bluuebunny/crossref_metadata_2025 huggingface dataset:
Theory of Photoacoustic Characterization of Thermophysical Properties of Multilayered Nanofilms
Authors: Hu Hanping , Zhang Wei , Xu Jun , Dong Yi , Xu Xianfan
Published: June 2009

In this work, the use of the photoacoustic technique for probing thermophysical properties of multi-layered nanofilms is explored. In the photoacoustic measurement of nanofilms, the thermal diffusion length must match with the thickness of the thin film, and the modulating frequency of the incident light should be much higher than usual so that to enhance the thermal-mechanical coupling and the spatial waviness of photoacoustic signal in both photoacoustic cell and sample itself. The current photoacoustic technique cannot fulfill the requirement of measuring thermophysical properties of multi-layered nanofilms. In present study, we develop a general photoacoustic model which takes thermal, mechanical, and optical properties, the geometry of a multilayer film, as well as the thermal contact resistances between layers into consideration. The frequency of the photoacoustic effect is extended to the ultrasonic region. The possibility of taking advantage of the resonance in the photoacoustic cell to overcome the decrease of the photoacoustic signal with the frequency increase is also explored. It is suggested that at high frequencies, the photoacoustic signals are obtained close to the resonance peak, which also contains the information of material’s properties. Resonance frequencies, sensitivity and the frequency range with the highest sensitivity for different types of materials are analyzed. As an example, calculations of the photoacoustic signals of nanofilms of SiO2 and Ni show that increasing the frequency can improve the precision and accuracy of the photoacoustic measurement, and the photoacoustic technique is promising for depth-profiling of thermophysical properties of multi-layered nanofilms.
Microfluidic System Simulation Including the Electro-Viscous Effect
Authors: Rojas Eileen , Chen C. P. , Majumdar Alok
Published: June 2009

This paper describes a practical approach using a general purpose lumped-parameter computer program, GFSSP (Generalized Fluid System Simulation Program) for calculating flow distribution in a network of micro-channels including electro-viscous effects due to the existence of electrical double layer (EDL). In this study, an empirical formulation for calculating an effective viscosity of ionic solutions based on dimensional analysis is described to account for surface charge and bulk fluid conductivity, which give rise to electro-viscous effect in microfluidics network. Two dimensional slit micro flow data was used to determine the model coefficients. Geometry effect is then included through a Poiseuille number correlation in GFSSP. The bi-power model was used to calculate flow distribution of isotropically etched straight channel and T-junction microflows involving ionic solutions. Performance of the proposed model is assessed against experimental test data.
A High Sensitivity Piezoresistive Pressure Sensor
Authors: Mian Ahsan , Law Jesse
Published: June 2009

In the current investigation, the piezoresistive effect in a van der Pauw (VDP) stress sensor subjected to biaxial stress was considered. The VDP resistance equations were combined with the silicon piezoresistivity equations to yield relations for the change in resistance of a VDP sensor in terms of the applied state of stress. Then the sensitivity of the VDP sensor to biaxial stress was determined analytically and simulated numerically. The biaxial stress states considered were those for a circular diaphragm under pressure. The numerical calculations involved the use of anisotropic conduction based simulations, implemented in MATLAB using the finite difference technique. The VDP sensitivities to biaxial stress were compared to the sensitivity for the conventional piezoresistive stress sensor. It is observed that the theoretical (based on analytical and numerical results)pressure sensitivity of the new VDP sensor is about three times greater than the conventional counterpart. Analysis was performed for both p-type and n-type Silicon. It is determined that the angle of the VDP sensor with respect to the Silicon crystallographic axes can and should be optimized, depending on Silicon dopant, and the optimum orientation angles are determined.
Engineering Gas Sensors With Aerosol Nanocrystals
Authors: Lu Ganhua , Zhu Liying , Hebert Stephen , Jen Edward , Ocola Leonidas , Chen Junhong
Published: June 2009

Rutile tin oxide (SnO2) is a wide band gap (3.6 eV at 300K [1]) n-type semiconductor material. It is widely used as sensing elements in gas sensors [2]. The sensing mechanism is generally attributed to the significant change in the electrical resistance of the material associated with the adsorption/desorption of oxygen on the semiconductor surface [3]. The formation of oxygen adsorbates (O2− or O−) results in an electron-depletion surface layer due to the electron transfer from the oxide surface to oxygen [4]. Recent studies [5, 6] have shown that use of tin oxide nanocrystals significantly improves the dynamic response and the sensitivity of sensors since the electron depletion may occur in the whole crystallite. Here we report on the fabrication and characterization of a miniaturized gas sensor based on tin oxide nanocrystals. A simple, convenient and low-cost mini-arc plasma source is used to synthesize high-quality tin oxide nanoparticles in aerosol phase at atmospheric pressure. The nanoparticle sensor is then fabricated by electrostatic assembly of product tin oxide nanoparticles onto e-beam lithographically patterned interdigitated electrodes. The microfabricated nanoparticle sensor exhibits good sensitivity and dynamic response to low-concentration ethanol vapor and hydrogen gas diluted in air.
Modeling Gaseous Flows Through Micro- and Nano-Channels
Authors: Sun Hongwei , Faghri Mohammad
Published: June 2009

