bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical Evaluation on the Thermal Effects of Extracellular Hyperthermia and Intracellular Hyperthermia
Authors: Deng Zhong-Shan , Liu Jing
Published: June 2009

Although not currently a routine cancer treatment therapy, hyperthermia is developing rather rapidly as an alternative way as part of conventional treatment for some cancers. This treatment takes advantage of the high sensitivity of tumor cell to heat. Up to now, a variety of heating methods have been established to induce temperature rises either locally in target tissue region, or over the whole body. Among them, magnetic nano-particles offer some attractive possibilities in tumor hyperthermia, which have controllable sizes ranging from a few nanometers up to tens of nanometers. The magnetic nano-particles can be made to resonantly respond to a time-varying electromagnetic (EM) field, with advantageous results related to the transfer of energy from the exciting field to the nano-particles. This heat then efficiently conducts into the surrounding diseased cells and tissues. A major concern involved in magnetic nano-hyperthermia is about the controversy that whether intracellular hyperthermia is superior to extracellular hyperthermia [1]. The potential of time-varying EM heating effects in a scale length smaller than the biological cell diameter was first addressed by Gordon et al. and termed as “intracellular hyperthermia” [2]. Since experimental validation of the thermal effects of intracellular hyperthermia is still not feasible with the current experimental technique, this problem has been studied theoretically. However, different researchers have suggested different results, and the controversy still goes on [1–3]. In order to understand the exact micro-mechanisms of EM heating involved in intracellular hyperthermia and extracellular hyperthermia, an energy analysis is presented in this study to simulate the corresponding heat transfer problems thus involved. Different from intracellular hyperthermia, the main characteristic of the extracellular hyperthermia is to heat up the target tissue by EM energy absorption only in the extracellular medium. A series of numerical calculations for both intracellular hyperthermia and extracellular hyperthermia are performed. The results will answer the question from the heat transfer mechanism whether intracellular hyperthermia is superior to extracellular hyperthermia in the thermal sense.
Thin Liquid Film Profile Near the Interline Region in a Capillary Tube
Authors: Qu Wei , Feng Jianchao , Ma Tongze
Published: June 2009

Thin liquid film profile is important for heat transfer in microscale space. The asymptotic analytical solutions for thin liquid film profile in a capillary tube are obtained by the perturbation method. The variation of the film thickness, the contact angle of the vapor-liquid interface and its axial curvature depend on the effects of the disjoinng pressure and the capillary pressure. The thin liquid film profile will change significantly near the interline region. The obtained solutions are convenient and applicable for problems of thin liquid film in a capillary tube.
Analysis and Simulation of Micro Electro Discharge Machining Process
Authors: Gao Dedong , Tian Ling
Published: June 2009

Based on the basic thermal conductivity theory and the fact of micro electro discharge machining (micro-EDM), a finite element analysis model of micro-EDM is proposed. Through finite element analysis software ANSYS, the temperature field distribution of the single pulse discharge is simulated under the different heat source condition. It can be seen from the results that the shape of discharge crater is similar to that of molten zone of the temperature distribution. The surface roughness and material removed rate of single pulse discharge are calculated and analyzed by the numeric simulation results.
The Mechanism and Bonding Process of Field-Assisted Bonding of Borosilicate Glass to Kovar Alloy
Authors: Hu Lifang , Meng Qingsen , Liu Cuirong , Lu Xiaoying
Published: June 2009

The paper mainly investigates the field-assisted bonding process of Kovar alloy to Pyrex glass, the bonding is achieved at 350–450°C applying a voltage of 500–800v, and SEM EDS are used to analyze the bonding interface structure and the elements distribution. The experimental results indicate that there is a clear transitional area between the interface of the glass and the alloy. Owing to the formation of the transition area, the glass and the alloy are bonded together. The zigzag morphology in the interface of glass/alloy also indicates the diffusion of the elements. In the bonding process, the Na+ depletion zone, which gives birth to a electrostatic force is yielded in the glass. Due to the electrostatic force, the glass contacts with the Kovar alloy intimately. A model is built to analyze the dominant factor of the electrostatic force. Temperature, roughness of the sample and voltage are also the basic factors that influence the field-assisted bonding. The effects of these factors on the bonding process are analyzed in this paper. The experimental results suggest that the bonding area enlarges dramatically, if the voltage is increased. The bonding area enlarged from the initial contacting point and expands quickly. The influence of the time is small according to our experiments.
Testing the MEMS Device’s Internal Structure Topography Based on Transmission and Interference Technique
Authors: Xue Chenyang , Kong Fanhua , Zheng Lina , Zhang Wendong , Xiong Jijun , Zhang Binzhen
Published: June 2009

