bluuebunny/crossref_metadata_2025 huggingface dataset:
Poly(N-Isopropylacrylamide-Co-Methacrylic Acid) Micro/Nanoparticles: Formulation, Size Distribution and Use for Cu++ Adsorption
Authors: Wu Qinglin , Tian Peng , Cao Quang
Published: June 2009

Poly(N-isopropylacrylamide-co-methacrylic Acid (PNIPAAm-MAA) micro/nano-particles were formulated. The effect of monomer ratio, surfactant, and crosslinker contents on size/size distribution, phase transition behavior, and Cu2+ adsorption efficiency of the particles was investigated. The ionized MAA groups brought both temperature and pH sensitiveness to the PNIPAAm-MAA copolymer particles. As monomer ratio and crosslinker content increased and the amount of surfactants decreased, the particle size increased. The influence of the crosslinker content on particle size was less significant compared to the effect of monomer ratio and surfactants. When temperature increased, the particles tended to shrink and reduced their size to near or below 100nm. The Weibull distribution was successfully used to describe the diameter distribution of the nano-particles, whereas the lognormal was deemed not adequate for that purpose. The method of moments was used to predict parameters of the Weibull distribution. The Weibull parameters were recovered from diameter mean and variance, both of which were predicted from temperature. The distributions predicted from various temperatures for MAA/NIPAAm ratios of 0.05 and 0.10 showed trends similar to those in the data. Studies on chelation efficiency of the particles with Cu2+ ions showed that the amount of the Cu2+ ions adsorbed varied with temperature. Particle size played a very important role in the adsorption and nanoparticles greatly improved adsorption efficiency, compared with their micro hydrogel counterparts. The amount of adsorption increased with increase of MAA ratio in copolymers, but adsorption efficiency decreased with increased particle size. The high adsorption efficiency of metal ions by PNIPAAm-MAA polymer particles provides an effective technique for recovering metal ions (e.g., Cu2+) from wood treated with metal based preservatives.
A Bulk Micromachined Tunable Dual-Mode Microwave Bandpass Filter on Coplanar Waveguide
Authors: Miao Min , Bu Jingpeng , Zhao Liwei , Jin Yufeng , Zhang Yangfei
Published: June 2009

This paper proposes a bulk micromachined bandpass filter on 0.5mm-thick Pyrex glass, whose operation is based on the splitting of the odd and even degenerate mode in a dual-mode resonator, with the addition of a perturbation element. In such a way, a filter may require only half resonators of a traditional one, resulting in a more compact configuration over those ever reported. A 4%-bandwidth bandpass filter centered at 17GHz was designed. The square-ring-like coplanar waveguide (CPW) act as a dual-mode resonator, and an open-circuited stub attached to the inner corner of the square-ring acts as the perturbation element and dominates the filter bandwidth. The two bulk-micromachined switches for tuning are placed symmetrically along the diagonal line. Since the electrical length of CPW is extended after being loaded by capacitive switches, both the degenerate resonating frequencies and the filter mid-band frequency are shifted downward. Theoretical formulas are derived for various actuation states of all the switches. The filter performance is analysed also using finite-element fullwave tools. A frequency shift of 0.6GHz is seen which is close to 0.58GHz obtained from analytical solutions. Both the original and tuned state come with satisfying microwave performance, i.e. low passband insertion-loss (< 0.5dB) and return-loss (< −15dB) and high stopband rejection. It is also shown that the simulated result is in good agreement with theoretical solutions. The bulk microfabrication is shown to be much simpler than surface micromachining conventionally used for RF MEMS switches. Since the bridge skeleton is Si, thermal mismatch between all-metal bridge and dielectric substrate is avoided, and reliability at elevated temperature is guaranteed or at least greatly improved. Besides, the p++ doped Si line patterned simultaneously with the microbridges, can also be used as a DC biasing resistor, which can eliminate the additional steps to fabricate the resistive alloy line. The tested results of the fabricated switch samples are also shown. The device may be a good candidate for novel Ku-band inter-scientific satellite communication or wireless networking.
Study on Micro Thermoelectric Power Device With Various Micro Combustors
Authors: Song Ruiyin , Shen Menghong , Li Wei , Yang Canjun
Published: June 2009

