bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Dynamics Simulations of Interfacial Heat and Mass Transfer at Nanostructured Surface
Authors: Nagayama Gyoko , Kawagoe Masako , Tsuruta Takaharu
Published: June 2009

The nanoscale heat and mass transport phenomena play important roles on the applications of nanotechnologies with great attention to its differences from the continuum mechanics. In this paper, the breakdown of the continuum assumption for nanoscale flows has been verified based on the molecular dynamics simulations and the heat transfer mechanism at the nanostructured solid-liquid interface in the nanochannels is studied from the microscopic point of view. Simple Lennard-Jones (LJ) fluids are simulated for thermal energy transfer in a nanochannel using nonequilibrium molecular dynamics techniques. Multi-layers of platinum atoms are utilized to simulate the solid walls with arranged nanostructures and argon atoms are employed as the LJ fluid. The results show that the interface structure (i.e. the solid-like structure formed by the adsorption layers of liquid molecules) between solid and liquid are affected by the nanostructures. It is found that the hydrodynamic resistance and thermal resistance dependents on the surface wettability and for the nanoscale heat and fluid flows, the interface resistance cannot be neglected but can be reduced by the nanostructures. For the hydrodynamic boundary condition at the solid-liquid interface, the no-slip boundary condition holds good at the super-hydrophilic surface with large hydrodynamic resistance. However, apparent slip is observed at the low hydrodynamic resistance surface when the driving force overcomes the interfacial resistance. For the thermal boundary condition, it is found that the thermal resistance at the interface depends on the interface wettability and the hydrophilic surface has lower thermal resistance than that of the hydrophobic surfaces. The interface thermal resistance decreases at the nanostructed surface and significant heat transfer enhancement has been achieved at the hydrophilic nanostructured surfaces. Although the surface with nanostrutures has larger surface area than the flat surface, the rate of heat flux increase caused by the nanostructures is remarkable.
Process Monitoring in Automatic Assembly of Minilenses With Fiberscopes
Authors: Lan Tian , Chen Siying , Ni Guoqiang
Published: June 2009

In this paper, we present experimental results of process monitoring and process control in automatic assembly of minilenses in front of a miniature flexible fiberscope. For the purpose of process visualization and process control, an LED light source, a grating and a micrometer screw are compacted together in a vacuum gripper. A positioning system, a fiber chuck, a mimilens magazine and a fiberscope have been installed in the system and an image processing algorithm for process control has been developed. The optical design and assembly process are presented here in details. The projection of an illuminated grating through the minilens on the fiberscope is used to position the minilens automatically by an image processing unit and the motion system. The position system has a minimum step size of 5 μm in translation and 0.01° by rotation. The repeatability of the translation stages is about ±2.5 μm. It is shown from the experimental results that the tilt axial angle between the optical axis of the minilens and the geometrical axis of the fiberscope is less than 4°.
Numerical Simulation Method of Microstructure and Optical Characteristics of Magnetic Fluids
Authors: Xuan Yimin , Li Qiang , Li Bing
Published: June 2009

A magnetic fluid possesses a variety of unique characteristics because of both the magnetism of nanoparticles material and the fluidity of the carrier liquid. The characteristics of magnetic fluid depend upon the microstructure of the magnetic nanoparticles aggregation. This paper aims to use the molecular dynamic method to simulate the microstructure formation in a magnetic fluid. A number of inner and external potentials and forces acting on the magnetic fluid are included to reveal the effects of these potentials and forces to the magnetic fluid morphology. Further, a numerical method to study the optical feature of the magnetic fluid films is developed with the Monte Carlo method based on the simulated microstructures, which tracks the spread process of ray transmitting through the magnetic fluid film and computes the spectral transmittivity of the magnetic film. Some factors of affecting the spectral transmittivity of magnetic fluid film are investigated, such as the film thickness, the concentration and diameter of magnetic nanoparticles, and strength of externally applied magnetic field. By combining the molecular dynamic simulation and the ray-tracing method, this paper provides a useful tool for investigating the morphology and optical characteristic of a ferrofluid film.
Molecular Dynamics Simulation of Water Behavior as a Function of Temperatures and Monomer Numbers in Nafion 117
Authors: Oh Kyung Su , Park Seungho , Kwon Ohmyoung , Choi Young Ki , Lee Joon Sik
Published: June 2009

The proton exchange membrane plays a critical role as an electrolyte for proton transports in the PEMFC. Generally, the membrane, such as Nafion 117, consists of a polytetrafluoro-ethylene (PTFE) backbone and side-chains terminated with a sulfonate group (SO3−). Operating the fuel cell, the membrane preferentially becomes hydrated by absorbing water. Then, the hydrogen atom on the SO3− part of the side-chain can detach from its own position and hop to the next SO3− site. The water management is the key to the efficient operation of the fuel cell, since the water content is the one of decisive factors for membrane’s lifetime and efficient operations of fuel cells as well. In this report, we set up the molecular model for hydrated Nafion 117 and simulate the molecular movements for various temperatures and monomer numbers. Here, we obtain the mean square displacements of water molecules and estimate the self-diffusion coefficients of water in the Nafion 117.
Design and Simulation of Novel MEMS Optical Acceleration Sensor
Authors: Jia Shuhai , Kong Weijun , Yang Jia , Li Yigui
Published: June 2009