The overall object of this paper is a systematic study of gaseous flows in two-dimensional micro- and nano-channels in terms of the effects of compressibility, rarefaction, and surface roughness which are usually neglected in conventional flow analysis, using direct simulation Monte Carlo (DSMC) method. The flows are mainly in slip and transition regimes that are often encountered in Microelectromechanical Systems (MEMS), Nanoelectromechanical Systems (NEMS), and other microscale devices in diverse fields like molecular biology, space propulsion, and particle physics. For the effect of compressibility, two flows with same outlet Knudsen number (Kn) but different pressure drop ratios (case1:1.3, case2: 4.5) were simulated. It was found that high pressure drop flow (case2) show a 15% higher friction coefficient than that of a fully developed flow while the low pressure drop flow (case1) is consistent with incompressible flow prediction. The inspection for the velocity profile development shows that when pressures drop increase along the channel, the center-line velocity become flatten and the velocity gradients near the wall are higher compared with parabolic velocity profile. The effect of rarefaction was studied by simulating two nitrogen flows with low-pressure drop ratio (= 1.9) but different Kn numbers. (case3: 0.043, case4: 0.083). The pressure distribution, velocity profile, local friction coefficient are checked. The comparison with continuum flow theory (fRe = 24.0) shows that the rarefactions reduce the friction coefficient by 22% and 36% for case3 and case4, respectively. Apparent velocity slips along the channel wall exist for these flows. A locally fully developed model based on local velocity slip and fully developed assumptions predicts the friction coefficient accurately but fails in transition region where the Kn is over 0.1. Two important ratios are investigated for surface roughness effect in micro- and nano-channel flows: relative roughness and distribution of roughness. The DSMC results show that the surface roughness has more profound effect for a lower Kn number microchannel flow. The roughness distribution also plays a very important role in microchannel flows. The denser the roughness distribution, the higher friction coefficient. The future work will focus on flows in free-molecular flow regime and three-dimension geometries.
Reliability Assessment of MEMS Structure of Su-8 Thin Film
Authors: Park Jun-Hyub , An Joong-Hyok , Kim Yun-Jae , Lee Hak-Joo , Roh Hee Yuel , Kim Sang-Hyun
Published: June 2009

This paper describes new test method for obtaining static and dynamic characteristics of thin film and reliability evaluation method on MEMS device with thin film. The Su-8 is often used in micro-electro-mechanical systems devices. Durability should be ensured for such devices under cycling load. Therefore, with the proposed specimen and test procedure, tensile test was performed to obtain mechanical properties. The specimen was made with dimensions of 1000μm long, 9 and 11 μm thickness, and 3 kinds of width, 50, 100 and 150μm. Behaviors of Su-8 have the 3 kinds of stress-strain curves. The mechanical characteristics of Su-8 were multiple, showing characteristics of brittle and ductile material and polymer. It was found that the mechanical properties of Su-8 did not have any effect on thickness. High cycle fatigue test was performed to obtain probability of failure at a given stress. We found that fatigue life of Su-8 was very susceptible to stress level and then strength-stress model was suitable for the assessment of durability of MEMS structure under cycling load.
Design and Simulation of Quartz Tuning Fork Temperature Sensor
Authors: Xu Jun , You Bo , Li Xin
Published: June 2009

In order to optimize the design of quartz tuning fork temperature sensor, finite element method (FEM) is applied to model optimum tuning fork geometry, tine tip and tine surface electrode shape and thickness with a resonance frequency close to 32 kHz and a series resistance value of 40 kΩ as design targets. This type of sensor designed with a new ZYtw-cut is proved that working at flexural vibration mode was better than at the others modes. Precise temperature versus frequency analyses of resonators have been carried out and Least Mean Squared (LMS) curve fit algorithm is applied to compute the temperature values quantitatively. The results obtained from the experimental investigations show the method which synthesizes many factors to design quartz tuning-fork temperature sensor. Using ZYtw-cut can bring the temperature coefficient up to 70ppm/(degree C) and make power consumption lower. The temperature sensor based on quartz tuning-fork thermo-sensitive resonator is mounted in a standard holder for use from −30 degree C to 160 degree C with an accuracy of 0.05 degree C and a high resolution of 0.001 degree C. It is proved that it is possible to construct a miniature quartz tuning-fork temperature sensor with high sensitivity and small non-linearity.
Microscale Vapor Bubble Interactions During Subcooled Nucleate Boiling on a Heated Wire
Authors: Zhang Lu , Christopher David M.
Published: June 2009

Bubbles have been observed moving along heated wires during subcooled nucleate boiling as they are driven by Marangoni convection around the bubbles. This paper presents more detailed observations of the vapor bubble interactions and moving bubble behavior during subcooled nucleate boiling on a heated microwire. The experimental results show that moving bubbles coalesce or rebound from other bubbles and that bubbles hop on the wire. These observations show how bubble interactions significantly affect nucleate boiling heat transfer rates and how Marangoni flow plays an important role in microscale nucleate boiling heat transfer mechanisms.
Simulation and Test of a Doubly Decoupled Lateral Axis Gyroscope
Authors: Liu Xuesong , Lv Bo , Yang Zhenchuan , Ding Haitao , Yan Guizhen
Published: June 2009