Micro thermoelectric power device (MTPD) is used to supplying lasting and stable electric energy for Micro-electro-mechanical systems (MEMS). MTPD mainly includes three parts: micro thermoelectric generator, heat source and sink. To get highest energy density, simulation model for MTPD was built up and optimized. Heat source is an important part of MTPD and micro combustor is the ideal heat source for the device, which is used to supply lasting energy for MTPD. Based upon, several types of MTPD with different micro combustors was designed and tested. Some MTPDs with different design was tested. For example, MTPD with diffuse combustor and that of with premixed combustor, MTPD with quartz combustor and metal combustor, MTPD with liquid fuel and gas fuel, and comparison were done correspondingly. Through a series of experiments, some conclusions were drawn.
Multiscale Modeling of Protein Stretching in Nanofluidic Flows
Authors: Yang Zhi , Chen C. P. , Chen Z. J. , Chieng C. C.
Published: June 2009

The deformation of biological macroparticles such as DNA and proteins in a flow has been a subject of great important in the last decade due to the interest in single molecule analysis. In this paper, a multiscale numerical method was used to analyze deformation of biological macroparticles in uniform flows. To bridge the gap between huge scale differences between the protein dynamics (in Pico scales) and the underlying hydrodynamics (from nano to micro scales), a hybrid coarse-grained model is coupled with the continuum Navier-Stokes solver. Based on the Go¯-type modeling, biological dynamics is governed by the Langevin equation for which the biological macroparticles are represented by a collection of micro-sized spherical beads that are tethered by harmonic potentials. The velocity vector is coupled through the friction factors, which are amino acid dependent, in the stochastic Langevin equation. With this model, simulation results show that flow may stretch biological macroparticles to partially unravel stationary conformations that depend on the flow rate and on the terminus which is anchored. These features potentially offer richer diagnostic results to investigate biological macroparticles configuration process, as compared to force clamp results using AFM.
Analytic Solution of Gaseous Slip Heat Transfer in Micro-Channel
Authors: Zhang Tiantian , Jia Li , Wang Zhicheng , Li Yan , Li Xing
Published: June 2009

2-dimensional steady laminar fully-developed convective heat transfer between two parallel plates with constant heat flux boundary condition in slip flow region was solved analytically by using a new method based on superposition principle. Velocity slip, temperature jump at the wall and viscous heating effect were considered in the calculation. The solution method is verified for the cases where microscale effect is neglected (Kn = 0). Both the heating case and the cooling case were discussed. The effect of viscous heating on temperature and heat transfer was analyzed. The effect of Brinkman number and the Knudsen number on Nusselt number which express the heat transfer performance were analyzed systemically.
Research on Heat Transfer Characteristic of Pulsating Heat Pipe
Authors: Li Yan , Jia Li , Zhang Tiantian
Published: June 2009

In order to understand the mechanism and characteristics of the running and heat transfer of pulsating heat pipe, visualizing experimental system was established. Bottom heat mode and top heat mode have been done. In the case of bottom heat mode different diameters have been investigated. The results indicate that the total thermal resistance of PHP was decreased with heat transfer rate and increased with filling ratio for two heat mode. Thermal resistance of PHP for bottom heat mode is higher than top heat mode. The startup time is shorter for bottom heat mode than top heat mode. Thermal resistance of uneven inner diameter PHP is higher than even inner diameter pipe.
A Numerical Method for Predicting Thermoelastic Damping in Micromechanical Resonators
Authors: Xu Yang , Hao Zhili
Published: June 2009

This paper presents a numerical method for predicting thermoelastic damping (TED) in micromechanical resonators with any arbitrary structural geometry. In this numerical method, TED is interpreted as the generation of thermal energy per cycle of vibration from the viewpoint of thermal field. Consequently, TED is mathematically expressed in terms of entropy — a parameter measuring the irreversibility in heat conduction, and then numerically calculated in ANSYS/Multiphysics. The validity of this numerical method has been verified using the well-known solution to TED in a beam resonator and experimental data in the literature. Compared to the commonly used interpretation of TED in the elastic field-complex frequency, this numerical method does not involve complex values and thus offers the advantages of simplicity and compatibility with finite element modeling software.
Fabrication of Suspending GAN Microstructures With Combinations of Anisotropic and Isotropic Dry Etching Techniques
Authors: Lv Jianan , Yang Zhenchuan , Chen Kevin J.
Published: June 2009