Based on the principle of white light interference with the Micro System Analyzer ( MSA400 ), the sample of the comb bonded silicon with glass from the Peking University is investigated. In the experiment, the light can transmit through the glass and interfere. Through analyzing the changes of the interference stripes and using the method of envelope to deal with the result, the internal structure of the MEMS can be shown and its geometry dimension and 3D topography can be measured with the testing exposure time 1/250s and 1/300s respectively. From the analyses, the depth of the groove constituted by the combs of the resonator is 84.43um, the width 10um and the depth-to-width ratio 8:1.
An Experimental Study of TMAH Etching Silicon for MEMS
Authors: Chen Feiyan , Hu Guoqing , Wu Baihai
Published: June 2009

In the process of Micro-Electrical-Mechanical System (MEMS), the anisotropic wet chemical etching rate of the silicon wafer is very important for fabricating MEMS to determine the fabricating method, processing and etching time. The etching rates of the silicon wafer in the TMAH solution with the different temperature are obtained in this paper. The micro-fabrication technology and micro-fabrication process are also discussed. In the same time, all experimental data are put forward in details.
Multiobjective Topology Optimization of Compliant Microgripper With Geometrically Nonlinearity
Authors: Li Zhaokun , Zhang Xianmin
Published: June 2009

Since compliant mechanism is usually required to perform in more than one environment, the ability to consider multiple objectives has to be included within the framework of topology optimization. And the topology optimization of micro-compliant mechanisms is actually a geometrically nonlinear problem. This paper deals with multiobjective topology optimization of micro-compliant mechanisms undergoing large deformation. The objective function is defined by the minimum compliance and maximum geometric advantage to design a mechanism which meets both stiffness and flexibility requirements. The weighted sum of conflicting objectives resulting from the norm method is used to generate the optimal compromise solutions, and the decision function is set to select the preferred solution. Geometrically nonlinear structural response is calculated using a Total-Lagrange finite element formulation and the equilibrium is found using an incremental scheme combined with Newton-Raphson iterations. The solid isotropic material with penalization approach is used in design of compliant mechanisms. The sensitivities of the objective functions are found with the adjoint method and the optimization problem is solved using the Method of Moving Asymptotes. These methods are further investigated and realized with the numerical example of compliant microgripper, which is simulated to show the availability of this approach proposed in this paper.
Synthesis and Properties of Cobalt Nanowires
Authors: Liang Jianyu , Xia Zhenhai
Published: June 2009

Understanding the structure and properties of metal nanowires is critical for the atomic-scale manipulation, design and application of those materials. Currently, active research on structure and behavior of various metallic nanowires has been carried out by computer simulation. Much experimental work has been done for synthesizing various metal nanowires by many different methods. To experimentally explore the mechanism of the behavior of and the development of structures in the nanowires, it is desirable to have the capability of synthesis various metal nanowires with controlled size, length, uniformity and aspect ratio. It is also desirable to further process those metal nanowires to engineer their properties. In our study, a template assisted fabrication method has been employed to fabricate various metal nanowire arrays, including cobalt, iron and nickel. This fabrication method offers us command over the size and length of the nanowires with excellent uniformity. Heat treatments were used to further process the metal nanowires. The structure of cobalt nanowire array has been investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mechanical properties of the metal nanowire array will be investigated through nanoindentation and atomic force microscopy (AFM).
Precision Motion Control of Linear Motor Drive Systems for Micro/Nano-Positioning
Authors: Yao Bin , Hong Yun , Hu Chuxiong , Wang Qingfeng
Published: June 2009

Micro and Nano-technologies need precision machines that can produce motion accuracy down to micro/nano-meter range. At the same time, these machines have to operate at high speeds to yield high productivity. Such an increasingly tight control performance requirement puts a significant challenge to control community and forces control engineers to look beyond traditional linear control theory for more advanced nonlinear controllers. This research is to present an advanced nonlinear adaptive robust control approach to achieve micro/nanometer level positioning accuracy for micro/nano-manipulation type applications. In addition, the proposed control strategy is implemented on a commercial linear motor drive system with a position measurement resolution of 20 nanometers by an external laser interferometer. Experimental results for both long-range high-speed/high-acceleration motions and short-range slow motions are presented to demonstrate the precision motion that can be achieved by the proposed method and various practical issues that remain to be solved. It is found that for motions with a maximum speed of 2 m/sec and maximum acceleration of 45 m/sec2, the steady state position tracking error is within the linear encoder resolution of 0.5 μm when the system comes to a stop and within 5 μm during the 2 m/sec constant speed period. Furthermore, the maximal position tracking during the entire motion is mostly within 20μm. For slow motions with a maximal speed of only 0.0002m/sec, the steady state position tracking error with the external laser interferometer position measurement is mostly within 0.1 μm when the system comes to a stop and within 0.2 μm during the constant low speed period, and the maximal position tracking during the entire motion is within 2μm.
The Research on the Redundant Actuated Parallel Robot With Full Compliant Mechanism
Authors: He Guangping , Lu Zhen
Published: June 2009