A novel doubly decoupled bulk micromachined lateral gyroscope, proposed in our former work, can efficiently suppress the undesired mechanical coupling, while remaining symmetric in structure. Both theoretical simulations and experiments are carried out to analyze the decoupling property of this gyroscope. The simulated results show that the driving and sensing mode frequencies are 3.821 kHz and 3.956 kHz, respectively. Furthermore, the displacements of the driving mode and sensing mode are also simulated by ANSYS™. In driving mode, simulation result shows that the mechanical coupling from the driving mode to sensing mode is 8%. Similarly, in sensing mode, the mechanical coupling from the sensing mode to driving mode is 0.9%. Micro Laser Doppler vibration meter is employed to detect mechanical coupling in the sensing mode. The test result is about 2%, close to the simulated value.
Dielectrophoretic Separation Motion of a Particle From Electrolyte Solution in Micro-Channel
Authors: Chen Zhenqian , Shi Mingheng
Published: June 2009

Dielectrophoresis (DEP) based on the processes of particle separation and particle detection in micro-channel is one of the most important operations required for many lab-on-a-chip devices. To understand the mechanism of the DEP, a theoretical analysis of dielectrophoretic separation motion of a spherical particle in a rectangular micro-channel filled with an aqueous electrolyte solution is presented in this paper. The dimensions of micro-channel are 100 μm in width and 200 μm in length. In this study, driven forces on the particle are analyzed in detail. At the gravitational direction, it is assumed that the density of the spherical particle is higher than that of the solution, and thus the gravitational effect is considered coupled with the buoyancy force and the electric double layer interaction force as well as the van der Waals force. Both the DEP force and the viscous friction force drive the particle separation motion from the solution in micro-channel. The particle separation distance of the particle from the bottom wall by the action of these forces and its motion behavior are analyzed and calculated. The DEP motion along the channel in an applied non-uniform electric field is simulated. Effects of particle’s size, electrolyte solution concentration and applied electric field strength on the DEP motion are discussed.
Parametric Study for the Phase-Change Process of Liquid Flow With Microencapsulated PCM Particles in Microchannels
Authors: Hao Yingli , Lu Jinli
Published: June 2009

The phase-change process of phase-change material (PCM) is the key for the microencapsulated phase-change material (MCPCM) particle suspension flow to enhance the heat transfer, enlarge the capability of thermal energy transportation and employ in the engineering application. In the present paper, the parametric study for the phase-change process of the MCPCM suspension flow in a heated microchannel is carried out using the model and numerical technique developed in previous works. The effects of particle volume fraction, Reynolds number, and wall heat flux on the phase-change process have been numerically analyzed. It is found that the benefits of enhancing heat transfer and reducing wall temperature by employing the MCPCM particle are limited to the melting region. There exists a constant wall temperature region in the melting region under the certain condition. The trend of influence of particle volume fraction, Reynolds number, and wall heat flux on starting location, length, wall temperature, and average heat transfer coefficient in the constant wall temperature region is revealed. The numerical simulation may guide the optimal condition of design and operation to utilize the MCPCM suspension flow not only for enhancing the convection heat transfer and enlarging the thermal energy transportation capability, but also for controlling the micro-device temperature uniform.
A Study for Flow Characteristics of Liquid Slip Flow in Rectangular Microchannels
Authors: Jiang Jie , Hao Yingli , Lu Jinli
Published: June 2009

Nowadays, there has been great interest in micro- and nano-applications. Understanding the flow and heat transfer in microscale is useful. The primary goal of this investigation is to reveal the flow behavior in microchannels. The deionized water flow in a microchannel was experimentally investigated. The pressure drops were measured under the conditions of different Reynolds numbers. The friction factors were obtained based on the experimental measurements. The friction factors deviate significantly from the conventional theory. A series of numerical simulation was also carried out to explore the mechanism of the deviation in the present paper. The numerical simulation adopting the slip boundary condition shows the numerical results coincide with the experimental results very well. The velocity slip was obtained based on the comparison with the experimental results. By introducing the slip length Ls, the velocity slip of water flow in the microchannel can be characterized. The velocity slip increases with the increase of the inlet velocity and the slip length increases with the increase of the shear rate. The linear Navier boundary condition breaks down when the shear rate reaches a critical value. A correlation between the velocity slip and the inlet velocity based on our experimental measurements and numerical results was obtained.
Multi-Scale Observation of Microscopic Protrusion Topography of Diamond Grinding Wheel
Authors: Xie J. , Tian Z. L.
Published: June 2009