A method for fabricating gallium nitride (GaN) based microelectromechanical (MEM) devices on silicon substrate was demonstrated. Various suspended GaN microstructures have been fabricated using ICP (Inductive coupled plasma)-based sacrificial etching of the underlying silicon with combination of both anisotropic and isotropic etching techniques, so that deeply released freestanding microstructures with minimized lateral undercut can be achieved. Cl2-based ICP-RIE (Reactive ion etching) dry etching technique is employed to pattern gallium nitride. The experimental results show that freestanding GaN microstructures with large air gap of high depth-to-width ratio can be realized by employing such two-step dry releasing technique. Fabrication results have been characterized by scanning electron microscope (SEM).
Microstructure and Strength of Low Temperature Co-Fired Ceramic Substrates With Channels and Cavities
Authors: Zhang Yang-Fei , Miao Min , Jin Yu-Feng , Bai Shu-Lin
Published: June 2009

The effect of embedded channels and cavities on the strength of LTCC substrates has been investigated by experiments, theoretical analysis and finite element analysis (FEA) simulation. The fracture behaviors characterized by flexural strength were measured by three-point bending tests and discussed according to the features of the microstructure, which was studied by Scanning Electron Microscope, Energy Spectrum Analysis and X-Ray Diffraction methods. The experimental results show that X and Y-axial channels have little effect on the flexural strength while Z-axial via-hole will greatly lower the strength due to the stress concentration. Two distinct components were observed: particles composed of synthetic corundum and matrix composed of corundum, silica, aluminum, and sodium calcium aluminum silicate. The FEA simulation gave similar results to the experiments and theoretical calculations and proved to be an effective method to predict possible condition of the fracture on substrates with complex internal structures.
Hydrodynamic and Thermal Boundary Layers Over a Flat Plate With Slip Flow and Constant Surface Heat Flux
Authors: Aziz Abdul
Published: June 2009

In this paper the boundary layer flow over a flat plat with slip flow and constant heat flux surface condition is studied. Because the plate surface temperature varies along the x direction, the momentum and energy equations are coupled due to the presence of the temperature gradient along the plate surface. This coupling, which is due to the presence of the thermal jump term in Maxwell slip condition, renders the momentum and energy equations non similar. As a preliminary study, this paper ignores this coupling due to thermal jump condition so that the self-similar nature of the equations is preserved. Even this simplified problem for the case of a constant heat flux boundary condition has remained unexplored in the literature and was therefore chosen for study in this paper. For the hydrodynamic boundary layer, velocity and shear stress distributions are presented for a range of values of the parameter characterizing the slip flow. This slip parameter is a function of the local Reynolds number, the local Knudsen number, and the tangential momentum accommodation coefficient representing the fraction of the molecules reflected diffusively at the surface. As the slip parameter increases, the slip velocity increases and the wall shear stress decreases. These results confirm the conclusions reached in other recent studies. The energy equation is solved to determine the temperature distribution in the thermal boundary layer for a range of values for both the slip parameter as well as the fluid Prandtl number. The increase in Prandtl number and/or the slip parameter reduces the dimensionless surface temperature. The actual surface temperature at any location of x is a function of the local Knudsen number, the local Reynolds number, the momentum accommodation coefficient, Prandtl number, other flow properties, and the applied heat flux.
Simulating Selective Particle Seperation in a Dielectrophoretic Microchannel
Authors: Kumar G. Naga Siva , Mitra Sushanta K.
Published: June 2009

Movement of particles in a non-uniform electric field has significant advantages. So, usage of this phenomenon has been increased in the areas of biomedical, drug delivery and point of care analysis applications for manipulating, separating, trapping, sorting of bioparticles such as cells, bacteria, viruses, proteins, DNA etc., This paper mainly deals with separating selective particles from different particles in a non-uniform electric field applied micro channels using CFD ACE+ simulations without intensive experimental trials. Simulations have been performed on parallel types of electrode arrays. Behavior of particles (vertical and translational movements) in suspending medium was identified at different frequencies, phases and voltages. Based on these results we have simulated separating the spherical microbeads of 10 micrometer from set of different sized microbeads by switching the frequencies and phases of electrodes. And also we have proposed this method for cardiac marker of myoglobin in which separating the myoglobin from blood serum and detecting it.
The Application of UV-LEDs to Microlithography
Authors: Huang Chen-Kang , Sung Jeng-Gang
Published: June 2009