In the field of MEMS, optical instruments and communication, the manipulation tasks such as mechanics property test of micro-material, micro-components assembling, and fibers connecting, are challenging for their minuteness and accuracy. It is measured in the scale of micrometer or sub micrometer. The full-compliant mechanisms are the best alternative, which are characteristically of their compliant hinge, and monolithic chip forming, and can be used for transmit a certain high-accuracy motion. Nevertheless, the full-compliant mechanisms have some shortages, for instance, small working space, nonlinear in large range motion, complicated in kinematical and mechanics etc. inherited from the parallel mechanisms that instructs the design of full-compliant mechanism generally. In this article, the redundant actuated parallel robot with full compliant is introduced to overcome some shortcomings of the full-compliant mechanism. The redundant actuated mechanisms provide redundant inputs and can be used in some complicated force manipulations, for example, improving the stress distribution while implements the main task for enhancing the fatigue nature of the complaint mechanism itself. As an example, a 3-DOF planar redundant actuated full-complaint robot is studied both in the modeling and control system.
Sliding Mode Based Controller for Magnetostrictive Actuator in Precision Positioner
Authors: Li Xinxin , Wang Wen , Chen Zichen
Published: June 2009

Magnetostrictive actuator, for its merits of relatively low voltage and high force, has been increasingly applied in many applications, such as vibration control, aviation, positioner, etc. At low drive level, magnetostrictive actuator presents linear relation between strain or displacement and input voltage or input current, while non-linear appears when applied moderate or high drive level. To achieve accurate control for high drive level, non-linear, including saturation and hysteresis, must be compensated. Sliding mode control, a robust control scheme, can handle these non-linear. As magnetostrictive actuator modelled in Jiles-Atherton model, the relation of magnetic field H and bulk magnetization M, hysteresis, is divided into anhysteresis and deviation from anhysteresis. Saturation can be compensated by inversion of anhysteresis (free-hysteresis) and then, hysteresis, represented as the deviation from anhysteresis, is compensated with sliding mode control.
Manufacturing Heat Pipe by Combined Ploughing-Extrusion Process
Authors: Liu Xiaoqing , Tang Yong , Pan Minqiang , Jiang Lelun
Published: June 2009

Since the capillary structures in the internal wall of heat pipe dominate the heat transfer performance, the research of surface heat functional structure is being gradually extended to the fields of metastructure and microstructure. This paper proposes a combined ploughing-extrusion method with a multi-tooth tool to form the micro-groove structures in the internal surface of copper pipe. Experiments indicate that the combined ploughing-extrusion process can create rougher surface than the single ploughing-extrusion process, and some phoenix-feather-like structures appear. The capillary force comparative experiment indicates that the heat pipe manufactured by the combined method can absorb 0.2ml more liquid than the one made by single process, supposing there is 90ml liquid in the container. The heat transfer testing experiment also indicates this heat pipe can transfer more heat when the inclination angle is small, but with the increase of inclination angle, this superiority becomes not so evident due to the increased reflow resistance. The combined process that comprises more than two processes makes metal yield and generates cracks in the internal wall.
A Simulation and Study on Strain Uniformity of Equal Channel Angular Pressing
Authors: Xu Xiaojing , Cao Jinqi
Published: June 2009

The preparation of dense bulk nanostructured materials is becoming an important research subject with the development of nanostructured materials. Equal Channel Angular Pressing (ECAP) is thought to be one of the major technologies to prepare bulk nanostructured or ultra-fine grained metals, which can improve the mechanical property of materials considerably, but its processing effect was affected by many factors, such as press route, angle of channels, etc. Since some questions in the procedure of ECAP were not understood clearly, the researchers have different judgments on these factors affecting the result of ECAP processing. There were few reports about the processing condition that affect the strain uniformity, most of which deal with only 1 and 2 passes of ECAP. In present paper, a model dealing with four connective channels which can implement the continuous 4 passes ECAP processing was established firstly, the finite element software, DEFORM-3D, was used to simulate the processing of ECAP to study how the processing condition (press route and structure of die such as the channel angle and inner-arc radius) to affect the strain uniformity. Results show that the influence of press route is associated with pressing passes. In term of 4 passes pressing, route Bc has a most uniform distribution of strain, while in term of 2 passes pressing, route C can get a good strain uniformity. In addition, with the increase of channel angle and inner-arc radius, the strain uniformity was also improved considerably. So to get the best strain uniformity all the above factors should be taken into consideration.
Research on Mechanism of Ultra-Precision Electrical Discharge and Mechanical Grinding for Nonconductive Engineering Ceramics
Authors: Ji Renjie , Liu Yonghong , Yu Lili , Li Xiaopeng
Published: June 2009

A new method known as electrical discharge and grinding with synchronous servo double electrodes (EDGSSDE) is presented in this paper for nonconductive engineering ceramics which integrates electrical discharge and mechanical grinding with a metal bonded diamond conductive wheel. Also the mechanism of this method is analyzed. The results show that electrical discharge and electrolysis occur simultaneously during the process, which makes the diamond grains always in knife-edge, and achieves in-process dressing of grinding wheel. Due to the effects of high temperature and high heat generated by electrical discharge, a metamorphosed layer is formed on the surface of ceramics, which debases the rigidity of workpiece. The conductive grinding wheel grinds the metamorphosed layer and achieves paucity of ceramics removal by minute fritter. This method can dress grinding wheel in-process, avoid micro-crack that produced in traditional engineering grinding, reduce the grinding force, improve the service life of grinding wheel, advance the surface quality and machine nonconductive engineering ceramics in ultra-precision.
A Novel Demodulation Scheme in the Digital Readout System for a Micro-Machined Gyroscope
Authors: Liu Lu , Song Yi-Chao , Chen Xu-Zong
Published: June 2009