Multi-scale evaluation of microscopic grit protrusion topography on dressed wheel surface was conducted with reference to diamond grit protrusion height, its distribution coefficient, active grit protrusion number, grit pull-out number and protrusion fractal dimension. The aim is to evaluate dressing performance of diamond grinding wheel by the use of grit protrusion topography. First, dressing experiments of metal-bonded #40, #80 and #120 diamond grinding wheels were conducted with reference to different dressing parameters such as the depth of cut and moving speed. Second, grit protrusion height was measured and its distribution coefficient was analyzed. Then, the microscopic observation of grit protrusion feature was conducted to evaluate dressing results. Finally, fractal dimension was employed to analyze cutting edge integrality of diamond grit protrusion. The experimental results and theoretical analyses showed that average protrusion height is about 1/3 of diamond grit size and mainly depends on the depth of cut. The distribution coefficient of protrusion height can be used to evaluate the trimness of grit protrusion heights and active grit number. In addition, the fractal dimension of grit protrusion shape can display grit cutting edge integrity and its crack feature, namely the less fractal dimension, the better grit protrusion integrity and the better dressing result.
Characterization of a Micropump Actuated by Ternary TiNiCu Shape Memory Thin Films
Authors: Zhang Huijun , Qiu Chengjun
Published: June 2009

Thin film SMAs have the potential to became a primary actuating mechanism for micropumps. In this study, a micropump driven by TiNiCu shape memory thin film is designed and fabricated. The micropump is composed of a TiNiCu/Si bimorph driving membrane, a pump chamber and two inlet and outlet check valves. The thickness, surface morphology and phase transformation property of TiNiCu film have been characterized by scanning electron microscope (SEM), atomic force microscopy (AFM), differential scanning calorimeters (DSC). Driving capacity of TiNiCu/Si biomorphic driving membrane has been investigated. The film surface shows a smooth and featureless morphology without any cracks, and the hysteresis width ΔT of TiNiCu film is about 10 °C. By using the recoverable force of TiNiCu thin film, the actuation diaphragm realizes reciprocating motion effectively. Experimental results show that the micropump driving by TiNiCu film has good performance, such as high working frequency, stable driving capacity, and long fatigue life time.
Spatio-Temporal Mapping of Transient Electric Fields With an Ultrafast Scanning Tunneling Microscope
Authors: Lan Tian , Ni Guoqiang
Published: June 2009

In this paper, we report experimental results of spatio-temporal mapping of electrical transients scanned in strip direction with an ultrafast scanning tunneling microscope. The transients are pumped by ultrashort laser pulses with duration of 100 fs and a wavelength of 800 nm on a coplanar strip line sample. The signals on a coplanar strip line were measured in both contact and non-contact mode. The resolved transient signal showed a full width at half maximum (FWHM) pulse width of 1.2 ps. The pulses propagate along the CPS at a speed of about 2/3 of the light velocity. The spatial resolution image of the gold surface on the transmission line acquired with the tip by the STM under ambient condition has a resolution on the order of 20 nm.
Tensile Properties and Dislocation Strengthening of CP-Ti Processed by Equal-Channel Angular Pressing at 723K
Authors: Xu Xiaojing , Zhang Xuefeng , Cao Jinqi , Chen Kangmin , Pan Li
Published: June 2009

In present study, equal channel angular pressing (ECAP) of a quenched commercially pure titanium (CP-Ti) (grade 2) has been successfully performed at 723 K with an imposed equivalent normal strain of about ∼0.5, and its tensile properties and dislocation strengthening was investigated. A high yield strength of ∼680 MPa (36% higher than that of the unECAPed CP-Ti) in terms of CP-Ti has been observed. In addition to the strengthening, this processing allows the ECAPed CP-Ti have a high level of tensile ductility (∼30%). The dislocation strengthening contribution was estimated by using Taylor equation, where the dislocation density was calculated in terms of the value of the coherent diffraction domain size and the lattice micro-strain, which were obtained from XRD line broadening analysis. This theoretical analysis illustrates that ECAP-resulted dislocation make a strengthening contribution of about ∼34.9% for the improvement in strength.
Simulation of Fluid Mixing in Microchannel Under Heterogeneous Zeta-Potential Effect by Lattice-Boltzmann Method
Authors: Kang Jinfen , Suh Yong Kweon , Heo Hyeung Seok
Published: June 2009

In this study, we use the lattice Boltzmann method to implement 2-D and 3-D numerical simulations to investigate the electrokinetic effect on the fluid flow and mixing in a rectangular microchannel. Zeta-potential is employed as the main factor representing the electrokinetic effect. The numerical simulations aim at two new designs of electrode distribution in the microchannel. One uses the periodically distributed rectangular electrodes on both sides of the walls of the microchannel, in which 2D and 3D simulations were implemented with time periodic application of the electric potential on the electrodes. In another model, periodic array of trapezoidal electrodes were attached on the bottom walls, and 3D simulation was carried out with constant zeta-potential on the electrodes. The simulation results of the second design model by LBM have been compared with those obtained by CFX and good agreement was obtained. Through the parametric studies for both designs, it was shown that there exists an optimum parameter value leading to the best mixing performance.
Nanofluids Containing Hybrid Sphere/Carbon Nanotube Particles
Authors: Han Zenghu , Yang Bao , Kim S. H. , Zachariah M. R.
Published: June 2009