Benefited by the progress of material science, Light-Emitting Diodes (LED) with UV-emitting have been produced successfully. Like other LEDs, UV-LEDs exhibit several advantages, such as energy conservation, long life, compact, and quick response. The UV-LED application to microlithography is attractive. In contrast to point light sources requiring lens to generate parallel light beams, an array of UV-LEDs can emit nearly parallel light beams easily. UV-LEDs only need 3 to 4 voltages to ignite, which is much lower than that required by mercury short arc lamps. The cost of using UV-LEDs is also much lower than current solutions. In this study, we used UV-LEDs as the light source in the laboratory lithography system. LEDs, whose emitting spectrum distributed between 370 to 410 nm mostly, were displaced on the bottom of a heat sink. Two 10-by-10 cm2 test masks, where the smallest pattern was 20 μm, were used to examine the resolution ability of this combination. Each light module was utilized to exposure photosensitized printed circuit board (PCB). After etching, the printed patterns were observed under microscope. The minimum reproducible feature size was 100 μm. Through the 4” mask, the uniformity was decent, and could be improved by using LEDs from the same batch, collimator, or LED displacement optimization. In the future, standard g-line process can be performed, and further tests will be performed to check the limits of the UV-LED system. Based on these preliminary tests, it seems like the usage of UV-LEDs should be a feasible solution for microlithography.
Design of an Organic Pixel Addressing Circuit for Active-Matrix OLED Displays
Authors: Purahmad Mohsen , Gatabi Iman Rezenejad
Published: June 2009

In this paper, we present a new model for an organic pixel addressing circuit based on four-transistor configuration. The proposed circuit doesn’t have the problems of regular configurations which are based on four-thin film transistors (TFT). Circuits based on four-TFT have many advantages, but the only problem is the existence of current peaks at the beginning of each pixel luminescence. Both 4-TFT based configuration and proposed one were simulated using HSPICE. Simulation results indicate the superiority of the proposed method compared with existing technique.
The Model of Non-Fourier Heat Conduction in a Kind of Two-Phase Medium With Great Different Heat Conductivity
Authors: Lu Wen-Qiang , Lu Junfeng
Published: June 2009

The model of non-Fourier heat conduction in a kind of two-phase mediums with great different heat conductivity is deduced by the idea and mathematics of dual phase lag. It is pointed out that the relaxation times to establish heat flux and temperature gradient include both kinds in this model: the relaxation time appeared under the conditions of applied high heat flux and rapid heating, the relaxation time introduced by the non-equilibrium heat exchange between the two-phase mediums. It is very important to distinguish the both kinds of relaxation times for analyzing and explaining the experimental phenomena of non-Fourier heat conduction in this kind of two-phase mediums.
Study of Low-Temperature Wafer Bonding With Au-Au Bonding Technique
Authors: Kurotaki H. , Shinohara H. , Kobayashi H. , Mizuno J. , Shoji S.
Published: June 2009

In general, metal diffusion bonding is carried out at a temperature in the range of 300 ∼ 400 °C and is well documented [1]. However, the knowledge of metal bonding at low temperatures below 300 °C is inadequate yet. On the other hand, low temperature metal bonding is of importance in realizing advanced integrated devices such as MEMS-Semiconductors and high-brightness LED. This paper reports the results of a feasibility study of low-temperature metal bonding with the use of Au-Au diffusion bonding technique.
Numerical Simulation of AC Electrothermal Microfluidic Pumping
Authors: Du E. , Manoochehri Souran P.
Published: June 2009

AC electrokinetic forces, such as AC electroosmosis (AC EO), AC electrothermal (AC ET) and dielectrophoresis (DEP) have been intensively investigated in manipulation of microfluids and micro/nanoparticles. AC EO effects are prone to manipulate relatively dilute electrolytes while AC ET effects extend the manipulation into conductive fluid domain. In the case of pumping high conductivity fluid, electric traveling wave signals on interdigitated electrode arrays and single-phase AC signals on asymmetric electrode structures are the two reported methods for AC ET based fluidic manipulation. This paper presents numerical simulation of the AC electric field induced electrothermal fluidic motion and pumping capacity of high conductivity fluids with stepped asymmetric electrode arrays. We investigated the effects of electrode profile and layout on pumping action and temperature rise distribution. Forward pumping mode and backward pumping mode are identified theoretically and numerically. Compared with the planar asymmetric electrode arrays, utilization of steps on electrode profile can result in significant improvement on the pumping capacity.
Self-Assembled Nanostructures
Authors: Lu Wei
Published: June 2009