A novel demodulation scheme with Sage-Husa adaptive Kalman filtering algorithm is presented for the digital readout system of a micro-machined gyroscope. Based on the analysis of the detection signal from gyroscope, a mathematical model of the detection signal is established in the condition of the additive white Gaussian noise, and the state and observation model for the demodulation scheme are also given. Moreover, the simulation system is built by the Matlab/Simulink. Assuming the input signal of angular velocity is the step or sine function, and the statistical characteristics of the noise in the detection signal are unknown, simulations are given to demodulate the detection signal with different SNRs (signal-to-noise ratio). In addition, the phase sensitive demodulation scheme in the analog readout system is simulated for comparison. Results show that, the demodulation gains reach +24.23dB (input SNR is above −12.04dB) and +23.92dB (input SNR is above −16.99dB) respectively when the angular velocity input is Ω = 0.005[deg/s] for the step function, while Ω = 0.005 sin(2π × 50t)[deg/ s] for the sine function. Meanwhile, the demodulation gain increases along with the decreasing SNR of the detection signal. Compared with the analog phase sensitive demodulation scheme, the demodulation output with Sage-Husa adaptive Kalman algorithm has the shorter convergence time, but about 5dB higher of MSE (mean square error). In conclusion, the novel demodulation scheme with Sage-Husa adaptive Kalman filtering algorithm can real-timely and precisely estimate the covariance of dynamic noise in the detection signal from gyroscope, and increase the SNR of the demodulation signals dramatically. It can demodulate the angular velocity accurately and quickly, and shows a good practicability.
Study on Novel MEMS Hollow Microneedle Array
Authors: Jia Shuhai , Li Yigui , Sun Xiao , Zhu Jun
Published: June 2009

A novel MEMS hollow microneedle array is fabricated through the exposure technique in deep X-ray lithography and development procedure in this paper. The method to fabricate microneedle array presented in this paper needn’t any special apparatuses, and is very easy to operate. A method to compensate the beam distribution of synchrotron radiation light source is described. The PMMA (polymethylmethacrylate) sheet is chosen as the material of microneedle. The length of the hollow microneedle fabricated is 160μ m. The outer diameter of microneedle is 80μm, and the inner diameter of microneedle is 40μm. The mechanical characters of microneedle, such as the force withstanding capabilities, are studied through both the theoretical analysis and numerical simulation of finite element method. The analysis results of the mechanical character show that the strength of microneedles fabricated in this paper is enough to pierce human skin.
Femtosecond Laser Pulse Train Effects on Optical Characteristics and Nonequilibrium Energy Transport in Metal Thin Films Considering Quantum Effects
Authors: Sim Hyung Sub , Lee Seong Hyuk , Park Seungho , Choi Young Ki , Lee Joon Sik
Published: June 2009

The objective of this study is to investigate numerically the electron-phonon interactions and the nonequilibrium energy transfer in metal thin films irradiated by ultrashort pulse train lasers. During laser irradiation, in particular, the temporal and spatial variations of optical properties are discussed and the influence of pulse number per train and pulse separation time is also examined. The present study uses the well-established two temperature model in describing laser-solid matter interactions and it also adopts the quantum approach to determine various properties such as electron heat capacity, electron thermal conductivity, collision frequencies, reflectivity, and absorption rates. It is found that as the pulse number per train increases, the nonequilibrium state between electrons and phonons disappears gradually because of the energy relaxation and the low electron thermal conductivity. From the results, the electron-electron and electron-phonon collision frequencies are changed significantly with the pulse number per train and the separation time per pulse, and they affect considerably reflectivity and absorption rate, leading to the change of ablation mechanism of thin metal films for the pulse train laser heating.
Research of Nanometer Positioning Stage With Six Degree of Freedom Based on Binary Actuation Principle
Authors: Sun Shufeng
Published: June 2009

To adapt the miniaturized development tendency of nanometer positioning devices, a new type of micro-displacement stage with six degree of freedom, which can implement nanometer-level ultra-precision positioning without feedback control is designed. It takes a group of piezoelectric ceramics actuators (PZTAs) connected in series as actuation unit, takes flexure hinges as elastic guide rail. To overcome the non-linearity and hysteresis of PZTAs, binary actuation principle is adopted to control a group of actuators that work together to output many discrete, repeatable displacements. If these displacements are distributed within a scope of several microns, only simple on and off actuator commands may obtain nanometer-level repeatable positioning without feedback control. Theoretical calculation and finite element analysis (FEA) are used to design and simulate the stage. Expressions of rigidity and stress are obtained by theoretical calculation. FEA and experimental results verify the rationality and feasibility of the stage.
Molecular Dynamical Study on the Nanoscale Effect of Particles on the Thermal Conductivity and Viscosity in Nanofluids
Authors: Lu Wen-Qiang , Fan Qing-Mei
Published: June 2009