Previous studies on nanofluids have focused on spherical or long-fiber particles. In this work, a new type of complex nanoparticles—hybrid sphere/carbon nanotube (CNT) particle, consisting of numerous CNTs attached to an alumina/iron oxide sphere—is proposed for applications in nanofluids. In such hybrid nanoparticles, heat is expected to transport rapidly from one CNT to another through the center sphere and thus leading to less thermal-contact-resistance between CNTs when compared to simple CNTs dispersed in fluids. CNTs have an extremely high thermal conductivity, but thermal resistance between the CNTs and the fluid has limited their performance in the nanofluids. The proposed hybrid sphere/CNT particles are synthesized by a spray pyrolysis followed by catalytic growth of CNTs. The spheres are about 70 nm in diameter in average, and the attached CNTs have a length up to 2μm. These hybrid nanoparticles are dispersed to poly-alpha-olefin with sonication and a small amount of surfactants to form stable nanofluids. The thermal conductivity of the fluids has been measured by a 3ω-wire method over a temperature range 10–90°C. The results indicate that the effective thermal conductivity of the fluids is increased by about 21% at room temperature for particle volume fractions of 0.2%.
Properties of Nanosized Tin Oxide Thin Film Prepared by Reactive Magnetron Sputtering
Authors: Liu Xiao Di , Zhang Dacheng
Published: June 2009

Nanosized tin oxide thin films were fabricated on silicon and quartz glass substrates by direct current reactive magnetron sputtering method, and then were calcined at different temperatures ranging from 400°C to 900°C. The results analyzed by X ray photoemission spectra (XPS), scanning electron microscope (SEM), Spectroscopic ellipsometer, Powder X-ray diffraction (XRD), and HP4145B semiconductor parameter analyzer measurements show that the sample with quartz glass substrate and calcinated at 650°C possesses better properties and suitable to be used in our gas sensor.
A Study on the Electrodeposited Cu-Al2O3 Composites Coating With Laser Treatment
Authors: Fan Hui , Huang Yinhui , Tian Zongjun , Liu Zhidong , Chen Jinsong
Published: June 2009

One kind of jet electrodeposition machine with multi-spindle function has been successfully designed and launched. With the jet electro-deposition device, Al2O3 particles of average size 30 nm were co-deposited with Copper on a steel substrate using a Watts bath at 50°C and the compound layer was processed by laser in order to make the layer clad on the substrate in a well binding force. The compound layer’s microstructure was examined by scanning electron microscopy (SEM), the mechanical properties of the coated steels were examined with hardness and tensile tests. The effects exerted by the current density, weight percentage of Al2O3 in electrolyte and the presence of laser treatment was investigated respectively. It shows a relatively small current density and a certain of Al2O3 particles have a positive effect on both surface morphology and coated material’s mechanical behavior. In addition, result also shows the coating processed by laser, attained a hardness up to 820 HV, which is considerably increased than substrate.
Transition From MEMS Technology to Nanofabrication
Authors: Glinsner T. , Lindner P. , Kettner P. , Kirchberger H.
Published: June 2009

The successful commercialization of Micro-Electro-Mechanical Systems (MEMS) from R&D to off-the-shelf products and systems has evolved from laboratory research to reliable and low cost industrial processing methods over the past 20 years. Standardization, infrastructure, roadmaps and industrial associations have been deemed key contributors for a successful transition and adaptation of microelectronics fabrication techniques to a specific nature of manufacturing MEMS devices resulted in turn key solutions for low cost, high yield and high volume wafer level processing. The need for smaller feature sizes as well as low cost manufacturing solutions has lead to significant improvements of the classical optical lithography in the past two decades following Moore’s law. Alternative patterning techniques are under development worldwide for producing patterns in the nm-range. There are similarities between MEMS and Nanofabrication requirement that allow for transitioning standardized and reliable processing technology from wafer bonding to hot embossing and from wafer level packaging to μ-CP and UV-based Nanoimprint Lithography.
A Bulk Micromachined Si-on-Glass Tunneling Accelerometer
Authors: Miao Min , Hu Qifang , Hao Yilong , Dong Haifeng , Zhang Haixia
Published: June 2009

A bulk micromachined tunneling accelerometer on Pyrex 7740 substrate is reported in this paper, which is intended for the applications in highly sensitive inertia measurements, such as those in microgravity environments and self-contained navigation. The tunneling tip is defined by an isotropic wet etching followed by a maskless wet thermal oxidation for the sharpening of the tip. Unlike the process ever reported by other facilities, an ICP etching on the side of the Si wafer with the tip is utilized to partially define the suspension and the proof mass before the anodic bonding of the Si wafer with the glass substrate, and an addition maskless ICP etching is used to release the whole movable structure after the bonding. Fabricated samples have displayed the effectiveness of the process proposed, which is relatively simple and may guarantee the yield of mass production. The theoretical analysis and design of the closed loop architecture of the device are demonstrated. Capable of sensing out-of-plane acceleration, this device has demonstrated a high resolution of 0.015mg/rtHz (@ 1∼100Hz) and a nonlinearity of less than 1% over ±1g input range.
Study on the Damage of Magnetic Recording Media
Authors: Zhang Peng , Li Jibin , Wang Hongzhi , Zeng Qigao , Zhang Xiaohui
Published: June 2009