A binary monolayer on an elastic substrate may self-organize into ordered nanoscale phase patterns. Here we report a work of using a substrate strain field to guide the self-assembly process. The study shows that straining a substrate uniformly does not influence the pattern. However, a non-uniform strain field significantly influences the size, shape and distribution of self-assembled features. The study suggests a method of strain field design to make various monolayer patterns.
Fabrication of Inner Micro-Grooved Pipes
Authors: Chi Y. , Du R.
Published: June 2009

Heat pipes have been applied popularly in microelectronic cooling, in which grooved heat pipes are the one of main types. Most of commercial grooved heat pipes with OD 6mm have 55 grooves and the groove width is larger than 200μm, which causes the biggest drawback of grooved heat pipes having no fine anti-gravity performance. In this paper, a fabrication method of inner micro-grooved pipes is investigated. First, a die with micro-tooth was fabricated by micro wire electrical discharge machining (WEDM). Utilizing micro wire with diameter in 30μm, it can machine micro slot with minimum size of 45μm wide, the surface roughness (Ra) is smaller than 0.1μm. Then, the die forms the micro grooves on the inner wall of pipes by high-speed spinning process. Last, the grooved pipes were draw to reduce the pipe diameter further, and then smaller grooves can be formed. The experiment results show that the width of obtained grooves is less than 100μm and the depth is about 250μm. The depth-to-width ratio increases significantly. The capillary force improves by double times, so the anti-gravity performance is better.
Molecular Dynamics Modeling of Thermal Transport in Damaged Continua
Authors: Kumar Navin , Pochiraju Kishore
Published: June 2009

The interaction between the damage state and the thermal conductivity is studied in this paper. The damage propagation and the effective thermal conductivity of the damaged continuum is studied using equilibrium molecular dynamics (EMD) method based on the Green-Kubo relation. A solid gold lattice is considered and the damage is initiated and propagated by stretching two opposite ends while system is maintained at constant volume, constant temperature (NVT) condition. Both Lennard-Jones (LJ) 6–12 and embedded-atom method (EAM) potentials are used to model the inter-atomic interactions. Results are presented illustrating the load-displacement relationship during damage growth and the thermal conductivity change behavior for a selected crack length.
Fabrication of Al Micro-Coil and Loop by Utilizing Electromigration
Authors: Sun Yuxin , Saka Masumi
Published: June 2009

Aluminum micro-coil and micro-loop have been fabricated by utilizing electromigration. In a passivated Al line with a slit at the anode end, atoms accumulated before the slit due to high current density and high substrate temperature are released from the pre-introduced holes in the passivation layer, and form micro-fibers owing to crystallization. The fibers are rotated under the existence of the transverse force induced by the tilted holes during their growth, and the micro-coil and micro-loop are fabricated.
Correcting Front-End RF Impedance Mismatch for 2.4GHz Wireless Long-Distance Data Transmission
Authors: Wang Mu-Chun , Hsieh Zhen-Ying , Chao Shu-Han , Tu Chia-Hao , Chen Shuang-Yuan
Published: June 2009

In order to increase the higher competition in low-power wireless network communication market, a high-performance and low-cost product is necessary to distinguish the difference with others. Through integrating the system performance with suitable L-shape impedance-match circuit assisting with some network analyzer, this target with a 2.4 GHz radio-frequency (RF) product in long-distance data transportation seems to be promisingly implemented. In short-distance data transportation, the ideal output-link transportation rate (∼ max. 54 Mb/sec) is slightly influenced by impedance mismatch between power amplifier (PA) and antenna port. However, it is tremendously reduced at long-distance condition and the transportation rate is decreased to ∼ 24 Mb/sec. Using the attenuator to attenuate the real input signal to –70dB to simulate the real signal transportation, the packet error rate (PER) is less than 10% at a physical sublayer service data unit (PSDU) length of 1000 bytes under the communication 802.11g spec. as the real transmission rate is 20 Mb/sec. If the impedance of the transmission line is shifted, the long-distance transportation rate will be reduced to, almost, 20 × 24 / 54 = 8.8 Mb/sec. The transportation performance is greatly deducted. With the delicate design and the feasible component arrangement, the impedance mismatch influencing the long-distance (∼ 100 m) data transportation is overcome and reduced to the acceptable range. In this investigation using 3.3 V power supply, we observe that the selection of electronic components with miniaturization is also an art to reduce the radiation side-effect.
Thermally Actuated Droplet Motion on Chemically Homogeneous, Striated, and Defected Surfaces
Authors: Chen Jian-Zhang
Published: June 2009