Molecular dynamics (MD) simulation method is used to simulate the thermophysical properties of nanofluids: thermal conductivity and viscosity. This paper reports a better agreement between present numerical results and experimental data. It shows MD to be an effective method to forecast some thermal properties of nanofluids. Many former experiments have shown that this new heat transfer fluids - nanofluids can greatly enhance the heat-transfer efficiency. This work further gives the effects of the volume fraction and the size of nanoparticles on the thermal conductivity and the viscosity of nanofluids. Numerical results show that, decreasing size of nanoparticle or increasing the volume fraction can increase thermal conductivity with increasing viscosity; for suitable volume fraction and size, increasing viscosity with improving heat transfer capability is acceptable.
Variation of Macroscopic Shape and Microstructure of Silver Nanoparticle Suspension Droplets Using Ink-Jet Printing
Authors: Tsai Ming Hsiu , Hwang Weng-Sing , Chen Hao-Long
Published: June 2009

Micro-interconnects of integrated circuit (IC) devices were produced using ink-jet printing of Ag nanoparticle suspensions. The macroscopic shape and microstructure of the Ag micro-dot deposits using ink-jet printing were observed using SEM (Scanning Electron Microscope) and EDS (Energy-Disperse Spectrometers). The well-dispersed suspension of nanoparticle Ag colloids, which was made up of 5–10 nm silver particulates, allows low-temperature sintering of Ag. The 50 wt% Ag suspension had a viscosity of about 7.95 cP at 25°C, which is appropriate for printing jobs. A bipolar voltage signal was used to drive a piezo-electric droplet generator and then 50–70 μm diameter droplets was dispensed on the substrate. Using SEM, a smooth deposition of drying silver dot morphology was observed. Drying the silver dots was improved by using hydrophobic substrates and a slow evaporation rate of suspensions was used to resolve an unexpected ring-shape, because both are able to control the interactions among the self-assembled Ag particles, surface tension, and the evaporation rate of droplets. Finally, the deposit/substrate composite was processed at 300°C for 60 min under a pure oxygen atmosphere to allow for the complete evaporation of the carrier and for sintering of the nano-particles, thereby yielding a finished circuit interconnect.
Study on Control Method of AFM Probe Based Nanomanipulation
Authors: Hao Lina , Zhang Jiangbo , Xi Ning
Published: June 2009

Atomic Force Microscope (AFM) based nanomanipulation has been extensively investigated for many years. However, efficiency and accuracy of AFM based nanomanipulation is still a major issue due to the nonlinearities and uncertainties in nanomanipulation. The compensation of drift, creep, hysteresis and some other nonlinearities generating large spatial uncertainties has been studied by some research groups. The compensation of these uncertainties does help to improve the accuracy of nanomanipulation to a certain extent. However, the deformation of the cantilever is one of the major nonlinearities affecting the accuracy during manipulations. It is difficult to control the tip position precisely due to the uncertainty of the deformation. A promising way to solve this problem is to actively change the nominal rigidity of the cantilever. This paper focused on the accurate control of active AFM probe based on survey of existing way to eliminate the deformation. The experimental results have verified the theoretical model and demonstrated that the precise position control.
Study on the Micro Milling Process of the Inertial MEMS Components
Authors: Wang Bo , Zhao Yan , Liang Ying Chun
Published: June 2009

Micro milling technology is used in the manufacturing of the inertial MEMS components with 3D micro structures. Firstly, a 3-axis micro milling machine was developed. The positioning accuracy of all the 3 axis is better than 0.25 μm and the highest spindle speed is 160,000RPM. Then, using this machine, the optimal cutting parameters are studied and the components are successfully manufactured. Finally, to ensure the stable performance of the components, laser cofocus microscope and a new method called micro-bridge method is introduced to estimate the roughness, elastic modulus and residual stress of the micro milled thin-walled structures in the inertial MEMS components and this is a good try to evaluate the surface quality produced by micro milled method.
Fuel Cell Stacks Based on Micro Fuel Cell Units for a Substantially Increased Power Density
Authors: Cao Yiding
Published: June 2009

This paper introduces a bio-inspired fuel cell stack that has a substantially increased specific reactive surface area. The fuel cell stack is based on micro fuel-cell units that generally has a circular shape and an effective diameter on the order of 1 mm. A number of fuel cell units are arranged to form a fuel cell module, and then these modules are stacked one over another and electrically connected to form a fuel cell stack. An evaluation on the stack indicates that the specific reactive surface area may be increased by more than 10 fold compared to a conventional bipolar plate based fuel cell stack. A fuel cell stack that has such a substantially increased specific reactive surface area may enable a substantially increased power density, a substantially reduced fuel cell stack size, and an improved energy utilization efficiency. Additionally, the present fuel cell stack eliminates the fuel sealing problem in a planar fuel cell stack and allows a much higher operating pressure difference between the fuel and air streams.
Effect of Al2O3 Microparticles on the Heat Transport Capability in an Oscillating Heat Pipe
Authors: Gao Hongtao , Gao Xiangyang , Ma Hongbin , Jiao Anjun
Published: June 2009

