外啮合齿轮泵内部两相流动的数值模拟

应用动网格和气穴模型,对某外啮合齿轮泵进行三维数值模拟研究,分析齿轮泵的总体性能和内部流场特性,得出齿轮泵流量随进口压力减小的变化规律,模拟其内部气穴的产生、运输以及破灭过程。计算结果表明,在齿轮泵的工作过程中啮合处会产生气穴。若泵进口腔的压力较高,气穴就会随着工作液的填充而迅速消失,齿谷输送的工作液中不会包含气穴,齿轮泵的流量只会随进口压力的降低略微下降;若泵进口腔的压力过低,气穴不但难以消失,而且还会被齿谷输送走,导致齿轮泵质量流量迅速下降。齿轮泵进口压力越低,则输送的工作液中气体所占的比体积越高,质量流量下降越明显。     

Fabrication and characterization of thermally actuated bimorph probe for living cell measurements with experimental and numerical analysis

This paper deals with a novel structure for single-cell characterization which makes use of bimorph micro thermal actuators combined with electrical sensor device and integrated microfluidic channel. The goal for this device is to capture and characterize individual biocell. Quantitative and qualitative characteristics of bimorph thermal actuator were analyzed with finite element analysis methods. Furthermore, optimization for the dimension of cantilevers and integrated parallel probe systems with microfluidic channels is able to be realized through the virtual simulation for actuation and the practical fabrication of prototype of probes. The experimental value of probe deflection was in accordance with the simulated one.     

Pressure response and droplet ejection of a piezoelectric inkjet printhead

The present study aims to investigate the pressure rise in the ink flow channel and the ink droplet formation process of a piezoelectric printhead after an electrical pulse is applied to the printhead. The ink flow channel is modeled as a straight circular pipe followed by a convergent nozzle. Both numerical analysis and experimental observations are performed in this study. In the numerical analysis, a characteristic method is used to solve the one-dimensional wave equation to obtain the transient pressure and velocity variations in the flow channel of the printhead. In this analysis, the channel is assumed to have a non-uniform cross section. In addition, a flow visualization system was set up to observe the ink droplet injection process. After the piezoelectric material is driven by the input electric pulse, the ink droplet images are immediately captured by a charge-couple device (CCD) camera converted to a digital image via a frame grabber, and stored in a computer. The results obtained from the experimental observations are also compared with the numerical prediction. The effects of electric pulse shape and voltage on the ink injection length and the ejected droplet weight are also presented.     

双稳态膜片的有限元分析与实验研究

双稳态结构是降低微流体器件功耗的有效手段,使膜片获得双稳态结构往往需要对材料进行热处理。文中提出了一种不需要进行材料热处理,通过将圆形膜嵌入半径相对较小的圆形槽从而使膜片达到双稳态效果的方法。基于聚丙烯材料,对设计和制作的双稳态结构的初始挠度、开关压强及密封能力进行了有限元分析。结果显示,当槽半径为19.75 mm,膜片半径较槽半径大100μm时,膜片能够在其中心半径为0.5 mm的区域密封600 kPa以上的入口压力,而膜片的开关压强约为5.2 kPa。通过实验测量了膜片中心变形随压强的变化及实际开关压强的大小,实验结果与仿真结果吻合较好。最后就结构制造精度对初始挠度、开关压强及密封压强的影响进行了分析。     

A complementary-metal-oxide-semiconductor-field-effect-transistor-compatible atomic force microscopy tip fabrication process and integrated atomic force microscopy cantilevers fabricated with this process

A complementary-metal-oxide-semiconductor-field-effect-transistor-compatible process for the fabrication of atomic force microscopy cantilevers with integrated tips has been developed. For the first time, the tips are fabricated after the completion of the regular complementary metal-oxide-semiconductor-field-effect-transistor fabrication process sequence. On-chip circuit components, such as piezoresistive deflection sensors, deflection actuators, and amplifiers, are fabricated on the mirror-polished surface of the wafer, ensuring optimal performance. The tip fabrication process is based on anisotropic silicon etching at low temperature using a tetramethylammonium hydroxide solution. The anisotropic etching process has been optimized to ensure process controllability. Using the described process, complementary-metal-oxide-semiconductor-field-effect-transistor-based cantilevers with piezoresistive deflection sensors and integrated tips have been successfully fabricated. Force-distance curves and scanning images in constant-force mode have been recorded.     