A novel MEMS optical acceleration sensor based on a Fresnel diffraction micro-lens is designed in this paper, which is suitable to be used in the fly-by-light system of aviation. The principle of sensor is described. The dynamic performance design of sensor is presented. The constant of silicon micro spring and natural frequency is calculated by using the numerical simulator (ANSYS 8.0) of finite element method. Because the design of the sensor integrates a Fresnel diffraction lens, the optical throughput is high, which brings the advantage of higher signal-to-noise ratio with respect to photon noise. The design of the sensor is well suitable for mass production with normal process of MEMS a low cost. The proof-of-Principle fabrication and experiments show that the principle of this new MEMS optical acceleration sensor is correct.
Design, Synthesis, and Performance of a Carbon Nanotube/Metal Foil Thermal Interface Material
Authors: Cola Baratunde A. , Xu Xianfan , Fisher Timothy S.
Published: June 2009

The thermal performance of an interface material comprised of a metal foil with dense, vertically oriented carbon nanotube (CNT) arrays synthesized on both of its surfaces is characterized for rough and smooth interfaces. The CNT/foil deforms in the interfaces by two mechanisms, CNT deformation and foil deformation, that may significantly increase the number of CNT contact spots on both sides of the foil. As a result, the thermal conduction at the CNT-array-free-tip interfaces is greatly increased from previous measurements.
An Instrument for Measuring Mechanical Properties of MEMS Materials by Nanoindentation and Micro-Beam-Bending
Authors: Wang Hairong , Zhao Zexiang , Jiang Zhuangde , Du R.
Published: June 2009

This paper presents an instrument for measuring the mechanical properties of MEMS materials by both nanoindentation and micro-beam-bending tests. The nanoindentation test requires high resolution within a very small displacement range, whereas the micro-beam-bending test needs relatively large displacement range but lower resolution. Though, for both tests, loading with small increment is necessary. In order to satisfy different requirements and yet save cost, a two-stage system driven by a PZT actuator in the first stage and by a DC-Mike Linear motor in the second stage is designed and built. The instrument achieves a displacement resolution better than 1 nm within a range of 50 microns in the first stage and the maximum output displacement is over 1 mm in the second stage. The measurement accuracy is validated through experiments.
Plasma Deposition of Nanometre Thin Coatings Displaying Super Hydrophobic and Oleophobic Properties
Authors: Coulson Stephen
Published: June 2009

P2i’s plasma process allows the attachment of ultra-low surface energy coatings, one third that of PTFE, to a wide range of substrates, including, glass, metals and polymers. This gas phase process can penetrate complex structures with nano and micro features to form well adhered nano thin films suitable for microfluidic devices. By using this technique multiple assays show comparable performance on miniaturization without the need for individual optimization.
Effects of Laser Fluence on Surface Nanostructuring With a Laser-Assisted Scanning Tunneling Microscope
Authors: Feng Xuhui , Wang Xinwei
Published: June 2009

In this work, molecular dynamics simulation is performed to explore the long-time (up to 5 ns) behavior of argon crystal in surface nanostructuring with a laser-assisted scanning tunneling microscope. The surface nanostructuring region is limited to tens of nanometers in diameter although the simulated systems are much larger (more than 300,000 of atoms inside). This study is focused on the long-time solidification and crystallization procedure, which is driven by the heat conduction in the material. The effect of the computational domain on the final nanostructuring result is studied in detail. Different laser fluences are used in the simulation to explore how and to what extent the energy input affects the dimension and profile of the surface nanostructure. Meanwhile, spot-like structural defects in the sub-surface region are investigated during the solidification. Additionally, the evolutions of surface melting depth and lowest position in the whole process reveal the impact of different laser fluence on surface nanostructuring from another aspect.
Applications of Micro-PIV Technique in Visualization of Flow in Microspace
Authors: Wang Ruijin , Lin Jianzhong , Wang Yifeng
Published: June 2009

A micro-resolution particle image velocimetry (micro-PIV) technique for flow visualization in microspace is presented here. The micro-PIV system was constructed through adding an epi-fluorescence microscope, improving the light source and choosing suitable tracing particle. According to smaller characteristic length of the flow in microscale and higher precision prolepsis, an image process technique based on cross correlation algorithm was conducted. To eliminate the main error caused by Brown motion of tracer particle, an approach by averaging the velocities of the ensemble particles in same interrogation plot was brought forward. Micro-PIV measure-ments of three typical flows (in a micromixer, near barriers and in a micro-jet) were carried out. The experimental results show that the micro-PIV system is suitable to both steady and unsteady flow in microscale. It is helpful to design micro-devices and analysis on data collected from such micro-devices.
Analysis on Chaotic Mixing Inside a Plug and Determination of Lagrangian Velocity
Authors: Wang Yifeng , Lin Jianzhong , Wang Ruijin
Published: June 2009