An experimental investigation was conducted to determine the microparticle effect on the heat transport capability of an oscillating heat pipe (OHP). The OHP was fabricated from copper tubing with inside diameter of 1.52 mm. The heat pipe consists of the evaporator, adiabatic section, and condenser. When heat load was added to the evaporator of OHP, the strong oscillating motion was generated. Due to the strong oscillation and circulation motions, the heat transport capability of OHP was significantly increased. The experimental results show that there exists an optimum volume ratio of microparticles added into the working fluid. The effects of filling ratio and tilted angle on the heat transport capacity were also conducted.
A High G Accelerometer Based on SOI Piezoresistive Material With Cantilever Beam
Authors: Zhao Yulong , Zhao Libo , Gao Jianzhong , Jiang Zhuangde
Published: June 2009

A high g accelerometer based on Silicon-On-Insulator (SOI) piezoresistive material with cantilever beam is described, which can measure the acceleration up to 105 g. The excellent electrical and mechanical properties of SOI material may be suitable in the applications of the high-g force accelerometer as an electromechanical sensor. One kind of SOI Wheatstone bridge strain silicon gauge is developed, and the size of the SOI silicon gauge is 1.8mm×1.6mm×0.2mm. A kind of cantilever beam structure is designed to endure the impact of high-g acceleration. The SOI silicon gauge is bonded on the cantilever beam by the way of AuSn eutectic. The fabricated devices have been subjected to shock tests up to 105 g by using a Hopkinson’s bar, the resonance frequency of which may be up to 40 kHz. The design modeling procedures and results are reported and the fabrication steps are described.
Structural Design and Porting Parameters Calculation of a Micro Piston Engine for Power Generation
Authors: Wang Jiuhong , Lu Dejiang , Jiang Zhuangde
Published: June 2009

In this paper, a new type micro piston internal combustion engine is reported. The micro engine can be used to provide mechanical energy for micro electric power generation system. It is consisted of three or four planar plate structure. This micro engine has special advantages in structure which are more suitable to minimize whole engine to MEMS dimensions than traditional engines. Compared with traditional or other existing micro piston engines, there is a sliding chute and crank mechanism rather than a crank and connecting rod mechanism to improve the space utilization ratio. The crank is fixed on the plate next to the main body plate of the engine. A free piston micro engine without the crank and connecting rod mechanism is given too. Scheme of structure, operation and characters of the micro engine are described in detail. The displacement, velocity and acceleration functions of piston are deduced to understand the rules of piston motion. Calculating formulas of porting parameters are deduced too. Finally, an example of the micro engine with specific design parameters is given. Mathematic modeling of the porting parameters is built. The calculation results show that the phase angles of the inlet, scavenging port and the exhaust port of the example engine are respectively of 21.78°, 156.27° and 158.39° under following conditions. Compression ratio is 5; working volume is 5mm3; length of stroke is 2mm; the sectional dimension of the piston is 2mm×1mm; and the value of revolution is 9000RPM. When the width of gas ports are all 1mm, the heights of inlet, scavenging port and exhaust port corresponding to the port phase angles above are respectively 72μm, 85μm, and 70μm. According to the assembly testing on computer, it is shown that the micro piston engine presented here is workable, controllable and suitable for MEMS fabrication in structure. It can be used as device to provide mechanical energy for micro electric power generation system.
Several Key Technologies to Improve Silicon Microgyro Performance
Authors: Xia Dunzhu , Zhou Bailing , Wang Shourong
Published: June 2009

Silicon micromechanical gyroscope is an extraordinarily important micro inertial sensor, which has characteristics of little size, low cost and batch integrated production with huge market. But it now belongs to low or middle level precision angular rate sensor, so it is becoming a key problem to update this sensitivity to high level. This paper presents several key technologies to improve silicon microgyro performance from the view of micro-electro-mechanical working principle and minor signal detection of microgyro. The simulation and circuit design are well done, which results testify that these improved technologies have certain academic and practical value to update present low or middle level precision angular rate sensor.
Preparation and Mechanism of Natural Brucite Nanofibers
Authors: Xu Li , Ni Wen , Yang Xiaoguang , Yang Hailong , Liu Wei , Li Shiqing , Zhao Juncai
Published: June 2009