A series of friction and wear test with different damage degrees were made on a group of floppy disks. Through investigating the change situations of recording characteristics of magnetic recording media before and after test as well as combining the Nano-tribology researching method, the critical area that the recording characteristics of magnetic recording media turning to failure was found out. Finally, descriptions and tokens of damages in the test were discussed.
Hybrid Integration in Photosensitive Glass Using 3D Femtosecond Laser Micromachining and Its Commercial Potential
Authors: Cheng Ya , Xu Zhizhan
Published: June 2009

By shrinking a roomful of laboratory equipments and packing them into a palm-size chip, single Lab-on-a-chip devices are capable of performing a variety of chemical and biological analyses with reduction of reagent consumption, waste production, analysis time and labor cost. However, difficulties in packaging and assembly have been major challenging issues in the manufacture of Lab-on-a-chip devices. To tackle this problem, we recently combined the 3D femtosecond (fs) laser microfabrication technique and the multifunctionality of a photosensitive glass called Foturan. This development enables us to form various true 3D hollow microstructures inside or on the surface of Foturan glass with one continuous processing. Using this technique, a variety of micro-chemical reactor structures, including microchannels, microchambers, and microvalves, have been fabricated inside Foturan glass with an approximate spatial resolution of 10μm. Since the microstructuring of Foturan glass by fs laser is a non-ablative photochemistry processing, the fabricated internal surface is smooth and free of debris and cracks. The smooth surfaces can thus be used as microoptical elements to effectively reflect/deflect light beams. For the purpose of further smoothening the etched internal surface, we applied an additional annealing to the samples after etching by which the average roughness was brought down to ∼0.8nm on the laser scanned surface. Thus, we are able to fabricate microoptical mirrors, micro-beam splitters, freestanding optical fibers, and microoptical lenses in the glass. We have also demonstrated the functions of all these structures using a He-Ne laser. Functional micro-devices such as microfluidic dye lasers were successfully fabricated by integrating the microoptical and microfluidic components inside the glass, and lasing action was confirmed by analyzing the emission spectra at different pumping powers. The commercial potential of this technique is also discussed in this paper.
Numerical Analysis the Strain Distribution of GaN/AlN Self-Organized Pyramid Quantum Dot
Authors: Liu Yumin , Yu Zhongyuan
Published: June 2009

Based on the three-dimensional finite element approach, we investigate the strain field distribution of the GaN/AlN self-organized quantum dot. The truncated hexagonal pyramid quantum dot that has been found in experiment is adopted as the physical model in our simulation. The material elastic constants parameters used in this paper are of wurtzite structure, and there are five independent elastic constants. In dealing with the lattice mismatch, we employ a three-dimensional anisotropic pseudo-thermal expansion. We compare the calculated results with that calculated by Green’s function theory, in which many assumptions are made, and prove the correctness of our results. The strain distributions of the equal strain surface three-dimensional contour plots of the six strain components are given. Finally, the anisotropic characteristics of the GaN/AlN quantum dot material are discussed, the results demonstrate that the position of the elastic strain energy density minimum position is just located above the buried quantum dot and have no influence on the thickness of the capping layer. So the anisotropy has no obvious influence on the vertical alignment of post-growth of the next layer of quantum dots. Our model does not adopt the assumptions used in the Green’s function approach, so better reliability and precision of results are expected.
Analytic Calculation About the Strain Distribution of Any-Shaped Self-Organized Quantum Dot
Authors: Liu Yumin , Yu Zhongyuan
Published: June 2009

The strain distribution of quantum dots is analytically calculated using the Green’s function technique; the general expressions for any shaped quantum dot are derived. As examples, this method is applied to cube, pyramid column, and taper-shaped quantum dot. Our expressions are correct comparing with the calculated results by finite element method and finite difference. This approach is very powerful and can be applied to any-shaped quantum dot, especially this method can directly used in the calculation of electronic structure of quantum dot by the envelop function approximation or plane wave expansion methods, because the analytic expression can exactly calculate the strain at any position. In the paper, we give the strain distribution of four types of shaped quantum dot, and some comparisons are given with the results calculated by the finite element method.
Two Different Types of Axially-Grooved Heat Pipes and Thermal Performance Comparison
Authors: Chi Yong , Tang Yong , Jiang Le-Lun , Wan Zhen-Ping , Pan Min-Qiang
Published: June 2009