Mixing multiple fluids based on plugs flow is a better approach in microfluidic system. In order to understand the mixing mechanism based on plug flow, theoretical analysis based on chaotic mixing was carried out, and a micro-resolution particle image velocimetry (Micro-PIV) is used to measure the flow field in liquid plug involving liquid species to be mixed. Two recirculation flows forming in plugs can enhance the mixing efficiency because folding and stretching of the liquids occured deterministically in plugs. In addition, the Lagrangian velocity were determinated on the basis of Eulerian velocity by subtracting this droplet velocity vector from the measured Eulerian velocity field of the tracing particles results inside the moving droplet. These results are helpful to optimize the structure of micromixer and develop droplet based microfluidic system.
Study on the Friction and Wear Behavior of PEEK Composites Filled With Nanometer Compounds and PTFE
Authors: Peng Xu-Dong , Li Ji-Yun , Zeng Qun-Feng
Published: June 2009

The friction and wear behavior of polyetheretherketone (PEEK) composites was investigated, which are reinforced with nanometer Al2O3 or nanometer TiO2 and blended with polytetrafluoroethylene (PTFE) in a fixed weight fraction of 10% and are prepared by heat compression moulding. The studies emphasized particularly on the nanometer Al2O3 filled PEEK composites. The tests were performed on a pin-on-disc test apparatus with a PEEK composite pin sliding against AISI 1020 carbon steel disc under dry friction conditions and were all carried out at room temperature. The worn surfaces of the PEEK composites were examined by scanning electron microscopy (SEM). Results indicated that the above PEEK composites exhibited lower friction coefficient and wear rate in comparison with the mixture of PEEK with PTFE. The SEM micrographs of the worn surfaces indicated that the scratched and ploughed marks appeared on the wear scar of PEEK filled with PTFE, while the scuffing on the worn surfaces of nanometer Al2O3/PTFE/PEEK was obviously abated. The optimal content of nanometer Al2O3 in the filled PEEK composite should be recommended as 6.5 wt %. The friction behavior of the nanometer TiO2/PTFE/PEEK composites was far better than that of the nanometer Al2O3/PTFE/PEEK composites under the same test conditions and with the same content of nanometer compounds, which was perhaps due to much more strong synergistic effect between nanometer TiO2 and PTFE than that between nanometer Al2O3 and PTFE.
Effects of Surface Roughness and Slip Flow on the Performance of a Spiral Groove Gas Face Seal
Authors: Peng Xu-Dong , Sheng Song-En , Yin Xiao-Ni , Li Ji-Yun
Published: June 2009

Considering the effects of surface roughness and slip flow, the extended Reynolds equation presented by Makino et al [1] is used to set up the finite element model for a non-contact spiral groove dry gas face seal (S-DGS). The analyses for a typical S-DGS at low speed (≤ 500 rpm) and low pressure (≤ 0.606 MPa) showed that the effect of slip flow on the sealing performance is significant for 0.05≤ Kn < 1.0, where Kn refers to the Knudsen number, but the effect of surface roughness on the sealing performance varies with the different areas of both the two faces. When the standard deviation of composite roughness is less than 1.0 micron and in the range of 0.5≤ Kn≤ 1.0, the effects of surface roughness and slip flow diminished on gas film stiffness and frictional work but are still significant on the leakage rate. The effect of surface roughness of the spiral groove bottom is significant and should be considered, but the effects of the other surface roughness, i.e. the soft ring surface roughness and the un-grooved hard ring surface roughness, are negligible only when the value of the standard deviation of composite roughness meets with API standards.
Experimental Observation of Liquid Exploding Emission in Micro Tubes
Authors: Wu Di , Peng Xiao-Feng
Published: June 2009

In present paper, a high speed CCD was employed to conduct a visualized observation of the phenomena of nucleation in micro capillary tubes covered with transparent metal film on the tube serving as the heater. When the heat flux reached a certain value, the liquid in capillary tubes was emitted instantaneously, which is referred as liquid exploding emission here, rather than generating visible bubbles. The critical heat flux and tube inner temperature corresponding to this phenomenon were measured to discuss the fundamental characteristics and physical significance of the phenomenon in different capillary tubes having different tube length, heating length and diameters.
Transitional Boiling Characteristics of an Individual Liquid Droplet on the Heated Solid Surface
Authors: Gui Lu , Peng Xiao-Feng , Wang Xiao-Dong
Published: June 2009

An experimental investigation was conducted to visually observe the transitional boiling in an individual water droplet on heated solid surfaces, with temperature ranging from 120°C to 160°C. Using a high-speed video imaging system, the dynamical process of the evaporation and boiling behavior of a droplet was recorded. Infrared ray temperature measurement technique was employed to investigate the instantaneous characteristics of heat transfer as the droplet was boiled. In the transition boiling regime, the phase change behavior of a droplet displayed a cyclical process. Restricted cyclical, sole-bubble cyclical and metastable cyclical styles were observed as the surface temperature increased.
Nanoscale Energy Conversion and Its Applications
Authors: Hu Zhiyu
Published: June 2009