Quantum size aspects of the piezoresistive effect in ultra thin piezoresistors

Proximal probe sensors with an ability to detect extremely small forces (10(-15)-10(-18)N) play significant role in scanning probe microscopy applications. The detection of extremely low forces, require producing micromachined cantilevers with as small as possible spring constants, which is considered by the optimization of the sensor design. In the last year many papers describing the fabrication process of producing ultrathin cantilevers (below 100nm) with integrated piezoresistors for deflection read-out have been published. In the case of such cantilevers the required thickness of piezoresistors is in the range of 50nm. From a quantum mechanical point of view, an electrical carrier transport confinement in direction perpendicular to the cantilever surface can be expected and in this manner we have to consider the quantum size effect.The goal of the project described in this paper is to calculate and determine the piezoresistive coefficients in p type Si thin (under 50nm) piezoresistors taking into account the quantum size effect and to compare them with the corresponding coefficients for bulk material. The calculation of the band structure will use the mathematical apparatus of an exact analytical diagonalization six-band k.p model, modified with the envelope function approximation.The behaviour of the thin piezoresistors employed as integrated deflection read-out will be also discussed. Moreover, critical issues in the realization of piezoresistors formed by MOS transistor channel will be presented.     

Prediction of transient lubricating oil flows within the connecting-rod of a diesel engine

This paper develops Aa computer program for the unsteady flow analysis of diesel engine lubrication systems. The possibility of cavitations developing in the big-end bearing groove due to the reciprocating motion of the connecting rod is investigated at the designed running speeds. The flow passage geometry especially the head loss coefficients of the bearing grooves s affects the minimum values of the head and the point when the development of the cavitations is initiated As the loss coefficient at the big-end increases and that of the small-end decreases, then the cavitations can be initiated. An orifice can be used to suppress the development of the cavitations and the diameter ratio and the location needs to be carefully selected to avoid unnecessary pressure loss. The channel size in the connecting rod is also an important parameter for optimization of the overall lubrication system; as the pipe diameter decreases, the minimum head increases and suppresses the cavitations from developing The minimum head always appears at the trailing groove of the big-end bearing.     

基于气动微流控芯片的新型智能痕量灌溉系统动态流量特性研究

提出一种基于气动微流控芯片的新型智能痕量灌溉系统，利用气动微流控芯片片上膜阀作为控水元件,阐述了新型智能痕量灌溉系统和片上膜阀的结构设计和工作原理，建立了新型智能痕量灌溉系统和片上膜阀的物理模型。对单个片上膜阀不同气体驱动压力、不同液流驱动压力下的出口流量，以及片上膜阀不同组合时的动态流量特性进行仿真分析，给出了不同情况下智能痕量灌溉系统出口流量和出口截面流速、压力分布等特性的分析结果。利用PDMS材料和软刻蚀技术对痕量灌溉系统控水元件进行封装，并对其流量特性进行了实验研究。讨论了在液流驱动压力为10 kPa、不同气体驱动压力时和气体驱动压力为0、不同液流驱动压力时，影响痕量灌溉系统流量的几种因素，并对实验现象进行理论分析。     

Design of a nano-printer based on AFPN (Active Fountain Pen Nano-lithography) using switch control

In this paper, the design and the construction analysis of an innovative nano-printer system are presented. A nano-printer system is comprised of automatic transmission parts and modified Active Fountain Pen Nano-lithography (AFPN) device. The patterning is made by a switch control method. For accurate control and fabrication of this device, the fluidic system is simplified by embedding a PZT (Lead Zirconate Titanate) plate in the nano-printer. And, without the cantilevers connecting the reservoir and tip, less energy loss is induced and the whole device becomes more sophisticated. In this paper, the critical channel size is decided for the whole simulation, and then the mechanical and piezoelectric properties of PZT are analyzed by the commercial software, ANSYS. The deformation of the PZT can be controlled precisely. Based on the analysis of the fluidic dynamics of this system, the line width of the pattern was found to depend on the mass of the meniscus formed at the tip. As long as the initial mass of the meniscus is set, the maximum patterning speed can be determined as well. Consequently the printing velocity of this system can be increased considerably beyond that of DPN (Dip-Pen Nano-lithography) or FPN (Fountain Pen Nano-lithography) because the mass of meniscus can be controlled by the applied voltage.     