Test results indicate that brucite fibers could be well dispersed by using OT as the dispersant at the water/solid ratio of 20:1, at the dosage of 15% of fiber quality and in the dispersing duration of 30 minutes. The prepared nanofibers were characterized with a scan electron microscope (SEM) and a transmission electron microscope (TEM). Test results indicate that the prepared single brucite nanofiber was around 30nm long in diameter and the talus of non-single brucite nanofibers was about 50nm∼150nm long in diameter. Brucite nanofibers may be used as a fortifier for compound such as the SiO2 aerogel super insulating materials. Since brucite is also an excellent fire retardant, brucite nanofibers are expected to be used widely in the high-molecular materials sector.
Hydrophobic Surfaces Prepared by Aluminum-Induced Crystallization of Amorphous Silicon
Authors: Song Ying , Premachandran Nair Rahul , Zou Min
Published: June 2009

This paper reports fabrication and understanding of hydrophobic silicon nano-textured surfaces produced by aluminum-induced crystallization (AIC) of amorphous silicon (a-Si). In this study, the effects of annealing temperature and duration on surface topography and wetting property were investigated. The results showed that surface wetting property directly correlates with the percentage area coverage by the nano-textures, which in turn was determined by the annealing conditions. The largest water contact angle (WCA) obtained from this research is 137°.
Ion Bombardment as Dominant Factor in Plasma Cryo-Etching for High Aspect Ratio Silicon Structures
Authors: Lu Dejiang , Jiang Zhuangde , Wang Jiuhong
Published: June 2009

SF6/O2 Plasma cryo-etching is discussed to show that it is a promising technology for etching the high aspect ratio silicon structures. Through a series of etching experiments, process factors including chuck temperature, gas composition, chamber pressure and ICP coil power are variated to show their influences to the etching results. Some valuable details of the experiment data point to some key mechanisms of the cryo-etching. It is not the surface chemical reaction but the ion bombardment that dominates the cyro-etching process in most cases. Notching near to the mask is due to the discharging effects of dielectric layer, and ARDE effect here is also different from the usual etching processes but is driven by the sidewall step coverage effect to the ion sputtering.
Joining Mechanism of Static Bonding Between β"-Al2O3 and L2-Aluminum
Authors: Liu Cuirong , Meng Qingsen , Hu Lifang
Published: June 2009

Electrostatic bonding, as a special method of solid-state diffusion bonding for the ceramics and the metals, can be performed at low temperature quickly and conveniently. And It’s suitable for making micro electromechanical system (MEMS), such as micro-devices, solar cell and micro-sensors. So Electrostatic bonding process mainly is used to bond the fast-ion conductivity materials and the metals. The bonding technique of functionally materials and metals had a significant role in the manufacture of MEMS. In this paper, the L2 aluminum film and β"-Al2O3 sheet were bonded by the electrostatic bonding process. SEM, EDX, XRD were applied to investigate the interfacial structure and composition of the samples, and the bonding mechanism and technical condition were characterized precisely. The experimental results showed that the electrolyte ceramics and aluminum can be bonded very well. The bonding area was composed of Al metal, transition area and aluminum oxide. The successful bonding was achieved due to the formation of the oxide in the interface. The main factors that influenced the bonding process were voltage, temperature and the electrical conductivity of the materials.
Micro Channel Structure With Strengthened Rough Surface in an Ethanol Reforming Hydrogen Generator
Authors: Su Dashi , Tang Yong , Pan Mingqiang
Published: June 2009

The combination of the hydrogen production from ethanol and microchannel technology can provide a portable hydrogen resource for fuel cell, which will effectively solve the energy and environment problem. This paper introduces a new surface structure — microchannel structure with strengthened rough surface (MCSWSRS) which has a feature of strongly transferring heat in microchannel. The MCSWSRS depends not only the dimension effect of this structure but also the special rough surface to strengthen heat transmission, so MCSWSRS transfers more heat than the smooth structure. Based on the heat strengthening transmission mechanism of MCSWSRS and the microchannel theory, a new kind of microchannel reactor was built and its heat strengthening transmission property has been analyzed. When the reacting temperature of microchannel reactor was 330°C and catalyst was Ni/La2O3, properties of MCSWSRS were experimented in the system of hydrogen from steam reforming of ethanol. The experimentation shows that hydrogen production efficiency of this microchannel reactor with MCSWSRS was 9% higher than that of the fixed bed tube reactor under the same reacting conditions. The results show that the MCSWSRS in reactor is feasible and advantageous in practice.
Study and Measurement of Micro-Scale Bonding Strength in Vertical Direction
Authors: Liu Dongning , Zhang Dacheng
Published: June 2009

A new way to evaluate the strength of micro-scale bonding is developed by using a silicon cantilever beam bonded on the substrate by a small anchor. The central concept is that the bonding area will be fractured when a certain vertical force is loaded on it, and this force can be used as a “standard”. This test is easy to be carried out. It also can be used in in-situ bonding quality monitoring in MEMS fabrication. Edge effect, the length of the bonding area partly determines the bonding strength, is found in micro-scale bonding. The coefficients of the edge effect, which determine the bonding strength at the interface of the bonding are, are calculated. Designers can use the equations and the coefficients to design the bonding areas according to the requirement of bonding strength for their devices or the appropriate test structures for the bonding quality in-situ monitoring.
Molecular Dynamics Simulation of Au Cluster Depositing on Au Surface in Cold Gas Spray
Authors: Gao Hong , Zhao Liangju , Zeng Danling , Gao Lijuan
Published: June 2009