There are many ways in which the energy around us can be stored, converted, and developed for use. Energy exists in two basic types: potential energy, including chemical, elastic, gravitational, and nuclear energies, and kinetic energy, including heat, electrical, and electromagnetic energies. It is often necessary to convert one type of energy to another type or other types of energy. However, human engineering and nature take very different paths to complete such conversion processes. This paper discusses the similarities and dissimilarities of energy conversion processes that are taken by nature and human engineering. One might notice that energy conversion efficiency in biological systems is often higher than what human engineering can offer. As an attempt to mimic nature’s way of energy conversion on the nanoscale, our experiment indicates that nanocatalytic particles can convert chemical energy directly to thermal energy without conventional high-temperature gas-phase combustion and without the traditional ignition process. Furthermore, we have converted chemical energy to thermal energy and thermal energy to electrical energy on semiconductor materials, an achievement that raises the possibility of constructing a new class of nano-thermoelectric power generation systems.
Microstructure Enhanced Heat Exchanger for Pressurized Water Reactor
Authors: Lian Kun , Zhang Min , Li Guoqiang , Pang Su-Seng , Ling Zhong-Geng , Liu Chang-Geng , Ibekwe Samuel
Published: June 2009

The goal of this research is to enhance the heat exchanger efficiency of pressurized water reactor (PWR) by using LIGA or LIGA-like technique made microstructures. The heat transfer inside the boiler is a complex combination of different physical phenomena, which, besides the traditional convection, conduction, and radiation, includes liquid to vapor phase change, vapor nucleation and evolution, surface tension between the liquid and heating element, and so on. This paper presents the updated total heat transfer enhancement results of the boiling process by adding microstructures on the surface of the heating elements. Different types of microstructure configurations were tested. The power input, temperature of the heating element, and boiling phenomena were recorded. The behavior of increase in power versus rise in temperature of testing coupon is used to evaluate the heat transfer efficiency of the heating element. The steam generating efficiency at fixed input power and fixed temperature have been used to assess the performance of heating elements with different microstructure configurations. The preliminary results show that by simply adding micro-sized poles on the surface of the heating element, the power input can be increased almost 100% higher than that without poles on the surface at 360°C. The current results suggest that the main factors leading to the enhanced boiling process are the surface morphology and configuration of the microstructures. These provide enhanced vapor nucleation sites at heating surface, which result in a better vapor evolution processes, and yield a low superheat temperature. It ultimately results in a higher boiling heat transfer efficiency.
Preparation and Properties of Nano-Calcium Carbonate Modified PVC Using Ultrasonic Irradiation
Authors: Hu Shengfei , Chen Wen , Li Huaxing
Published: June 2009

PVC/nano-CaCO3 composites were prepared through ultrasonic irradiation. The optimum time of ultrasonic irradiation is 30 min. The fracture toughness of the nanocomposites was investigated by J-integral method based on the mechanical properties and morphology. Compared with corresponding nanocomposites and unfilled PVC, the prepared nanocomposites exhibit outstanding mechanical performances. The mechanical properties of spindly shaped CaCO3 filled PVC are better than these of the cubic nano-CaCO3, which are likely attributed to high aspect ratio of spindly shaped nano-CaCO3. In addition, the mechanical properties of PVC/nano-CaCO3 composites can be improved considerably when the content of nano-CaCO3 is 5–15 phr. Ultrasonic irradiation realizes the excellent dispersion of nanoparticles in the PVC, and offers a new way to deal with the challenges encountered in preparing polymer/nanocomposites materials.
A Feasibility Study on Micro Silicon Cantilever Beam for High Isolation RF MEMS Switch
Authors: Lin Lingling , Chen Feiyan , Hu Guoqing , Liu Wenyan , Wu Baihai
Published: June 2009

This paper presents a novel electrostatically actuated microelectromechanical switch. The structure of cantilever beam with electrodes sandwiched between Si and SiO2 layers has been established. Placing the pull-down electrodes outside the switching contact, the actuation voltage can be reduced while keeping high contact force and restoration force. The top and bottom dielectric materials separated two conducting electrodes when actuated. Thus, the reliability and the performance of the switch have been greatly improved. The charts of the deflection of the cantilever beam with respect to the voltage have been simulated with the MATLAB computer programming language.
Prediction of Temperature and Stress Distribution During Micro-Cutting of Ti-6Al-4V
Authors: Lu Dong , Li Jianfeng , Rong Yiming , Sun Jie , Wang Zhongqiu
Published: June 2009

A finite element method (FEM) for predicting the temperature and stress distribution in micro-cutting of Ti-6Al-4V is presented. The flow stress of Ti-6Al-4V is taken as a function of strain, strain rate and temperature in order to reflect realistic behavior in machining process. Diamond cutting tool is used. From simulation, cutting force, thrust force, cutting temperature and distribution of cutting temperature and stress are obtained. The effects of cutting speed and uncut chip thickness on the maximum temperature and maximum shear stress are analyzed and size effect is observed. The simulation results show that in micro-cutting of Ti-6Al-4V the maximum temperature locates on the shear plane. And the maximum shear stress locates on the stick region. The maximum temperature decreases as the uncut chip thickness decreases, and it increases with an increase in cutting speed. The maximum shear stress increases as the uncut chip thickness decreases, and it decreases with an increase in cutting speed.
A Method of the Comprehensive Evaluation of Surface Integrity in Micro- and Nano-Machining
Authors: Wang Guicheng , Zhang Chunyan , Pei Hongjie , Zhu Yunming , Shen Chungen , Wu Weiguo
Published: June 2009