Heat pipes have been widely applied to the cooling of microelectronics chips at present. In this paper, to conduct a comparative study on heat pipe performance with different groove structures, two types of axially-grooved heat pipe were manufactured by spinning and secondary broaching respectively. The heat pipe A formed by spinning has homogeneous 55 U-shaped grooves on the inner wall. The grooves with depth of 220μm, width of 200μm and groove angle of 15° are smooth. While the inner wall of the heat pipe B fabricated by secondary broaching is scored and the grooves are heterogeneous. The comparison of heat transfer performance and start-up of two heat pipes are analyzed and investigated under different orientations and heat loads. Experimental results show that the heat pipe formed by spinning has a stronger level of heat transfer capabilities than heat pipe formed by secondary broaching. The maximum heat transfer rate for the heat pipe formed by spinning is almost 70Watts, while the one for the heat pipe fabricated by secondary broaching is only 20Watts. The minimum thermal resistance of the heat pipe A and B was 0.020°C/W and 0.068°C/W respectively. At positive inclination angles in gravity-assisted condition, the thermal performance of both two heat pipe have not obvious difference with at horizontal orientation. But at negative inclination angles in anti-gravity condition, the gravity will play an important role on grooved heat pipes.
Modelling of Flow Uniformity Among Non-Uniform Cross-Section Microchannels
Authors: Pan Minqiang , Tang Yong , Zhang Yihong , Zhou Wei
Published: June 2009

A model of non-uniform cross-section microchannels for realizing flow uniformity is developed in this work. For easy fabrication of microchannels, only the microchannel widths are changed while the thicknesses remain unchangeable in this model, and the relation of the widths of two adjacent microchannels has been established. A specific case is illustrated to study the influence of structural parameters on the microchannel widths. Result indicates that almost all the microchannel widths have symmetrical distribution. The maximum value appears near the edge while the minimum value in the middle microchannel. For all the structural parameters, the rake angle of manifold has a considerable effect on the microchannel width, and the preset value of microchannel width shows a slight influence.
Control Over Air Gap of Active Magnetic Bearing Based on DSP
Authors: Ren Shuangyan , Bian Chunyuan , Wang Zhiqiang , Liu Jie
Published: June 2009

On the basis of a mathematic model, a digital control system based on digital signal processor (DSP) TMS320LF2407A is designed. The design plans of hardware and software are produced. A control algorithm combined with PID control with detached integral and PID control with variable arguments (three regions) is presented. Also, simulations and experiments are implemented. The results show whether there are or not any kinds of disturbances, the rotor can always be levitated near the balance position stably with the designed controller. The AMB system of digital control has advantages such as high stability, rapid response, small overshoot, low noise, high control precision and so on, which meet the requests of AMB control properties.
The Property of Ni-Fe Electrodeposits for MEMS
Authors: Zheng Xiao-Hu
Published: June 2009

This paper was focused on the composition controlling, coating microstructure and electromagnetic character of Ni-Fe deposit. The results indicated that the Ni-Fe deposit was bright and compact; the crystal-planes of the deposit were (111), (220) and (200). And the optimal process parameters to obtain Ni-20%Fe deposition was as following: FeSO4·7H20 concentration was 6g/L; PH value of the solution was 2.5; current density was 3.5 A/dm2; electrolyte temperature 55°C. The resistivity of deposit was about 30μΩ·cm, when the Fe(wt.%) ranged from 10% to 50% in the deposit. Electrodeposited Ni-20%Fe has a strong paramagnetism effect with the smallest remanence of 0.5 emu, The coercivity show a monotonic decrease with increasing Fe content in deposit, and the saturation magnetization was only 10% of that of the IJ85 permalloy, which proved that the electroformed Ni-20%Fe alloy has good electromagnetic property and could be used in MEMS actuator fabrication.
Optimization of Machining Parameters and Fabrication of Nanostructures Using AFM Anodic Oxidation
Authors: Yan Yongda , Sun Tao , Liang Yingchun , Zhang Jing , Yu Wei , Dong Shen
Published: June 2009

AFM anodic oxidation has been an effective method for fabricating nanostructures. It has been applied in the fundamental research of nanoelectronics. Actually, AFM anodic oxidation is a chemical reaction process influenced by co-effects of many factors. Effects of synthesis roles of all factors on dimensions of oxide nanostructures and machining efficiency are major issues for the combination of AFM anodic oxidation technique and conventional micromachining techniques to fabricate electronics. Therefore, to fabricate oxide nanostructure effectively, orthogonal test was employed to study effects of three factors: bias voltage, machining velocity (or pulse interval) and the cantilever deflection on dimensions of nanostructures. Results showed that cantilever deflection had a significant effect on dot dimensions and had little effect on line dimensions. Based on optimization of nanostructure dimensions and machining efficiency, the optimal machining parameters (bias voltage, machining velocity or pulse interval and the cantilever deflection) on the surface of N-Si (111) were achieved under the conditions of humidity of 54% and at temperature of 23° C. Using the optimal machining parameters, regular nanostructures: lattice, annulus and complex Chinese words, were fabricated based on a novel AFM-based nanomachining system integrated a precision stage. The AFM tip was still and the precision stage moved the sample. The shortcoming of low repeatability positioning accuracy of AFM Piezo scanner during machining was eliminated. A larger machining scale with high accuracy can be realized on this system by the dot array-style fabricating method and the vector-style fabricating method.
Research on Micro Accelerometer Array
Authors: Xiong Jijun , Mao Haiyang , Zhang Wendong , Xu Dong , Guo Tao
Published: June 2009

