械光学角速率传感器 总被引:1,自引:0,他引:1
多晶硅表面微机械技术是微机电系统(Microeletromechanical Systems,MEMS)中重要的加工技术。本文采用这种加工技术,提出了一种基于Sagnac效应的新型微机械学光角速率传感器(Optical Rotation Sensor,(ORS)。由于采用MEMS的最新技术,安将是一种低成本、微型化的ORS,文中给出了ORS中环形谐振腔的设计和基本理论分析,并提出了电路和控制系统的 相似文献