The surface quality is always the crucial element of machined quality in precision ultra-precision metal cutting. A new concept that the surface integrity should include the edge quality of parts is put forward In this paper, the weight value of a series of characteristic parameters of surface integrity are calculated with using analytic hierarchy process, three basic methods of evaluating surface integrity are presented, and the comprehensive evaluation system has been formed which will theoretically play a great important role on rapid development in the precision machining.
The Uniaxial Tension Properties of Silver Nanorod by Molecular Dynamics Simulations
Authors: Chen Li , Liu Heng , Yu Lie
Published: June 2009

Using Sutton-Chen many-body potential, the mechanical characteristics of silver nanorod subjected to 001 uniaxial tensile strain are simulated with molecular dynamics. The results indicate that the tensile deformation process consists of an elastic and a plastic periods. The atomic configurations change little in elastic period but change obviously in plastic period. The changes of atomic configurations directly determine the corresponding stress-strain relation. The stress increases linearly as strain grows within the process of elastic deformation. The stress fluctuates greatly in plastic period. With detailed analysis, the dislocations and slips of atoms lead to the stress oscillation. The influences of size effects on tension properties are investigated simultaneously. Young’s modulus heightens and the elastic ultimate stress decreases with the increasing global size of nanorod. Both of them approach to that of macroscopic material as the global size increases. At the same time, the tension properties of Silver nanorod with vacancy defects are investigated. When the vacancy density is less than 0.1%, the Young’s modulus of defect crystals are almost same as that of free-defect crystals, but the elastic ultimate stress is less than that of free-defect crystals. The Young’s modulus and elastic ultimate stress and strain are all decrease with the increment of vacancy density.
A Study on Burr Formation and Controlling Technology in Precision or Ultra-Precision Drilling
Authors: Zhu Yunming , Wang Guicheng , Zhang Pingkuan , Ma Lijie , Zhang Chunyan
Published: June 2009

Burr formation is a common phenomena in metal cutting. The burr not only effect precision of parts directly but influence the assembly quality badly. Therefore, the control and deburring technology of machining burrs has become one of the key problem in precision or ultra-precision and automatic procession. In traditional drilling, the exit burr is bigger than the entrance burr, and its hazard is more larger. Moreover deburring process is very complex. According to these status quo, a new method of active control of the exit burr is put forward using vibration drilling. Mechanism of chip broken and burr formation in vibration drilling are analysed systematically and an equipment of vibration drilling is developed based on drilling experiment. Cutting test on A3 material, brass (H62) and 1Cr18Ni9Ti stainless steel is carried out using the method of vibration drilling. As a result, cutting character is improved because of the using of this method. Also, machining accuracy and surface integrality of parts are improved remarkably and the size of the exit burr is controlled effectively in vibration drilling. The development of vibration drilling device provides a new approach for the progress of ultra-precision drilling technology. Vibration drilling device and technology developed in this study can be widely used to ultra-precision machining.
Investigation of Electrospinning With Multi-Spinneret Array
Authors: Zhu Yongyang , Wang Xuexian , Wu Dezhi , Sun Daoheng
Published: June 2009

The influences of different applied voltages on spinnerets and distance between spinnerets are investigated when the spinnerets are arrayed in matrix shape in electrospinning. The models of one, two, three and nine spinnerets were set up and the electric field intensity was simulated and analyzed. By experiments, the voltage thresholds of ejection at different distance, the nanofibers electrospun by different distances between the spinnerets and different voltages were explored. The experiment results show that, in some extent of distance, the electric field intensity will decrease gradually with the distance between spinnerets rising. If the tips of multi-spinneret array are in the same distance to the collector, the voltage threshold of the center spinneret is extremely high and the solution is difficult to be ejected. If the same voltage is applied on multi-spinneret array, the quality of spinning becomes worse with the applied voltage increasing, that is, the nanofibers become more chaos and their diameters increase.
Polymer-Based Resonator for Ultrasonic Imagine Applications
Authors: Chang Ming-Wei , Deng Tse-Ming , Chiu Te-I , Chen Mu-Yue
Published: June 2009

Capacitive micromachined resonator for ultrasonic imaging technology is a prime candidate for next generation ultrasonic imaging transducers. Medical and healthcare imaging and the physiotherapy societies have expressed growing interest in capacitive micromachined resonator over the years. This paper focuses on polymer based fabrication technologies for capacitive ultrasonic resonator using in imaging applications. In this paper, the design, simulation, and fabrication results of a polymer based resonator for airborne ultrasonic application are presented. Due to its outperformance in terms of processing temperature and cost, this paper will also introduces the new concept in detail about sacrificial layer release processes during the fabrication of a polymer vibratile membrane. Process variations are compared qualitatively and quantitatively whenever possible. Through these study, it was concluded that polymer resonator technology was superior in terms of process control, yield, and uniformity. Because the number of steps and consequent process time were reduced, turn-around time was improved significantly. Furthermore, a resonator array was then designed and fabricated with a target DC actuation voltage of less than 20V with a resonance frequency at 1.7 MHz. The experimental results showed the potential of this resonator for healthcare imaging and the airborne applications in physiotherapy.
A Hybrid Parallelizable Algorithm for Computer Simulation of Rigid Body Molecular Dynamics
Authors: Duan Shanzhong
Published: June 2009