In a physical process, there might be more than one acceleration to be measured, but a micro accelerometer of a certain testing range can hardly satisfy the measurement requirement. In this paper, a micro accelerometer array with four testing ranges, namely, 0∼100g, 0∼500g, 0∼1,000g and 0∼2,000g, is designed and fabricated. In addition to the design and fabrication process, the protection for the array elements on the condition of overload is described in detail. From the static and dynamic measurement results, it is known that the array has linearity smaller than 2.5%, what’s more, it has quite good frequency response characteristics. The experimental results demonstrate that the array can be used for the measurement of a physical process with multi-acceleration.
Micro-Device for Rapid Separation of Suspensions for Use in Micro-Total-Analysis-Systems (μTAS)
Authors: Gregoratto Ivano , McNeil Calum J. , Reeks Michael W.
Published: June 2009

A planar micro-device capable of rapidly separating large volumes of dilute suspensions was designed and modelled using a commercial CFD package. The device consists of a single planar Archimedean spiral micro channel with a bifurcation at the exit. The device exploits small inertial and hydrodynamic differences between particles of dissimilar size, which arise as the sample is rapidly pumped through the device. The channel length and location of the bifurcation were found to affect the separation achievable by the devices. Devices of varying geometries were fabricated using conventional silicon micro fabrication processes and were tested by flowing dilute aqueous suspensions of polystyrene particles (diameters of 1μm, 8μm and 10μm) through the devices at various flow rates. A 3.5 fold concentration enhancement of 10μm particles was achieved in the longer devices at flow rates of 2 ml/min, whereas the 1μm particles showed negligible concentration increases at similar flow rates. The device may be used as a sample preparation stage in a complex μTAS, where rapid, continuous concentration of dilute suspensions is often required.
Development of Micro Milling Machine and Experimental Study on Meso Scale Milling
Authors: Li Chengfeng , Lai Xinmin , Li Hongtao , Peng Linfa , Ni Jun
Published: June 2009

This paper develops a three-axis micro milling machine for manufacturing meso-scale components and products. This machine utilizes high-speed miniature spindle to obtain appropriate cutting velocities, and three precision linear stages with 50 nm feed resolution to supply the relative motion. The PMAC2 controller is used to control three axes simultaneously, and a piezoelectric dynamometer is mounted on the X-Y stages to measure three-dimensional cutting forces for the real-time measurement and feedback. More than 200 cutting experiments of end milling operations are performed on the developed machine. When the machined feature ranges at meso scale, the characteristics and phenomena in milling process will heavily differ from those of conventional scale milling due to the size effects. The critical differences at meso scale arise from the breakdown of the assumptions of negligible edge radius effects. The roundness of cutting edge and the runout of spindle have a crucial impact on the chip formation process and the characteristics of cutting forces. The roundness of cutting edge also induces the existence of the minimum chip thickness and the intermittency of the chip formation at a low feed per tooth.
Theoretical Investigation on Nano TiO2 Photocatalytic Oxidation of VOCs
Authors: Yu Huili , Zhang Kaili , Rossi Carole
Published: June 2009

Controlling mechanisms for photocatalytic degradation of volatile organic compounds by nano TiO2 catalyst are found to be mass transfer, diffusion, adsorption and photochemistry. A mathematical model for the degradation process is developed by incorporating these mechanisms in a plane plate air purification physical model. Finite difference method is employed to solve the governing equation and boundary conditions. The computation results are validated using the data from experiments. The model is then used to investigate the effects of some key factors on the degradation of formaldehyde including UV light intensity, UV light attenuation coefficient, adsorption, catalyst thickness, and flow rate.
Precisely Controlling Assembly Angle of Surface Tension Powered Self-Assembly for MEMS Microstructures
Authors: Pan Kai-Lin , Yan Yi-Lin , Zhou Bin
Published: June 2009

How to integrate the microstructures which are made by various micro manufacturing methods into a functional system or device is the key to the application of MEMS technology. Solder self-assembly is based on surface tension with the properties of “self-organization”, low cost, batch processes and the compatibility with surface mount technology, which makes it be a challenging alternate technique. Solder self-assembly is based on the principle of surface energy minimization of molten solder material. During the process of minimizing the surface energy, surface tension can pull the horizontal hinged or hingeless plate up to a particular angle to achieve the minimal system energy. Finite element method is applied in this paper. MEMS self-assembly three-dimensional dynamic simulation model is developed by SURFACE EVOLVER. First, the model in this paper dynamically simulate the angle change of hinged plate during the process of evolvement of solder; second, the comparisons among the results from the current model and those from analytical two-dimensional model and three-dimensional static model are carried out; third, through Design of Experiments (DoE) with the application of the current model, the influences of design parameters such as pad size, pad geometry, and solder paste volume to the assembly angle are compared and discussed. Through changing the pad size, pad geometry and solder paste volume in SURFACE EVOLVER model, the corresponding final assembly angel from dynamic three-dimensional models are obtained. The relationship between design parameters to the assembly angle is concluded by the application of statistical analyses. The final angle can be controlled more effectively through synthetically optimize these parameters. It can provide effective guidance to the practical manufacturing of MEMS. Further research should focuses on the MEMS self-assembly experiment to intensively understand the relationship between the pad sizes, pad position, solder paste volume, hinge position, lock position and intermetallic compounds and the final assembly angle.