Cold gas spray is a relatively new coating technique by which coatings can be formed without significant heating of the sprayed powder. In contrast to the conventional thermal spray processes, such as flame, arc, and plasma spraying, in cold spraying there is no melting of particles prior to impact on the substrate. In cold spray, particles are accelerated to a very high velocity by a flowing gas with supersonic speed and the temperature of spray particles is much lower than its melting point. However, being accomplished in so short an interval, the impact and deposition processes are difficult to be observed by experimental ways. Using molecular dynamics simulation, the deposition of nano-scale Au clusters on Au (001) surface was studied. The many-body potential is used to simulate the interatomic force between the atoms. By taking “snapshot”, the impact, deposition process and the final appearances of the cluster and the substrate were observed directly. It is found that both the substrate and the cluster deform and lose the crystalline structure. But after reconstruction and relaxation, both of them recover the crystalline structure. By calculating the temperatures of the substrate and the local area influenced by impinging, it is found that the melt phenomenon occurs during impact and deposition, whereas the temperature of the rest region of the substrate is still below the melt point. In addition, the influence factors on deposition, such as incident velocity and the size of the cluster, are discussed in the paper. Simulation results show that the higher incident velocity or the larger size of the cluster could result in stronger interaction between the substrate and the cluster owing to the higher kinetic energy of the cluster.
Polymer brushes and self-assembled monolayers: Versatile platforms to control cell adhesion to biomaterials (Review)
Authors: Raynor Jenny E. , Capadona Jeffrey R. , Collard David M. , Petrie Timothy A. , García Andrés J.
Published: June 2009

This review focuses on the surface modification of substrates with self-assembled monolayers (SAMs) and polymer brushes to tailor interactions with biological systems and to thereby enhance their performance in bioapplications. Surface modification of biomedical implants promotes improved biocompatibility and enhanced implant integration with the host. While SAMs of alkanethiols on gold substrates successfully prevent nonspecific protein adsorption in vitro and can further be modified to tether ligands to control in vitro cell adhesion, extracellular matrix assembly, and cellular differentiation, this model system suffers from lack of stability in vivo. To overcome this limitation, highly tuned polymer brushes have been used as more robust coatings on a greater variety of biologically relevant substrates, including titanium, the current orthopedic clinical standard. In order to improve implant-bone integration, the authors modified titanium implants with a robust SAM on which surface-initiated atom transfer radical polymerization was performed, yielding oligo(ethylene glycol) methacrylate brushes. These brushes afforded the ability to tether bioactive ligands, which effectively promoted bone cell differentiation in vitro and supported significantly better in vivo functional implant integration.
Toward protein imprinting with polymer brushes
Authors: Zdyrko Bogdan , Hoy Olha , Luzinov Igor
Published: June 2009

The authors described an original approach for a surface protein imprinting employing grafting of polymer brushes. Protein molecules were first chemically bound to an ultrathin (1–3 nm) poly(glycidyl methacrylate) reactive polymer layer and later removed by protease treatment. Residual amino acids became grafted to the surface and to a certain extent imitated the surface chemical composition and shape of the template molecule on a nanolevel. The space surrounding the adsorbed biomolecules was modified with grafted poly(ethylene glycol) layer. This led to the formation of islands of spatial nanosized pockets complementary to the protein shape. The adsorbing protein recognized the surfaces imprinted and was anchored to the substrate.
Stimuli-responsive command polymer surface for generation of protein gradients
Authors: Ionov Leonid , Houbenov Nikolay , Sidorenko Alexander , Stamm Manfred , Minko Sergiy
Published: June 2009

Mixed polyelectrolyte brushes with a composition gradient were used as a platform for fabrication of stimuli-responsive command surfaces to control the generation of concentration gradients of adsorbed protein molecules. Switching between homogeneously adsorbed protein layers and adsorbed layers with protein concentration gradients was achieved by changing the pH of protein aqueous solutions. Protein adsorption and the direction of the adsorption gradient were tuned and also turned off and on or reversed by tuning the proton concentration in the pH range 4.0–8.6.
Formation of tethered bilayer lipid membranes probed by various surface sensitive techniques
Authors: Vockenroth Inga K. , Rossi Claire , Shah Muhammad Raza , Köper Ingo
Published: June 2009

Tethered bilayer lipid membranes are promising biomimetic architectures. Their formation has been investigated using four different surface sensitive techniques, including optical, acoustic, and electrical methods. The lipid bilayers are built in a two-step procedure; the proximal layer is formed by self-assembly and is then completed to a bilayer by fusion with small vesicles. The different technical approaches revealed specific aspects of the layer formation processes, namely, first a fast adsorption process followed by a longer rearrangement period. Similar phenomena have been observed for the vesicle fusion process. The results allow for a more controlled assembly protocol for the preparation of highly insulating lipid membranes.