Dynamic plastic behavior of a free–free beam striking the mid-span of a clamped beam with shear and membrane effects considered

Recently Yu et al. (Int. J. Solids Struct. 38 (2001) 261) made a study on the dynamic behavior of a flying free–free beam striking the tip of a cantilever beam using the rigid, perfectly plastic (r-p-p) material model. Later, also based on the r-p-p material model Yang and Yu (Mech. Struct. Mach. 29 (2001) 391) analyzed another impact problem of a free rotating hinge beam striking a cantilever beam. Both of these studies ignored the finite deflection effects on the plastic behavior of the colliding beams. However if the free–free beam strikes a clamped beam, the influence of finite-deflections, or, geometric changes, must be retained in the governing equation if the maximum permanent transverse displacement of the clamped beam exceeds the corresponding beam thickness. The problem becomes more interesting since the deformation mechanisms of the beam system and the partitioning of energy dissipation in the beams are significantly different from those predicted by ignoring the influence of membrane forces. Accordingly the failure modes of the structure are different.In the present paper, a theoretical model based on the r-p-p material idealization is proposed to simulate the dynamic behavior when the mid-point of a translating free–free beam impinging on the mid-span of a clamped beam with the beam axes perpendicular to each other. The plastic behavior of the beam system is explored with shear sliding and finite deflection effects taken into account. The final deflection, the dissipation of energy within the two beams after impact and the influence of the structural and material parameters are discussed. It is shown that membrane force plays an important role during the response process, especially when the deflection is of the same order as the thickness of the clamped beam.     

一种硅微压阻式压力传感器的研究

研究了一种量程为20kPa的压阻式微压力传感器,同时采用ANSYS仿真得出影响传感器性能的一些规律。应用小挠度理论设计计算了压阻式硅传感器方形弹性膜片结构,并对圆形膜片与方形膜片进行了比较,同时设计了硅芯片以及压敏电阻的尺寸和阻值。通过模型分析和对方型硅膜片的模拟计算,确定了压敏电阻最佳放置位置,来提高灵敏度;并在各个不同的压力下仿真出应力分布图、得出输入—输出关系图及应力峰值。研究为压阻式微压力传感器的结构以及优化、稳健设计提供了一定参考。     

Feasibility of tunable MEMS photonic crystal devices

Periodic photonic crystal structures channel electromagnetic waves much as semiconductors/quantum wells channel electrons. Photonic bandgap crystals (PBC) are fabricated by arranging sub-wavelength alternating materials with high and low dielectric constants to produce a desired effective bandgap. Photons with energy within this bandgap cannot propagate through the structure. This property has made these structures useful for microwave applications such as frequency-selective surfaces, narrowband filters, and antenna substrates when the dimensions are on the order of millimeters. They are also potentially very useful, albeit much more difficult to fabricate, in the visible/near-infrared region for various applications when the smallest dimensions are at the edge of current micro-lithography fabrication tools. We micro-fabricated suspended free standing micro-structure bridge waveguides to serve as substrates for PBC features. These micro-bridges were fabricated onto commercial silicon-on-insulator wafers. Nanoscale periodic features were fabricated onto these micro-structure bridges to form a tunable system. When this combined structure is perturbed, such as mechanical deflection of the suspended composite structure at resonance, there can be a realtime shift in the material effective bandgap due to slight geometric alterations due to the induced mechanical stress. Extremely high resonance frequencies/device speeds are possible with these very small dimension MEMS.     

纳米硬度计研究多晶硅微悬臂梁的弹性模量

利用纳米硬度计通过微悬臂梁的弯曲试验来测量其力学特性是一种简便而有效的方法,具有很高的载荷分辨率,可精确测量微悬臂梁纳米级弯曲形变。运用该方法在研究微悬臂梁的弯曲形变过程中,必须考虑压头在微悬臂梁上的压入以及微悬臂沿宽度方向的挠曲。微悬臂梁采用普通的集成电路工艺(IC)制造。试验研究表明,多晶硅微悬臂梁的纯挠曲与载荷成很好的线性关系,呈现弹性变形,通过该线性关系可计算得到梁的弹性模量。测得的多晶硅微悬臂梁的弹性模量为156±(2.9%-6.3%)GPa。     

Study on the web deformation in ink transfer process for R2R printing application

Web deformation occurring in the ink transfer process from the printing roller to the flexible web was investigated using a CFD technique for the application in roll-to-roll printed electronics. Analysis for the flow-structure interaction was conducted to assess the deflection and stress distributions of the web. To make the present analysis more relevant to the real printing system, both realistic geometric configuration and ink properties were set up using the information obtained from the typical roll-to-roll system. Fluid properties were found to influence to the shape of the transferred ink and the web deformation. As the line width becomes smaller than 100 microns, the appreciable distortion in the shape of the transferred ink occurred due to a relative importance of surface tension. Non-negligible web deflection occurs in all the cavity geometries considered in the present work but the ratio of the web deflection to the line width gets smaller as the printing pattern width becomes smaller. Thus, the surface and deflection will be important factors for the better printing quality under the 100 micron range.     