Molecular dynamics is effective for a nano-scale phenomenon analysis. This paper presents a hybrid parallelizable algorithm for the computer simulation of the motion behavior of molecular chain and open-tree structure on parallel computing system. The algorithm is developed from an approach of rigid body dynamics, in which interbody constraints are exposed so that a system of largely independent multibody subchains is formed. The increased parallelism is obtainable through bringing interbody constraints to evidence and the explicit determination of the associated constraint forces combined with a sequential O(n) procedure. Each subchain then is assigned to a processor for parallel computing. The algorithm offers a sequential O(n) performance if there is only one processor available. The algorithm has O(log2n) computational efficiency if there are as many processors available as number for molecular bodies. For most common scenario, the algorithm will give a computational complexity between O(n) and O(log2n) if number of available processor is less than number of molecular bodies.
A Micromachined Integrated Sensor for Pressure, Temperature and Humidity
Authors: Zhao Yulong , Jiang Zhuangde , Zhao Libo , Xu Jingbo
Published: June 2009

In this paper, the technology of a micromachined sensors chip, on which an absolute pressure sensor, a temperature sensor and a humidity sensor are integrated, is described. The absolute pressure sensor uses a bulk micromachined diaphragm structure with piezoresistors. For temperature sensing, a silicon temperature sensor is fabricated based on the spreading resistance principle. And the humidity sensor is a capacitive humidity one with polyimide film and interdigitated capacitance electrodes. The anisotropy of (100) n-type silicon is used to design and fabricate the integrated sensor chip. The different piezoresistive orientations are used for the absolute pressure sensor and the temperature sensor to reduce the interference between each other. The humidity sensor is made up of 49 pairs of aluminum electrodes and one kind of polyimide. This polyimide material consists of 65% polyvinyl alcohol and 35% carbon black. The fabrication and package processes are introduced. And the sensor chip size is 5mm × 5mm. Each sensor in the integrated chip shows good sensor characteristics except for humidity sensor. However, the linearity and hysteresis of humidity sensor can be improved by selecting the proper polymer materials and structure.
Design and Fabrication of a High Temperature Pressure Sensor
Authors: Zhao Libo , Zhao Yulong , Jiang Zhuangde
Published: June 2009

Based on Silicon on Insulator (SOI) and Micro Electro Mechanical System (MEMS) technology, a single-crystal silicon piezoresistive strain gage was fabricated and constituted by silicon substrate, a thin SiO2 layer by Separation by Implantation of Oxygen (SIMOX), an optimized boron ion implantation doping layer photo lithographed to discrete piezoresistors, stress matching Si3N4 layer, and metallization scheme of Ti/Pt/Au as beam lead layer for connecting piezoresistors to be Wheatstone bridge configuration. A special buried SiO2 layer with the thickness of 367 nm was fabricated by the SIMOX technology, which replaced p-n junction to isolate the piezoresistors from the bulk silicon substrate, so this kind of single-crystal silicon strain gage can be used in many harsh fields under high temperature up to 350°C. By the single-crystal silicon strain gage packaged on the metallic circular flat diaphragm, and along with other thermal treatments and compensating methods, a high temperature pressure sensor has been developed with the pressure range of 0–120 MPa under high temperature above 200°C. The testing results show that the sensor has good static performances under 200°C and fine dynamic characteristics to meet the requirements of the modern industry, such as petroleum and chemistry, mobile industry, military industry, wind tunnels, materials processing.
Nonlinear Vibration of Electrostatically Actuated MEMS Resonators Under Parametric and External Excitations
Authors: Zhang Wen-Ming , Meng Guang , Chen Di
Published: June 2009

Electrostatically actuated resonant MEMS (Micro-electromechanical Systems) have gotten significant attention due to their geometric simplicity and broad applicability. In this paper, analyses and simulations for the dynamics of electrostatically actuated MEM structures under parametric and external excitations are presented. The presented model and methodology enable simulation of the dynamics of the electrostatic MEM structure undergoing small motions. The numerical results showing the effects of varying the applied voltages and the squeeze film damping on the resonant frequencies and nonlinear dynamic characteristics are given in detail. Resonant frequency and peak amplitude are examined for variation of the dynamical parameters involved. It is demonstrated that the system goes through a complex nonlinear oscillation as the system parameters change. This investigation provides an understanding of the nonlinear dynamic characteristics of electrostatically actuated resonant MEMS.
Feasibility Study of Deep Micro Slit Making by Micro EDM With Flat Electrode
Authors: Cui Jing , Li Yong , Xiong Ying , Tong Hao
Published: June 2009