射频识别标签天线的按需微喷射制备

基于数字化微喷射技术搭建了射频识别(RFID)标签天线的按需微喷射制备系统。首先,将纳米银导电墨水按需微喷射到镀有疏水化薄膜的聚对苯二甲酸乙二醇脂(PET)基底表面形成天线图形;然后在恒温干燥箱内烧结,形成RFID标签天线。实验研究了微喷射系统参量对液滴产生的影响以及制备参数对纳米银导线成线的影响,制得了最小线宽为100μm、厚度为2.8μm、电阻率为5.2μΩ·cm且阻值具有较好线性度的导线。设计、仿真和制备了弯折偶极子天线,并对其性能参数进行了测试,结果显示其天线谐振频率、带宽和谐振点S11参数等与仿真结果具有较好的一致性。实验结果表明,按需微喷射导电银墨水制备RFID标签天线的方法具有系统结构简单、成本较低、液滴微喷射精确、便于制备任意天线图形等特点;制备的弯折偶极子天线尺寸可控、导电性高、阻值均一性好,并具有较好的天线性能。     

Design and fabrication of a micro PZT cantilever array actuator for applications in fluidic systems

In this article, a micro cantilever array actuated byPZT films is designed and fabricated for micro fluidic systems. The design features for maximizing tip deflections and minimizing fluid leakage are described. The governing equation of the composite PZT cantilever is derived and the actuating behavior predicted. The calculated value of the tip deflection was 15 μm at 5 V. The fabrication process from SIMOX (Separation by oxygen ion implantation) wafer is presented in detail with the PZT film deposition process. The PZT films are characterized by investigating the ferroelectric properties, dielectric constant, and dielectric loss. Tip deflections of 12 μm at 5 V are measured, which agreed well with the predicted value. The 18 μ1/s leakage rate of air was observed at a pressure difference of 1000 Pa. Micro cooler is introduced, and its possible application to micro compressor is discussed.     

An approach to design and fabrication of a piezo-actuated microdroplet generator

In this research, a piezo-actuated microdroplet printing device for drop on demand (DOD) is studied. Microdroplet devices are used in applications such as inkjet printing, rapid prototyping, and production of metal powder. An experimental device is designed and manufactured, in which the fluctuation of a flexible diaphragm–by a piezoelectric element–pushes the liquid out of the nozzle and produces droplets. The deflection of diaphragm due to different voltages is investigated by analytical and experimental study. In experiments, beside deflection voltage, the effect of suction and compression time and nozzle diameter on droplet size, droplet velocity, satellite droplets, and cutoff length is also investigated. High-speed camera is used to take photo of the formation of droplets. In order to calculate droplet diameter and velocity, outputs of high-speed camera are processed by MATLAB R2008a. Results obtained by analytical and experimental are in good agreement with each other and could be used to control droplet properties. It is shown that the device is able to produce droplet of diameter from 450 to 1,000 μm. Velocity of droplet can be also controlled in a range of about 0.2 to 1.4 m/s. The repeatability is investigated by ink printing on a paper attached to a rotary table.     

Fabrication of low-cost polydimethylsiloxane master from laminating foil for isotachophoresis separation on a chip

This article introduces use of laminating foils as the base for rapid polydimethylsiloxane master fabrication. The designs are punched directly to the foil structure with fabricated knife; therefore, the preparation time requires only a few minutes. This approach offers low-cost and variable possibility of master fabrication to produce microfluidic devices the size of dozens of microns. The resulting structures enable precise control of various device geometries, such as variable channel diameters and shapes in a single device. We describe the fabrication of microfluidic channels using these masters with polydimethylsiloxane polymer. The usability is demonstrated for the isotachophoretic separation of organic anionic dyes.     

The mechanism of metal removal by an abrasive tool

To study the basic mechanism of metal removal with abrasive tools, the cutting action of a simulated tool was arrested by a quick stop device. The material behavior ahead of the tool face during cutting was observed by examining the cross section along the cutting groove microscopically. Variation of the stagnant region during the metal removal process was observed. It was found that the initial position of the stagnant tip determined whether or not chips were produced and the chip size.     

液态金属电子墨水与印刷基底之间的撞击作用机理研究

液态金属印刷电子学是正在兴起的学科前沿,其利用室温液态金属代替传统电子墨水在基底上直接写出电子电路,具有独特的快捷、低成本优势。本文首次研究了制约此类电子印刷质量的一个关键问题,即液态金属墨水与印刷基底材料之间的撞击作用机理。通过实验评估了氧化效应对液态金属液滴对几类典型基底界面(打印纸、硅胶板和橡胶板)的碰撞特性的影响,对比研究了基底材料、液滴碰撞速度、液滴尺寸等的影响规律,并通过理论模型解释了液态金属与不同基底之间的粘附性差异机理。研究结果对于今后筛选理想的印刷材料及提升液态金属电子打印质量有重要意义。