A new micro EDM technique was developed by combining the scanning and self manufacturing of flat electrode with micro slip machining. Compared to the methods of reverse-EDM with block electrode and WEDG, the self-manufacturing method of flat electrode is adopted to avoid the requirement for precision positioning between the electrodes. To manufacture micro slit on metal part, micro-EDM using flat electrode is suggested, which may have less electrode wear and higher efficiency than using rod electrode. With this method a raw rod electrode with negative polarity is used to scan a metal plate to form a through slit. Then the rod electrode is moved perpendicularly to the slit, off set from the center of the slit with certain distance. Micro flat electrode is obtained after the raw rod electrode is fed into the plate in the axial direction of the rod. Micro slits are achieved by scan machining with the micro flat electrode finally. At last deep micro-slits with aspect ratio of 18:1 and of parallel and equal width have been successfully achieved.
Co-Rich Amorphous Wire Study for GMI Micro Geomagnetic Sensors
Authors: Zhao Lin , Xia Linlin , Nie Qi
Published: June 2009

In this paper, a kind of micro geomagnetic sensor is researched due to the giant magneto-impedance (GMI) effect of Co-rich amorphous wires. It is proposed a multivibrator bridge should be adopted as the structure module, which can realize the circuit’s auto excitation. In sequence, the measuring principle of the sensor is intensively analyzed by establishing the mathematic model, which illustrates this sensor is a linear one. In addition, a signal processing system that includes differential circuit, low pass filter, amplifier circuit, CPUSCM, A/D conversion circuit and LED are introduced. The scheme shows that the sensitivity of this sensor can reach lager than 28mv /Oe by choosing appropriate parameters of the modules, and the calculated field error closes to 1.8%. This sensor is proved to be feasible for measuring weak signal of geomagnetic field, and it can greatly benefit further development of the geomagnetism-aided navigation.
A Low Temperature, Non-Aggressive Wafer Level Hermetic Package With UV Cured SU8 Bond
Authors: Wu Yexian , Tang Guanrong , Chen Jing
Published: June 2009

In this paper, we present a new technique that could realize wafer level 3-D hermetic package in a very low bonding temperature (120°C) for MEMS (Micro-electro-mechanical Systems) devices. Microcavities were etched on a host glass wafer and were bonded with a carrier silicon wafer. MicroChem SU-8 photoresist is used as the intermediate adhesive layer between the host and carrier wafer. The devices were fabricated by self-aligning etching technique and were finally sealed by coating the structures with sputtered aluminum. Helium leak testing is carried out to verify the hermetic characteristics of the package, 99.7% of the tested devices were qualified. This technology shows a significant improvement of the hermeticity properties of adhesive bonded cavities, making it particularly suitable for applications on gas-tightness with low temperature, non-aggressive demands.
Effects of Roughness of Solid Surface With Nano-Relief on Liquid-Wall Contact Angle
Authors: Qu Wei , Li Yuhua , Zhou Yan , Ma Tongze
Published: June 2009

The liquid-wall contact angle reflects the liquid wettability, the front size of thin liquid film, it is important for micro space phase change heat transfer. The smooth solid wall is supposed to have a periodic nano-relief, which has a roughness height and a roughness angle microscopically. The analytical contact angles are derived by the adsorptive potential and the disjoining pressure of adsorbed thin liquid film, depends on the scales of nano-relief and outside applying conditions. The results show that the adsorptive potential and the disjoining pressure of adsorbed thin liquid film will be affected by the nano-relief significantly when the roughness height is closer to the thickness of adsorbed thin liquid film. For apolar working fluids, if the roughness is medium, the analytical liquid contact angles are of the order of 0.010∼0.10 degree; if the roughness is extremely, then nano-relief of surface will exert stronger influences on the contact angles, the contact angle is nearly 90 degrees.
A New Friction Estimation Approach for Precision Positioner
Authors: Wang Wen , Li Xinxin , Chen Zichen
Published: June 2009

Precision positioner has been significantly developed as the rapid growth of MEMS and IC industries. As for short-stroke position, the loss of friction can be avoided by using flexible hinges. Long-stroke postioner, however, in which moved-to-be mass always stands on the guide-way part, a main source of friction, makes friction unavoidable. Friction estimation is based on certain filters, such as Extended Kalman filter (EKF). However, estimation accuracy of Kalman filter, especially at low-velocity movement, is not very well. To solve this problem, the paper proposes an estimation method based on DD2 to make an accurate estimation. And the result shows this method is promising in real-time friction estimation. After background introduction, in section 2, the relation of EKF and Taylor series and EKF implementation are reviewed and its limitations are noted as well. A briefly introduction to DD2 is given in Section 3 and friction estimation case comparing the simulation results of DD2 estimation with that of EKF described in Section 4, respectively. At last, conclusions are summarized.
The Electronic Structure of Truncated-Conical Shaped InAs/GaAs Quantum Dot With Wetting Layers
Authors: Liu Yumin , Yu Zhongyuan , Ren Xiaomin
Published: June 2009

Semiconductor quantum dots have been of major interest in recent years. This has largely been simulated by progress in quantum dot growth technology, whereby self-organized quantum dots array can be achieved using Stranski-Krastanow growth mode. Quantum does material has achieved broad applications in optoelectronic devices and quantum information fields because of the unique 3-D electron confinement. Based on the 1-band effective-mass theory, a finite element technique is developed to calculate the electronic structure of conical shaped InAs/GaAs quantum dot, including the wetting layer. Using the axis-symmetry model, the 3-D effective-mass Schro¨dinger equation with step potential barrier can be reduced to a 2-D problem by separating variable, which greatly reduced the calculation cost. Based on the result, we found, compared without wetting layer, the wetting layer can influence the electron level. This may attribute to the increase of the confining potential width rather than the potential height. The presented finite element code can be further used to analysis the transverse or vertical coupled quantum dot molecule.
Development of Micro Dieless Incremental Forming System
Authors: Lee Hye-Jin , Lee Hyoung-Wook , Lee Nak-Kyu , Lee Geun-An , Choi Soegou , Bae Sung-Min
Published: June 2009

The MEMS (Micro Electro Mechanical Systems) process is used in a micro/nano pattern manufacturing method. This method is based on the lithography technology. But the MEMS process has some problems such as complicated process, long processing time and high production costs. Many researchers are doing research in substitute manufacturing method to work out a solution to these problems. In this paper, we apply a dieless incremental forming technology to a substitute method of MEMS process. This dieless forming technology is using in the commercial scale sheet forming such as a prototype of automobile sheet parts. 5-axes CNC (Computerized Numeric Control) method are applied in this system to get a micro-scale dieless forming results. These 5-axes system are composed of precision AC servo motor stages (4-axes) and PZT actuator (1-axis). A PZT actuator is used in a precision actuating axis because it can be operated in the nano scale stroke resolution. This micro dieless incremental forming system has the advantage of minimization in manipulating distance and working space. As equipment and tools become smaller in size, minute inertia force and high natural frequency can be obtained. Therefore, high precision forming performance can be obtained. This allows the factory to quickly provide the customer with goods because the manufacturing system and process are reduced. To construct this micro manufacturing system, many technologies are necessary such as high stiffness frame, high precision actuating part, structural analysis, high precision tools and system control. To achieve the optimal forming quality, the micro dieless forming system is designed and made with high stiffness characteristic.
Automatic Flexible Wire Bonder for MEMS Sensor Packaging Based on Zoom Lens System
Authors: Chen Liguo , Sun Lining , Ma Lingyu
Published: June 2009

Generally, wire bonder for Micro-electromechanical Systems (MEMS) packaging uses conventional IC packaging technique for reference, but because of various different sizes and patterns of MEMS specially trained technicians must be needed to adjust the parameters of wire bonder. To reduce the product cost and simultaneously obtain high product quality, a flexible wire bonder system for automated wire bonding of MEMS sensors is developed. A manual wire bonder is reconstructed and integrated with visual feedback system. High magnification optical microscope is usually used to get highly accurate position of MEMS sensors. However, the small field-of-view of optical microscope essentially limits workspace of the micromanipulator and the low depth-of-field makes it difficult to handle micro parts. A zoom microscope is chosen to gain multiple magnification images for coarse-to-fine micropositioning. With low magnification, objects can be identified and located coarsely. The precise position of objects can be calculated accurately with high magnification images. The auto-focusing process and image segmentation method based on focus measures are described. At last, the productivity of the flexible wire bonder is validated through a wire bonding experiment for MEMS pressure sensors.
Joining Property of EPDM Rubber/Cast Iron Adherend by Functional Polymeric Nanofilm
Authors: Kang Zhixin , Zhong Chengwu , Wang Fen , Li Yuanyuan , Hirahara Hidetoshi , Mori Kunio
Published: June 2009

Joining of rubbers to metals are mainly divided into indirect joining and direct joining. Indirect joining with adhesives is unsuitable for complicated shape components and many adhesives are bad for the environment, whereas direct joining without any adhesive can overcome those problems. Polymer plating of 6-diallylamino-1,3,5-triazine-2,4-dithiol monosodium salt was employed for the fabrication of nanoscale film on the surface of high ductile spheroidal-graphite cast iron. With the prepared nanofilm having the affinity to EPDM rubber, direct joining of EPDM rubber/cast iron with good peel property and service performance was obtained in the process of crosslinking. The effect of crosslinking temperature on property of EPDM rubber/cast iron adherend was analyzed. It was found that the optimal crosslinking temperature is 418 K and crosslinking time is 7 min. Direct joining of rubbers/metals is suitable for adhering of complicated shape metallic parts/rubbers and for micro-joining of engineering assemblies.
Analysis of Micro Fluid Car Suspension System (MFCSS) and Effect of This on Comfort Factor and Life of System
Authors: Singh Neeraj Kumar
Published: June 2009

Suspension system is one of the most important factors for the comfort property in an automobile system. In general a simple suspension system in comprised of a spring and damper. Now a days there is lots of research going on to increase the comfort factor and the life of the suspension system. In this paper we analyse that some smart fluid like magnetorheological and electroheological materials belonging to a family of controllable fluids can increase the comfort factor and life of the car suspension system. These fluids can be defined as fluids in which the flow can be controlled through the application of an electric or magnetic field. The properties of these micro fluids, such as viscosity, elasticity and plasticity, change in the order of milliseconds in response. The Micro fluid car suspension system (MFCSS) can be capable of providing a wide dynamic range of force control for very modest input power levels. The fluid valve and associated design are fully contained within the damper.