Experiments have demonstrated thermocapillary actuation on uniformly grafted partial-wettable surfaces. Droplet mobilization only occurs above a threshold thermal gradient or threshold droplet radius [1]. We characterized the motion instead in terms of a threshold depinning force, which successfully describes all the liquids tested. Above the depinning transition, the droplet speed, which is controlled by thermocapillary, capillary and viscous forces, increases monotonically with this reduced force parameterization. These results agree well to numerical predictions of a generalized Ford and Nadim model by using two fitting parameters, the slip coefficient and the magnitude of contact angle hysteresis [2–3]. In this follow-up study, we developed a doubly grafted surface, on which alkyltrichlorosilane coated stripes are surrounded by a more hydrophobic coating, perfluoroctyl-trichlorosilane. The quality of alkyltrichlorosilane coated stripes was still good for the thermocapillary droplet actuation, in which droplets were driven on the alkyltrichlorosilane surface and confined by the perfluoroctyl-trichlorosilane. The experimental results are also well described by a derived approximate three-dimensional model equation, which resembles the parameterization. The droplets are driven by thermocapillary force and retarded by contact angle hysteretic force, represented as contact angle hysteresis. This contact angle hysteresis is caused by chemical heterogeneity, surface roughness etc [4]. In the last part of this presentation, we will also present the thermocapillary droplet motion on a designed defected surface, which shows a tiny defect can severely hinge the droplet.
Leakage Current Influence on Microdevice Performance and Reliability
Authors: Lahav Oren , Yomtovian Its’hak , Kogut Lior
Published: June 2009

Leakage currents in microdevices have a significant impact on their performance and reliability. In the case of a microgyro, leakage currents can cause erroneous measurements, strong dependency on environmental conditions, electrical coupling, performance degradation over time (drift), and even cause failure. The influence of leakage currents on microgyro performance and reliability has been studied in this paper.
Effect of Electrical Coupling on Microgyro Performance
Authors: Yomtovian Its’hak , Lahav Oren , Ben-Itzhak Segev , Kogut Lior
Published: June 2009

Electrical coupling in microgyro is an important phenomenon which can affect its performance and reliability. The objective of this study was to characterize the influence of leakage voltages on microgyro performance. The study was performed with a vibrating microgyro, which is based on electrostatic actuation and optical sensing, and fabricated by bulk micromachining of SOI wafers. Two parameters were measured in this study: (1) amplitude ratio between leakage voltage measured on the sense pads and actuation voltage applied to the actuation pads and (2) phase shift of those voltages. It is found that the net electrostatic force exerted on the sense masses of the microgyro is quite small due to symmetry of the leakage voltages. Hence, the corresponding displacement is negligible small. Frequency dependency of the leakage voltages and resulting electrical coupling is considered as one of the mechanisms for bias short term instability and estimated to be less than 1°/hr.
Temperature and Active Layer Thickness Dependent Stability of On-Plastic a-Si:H Thin Film Transistors Fabricated at 150°C
Authors: Chen Jian-Zhang , Cheng I-Chun
Published: June 2009

Stability is an important issue for the application of TFTs. In this paper, we present the effects temperature, and humidity on the stability of inverted-staggered back-channel-cut a-Si:H TFTs of various active layer thicknesses. The amorphous TFTs were made at a process temperature of 150°C on 51-μm thick Kapton polyimide foil substrates. With active layer thickness of 50nm, humidity reversibly varies the characteristics of TFTs, but TFTs of active layer thickness greater than 100 nm is pretty stable to the humidity change, which is attributed to backchannel conduction. The temperature dependent stability and characteristics of 200nm active-layer thickness TFTs were analyzed from 20°C to 60°C. Rising temperature from 20°C to 60°C, the threshold voltage (Vt) drops about 2 volts; on-off current ratio decreases by one order of magnitude mainly due to thermally excited carriers [1].
Evaluation and Characterization of Titanium to Glass Anodic Bonding
Authors: Shu Qiong , Su Juan , Zhao Gang , Wang Ying , Chen Jing
Published: June 2009

In this paper, Ti-Glass anodic bonding is investigated on both chip and wafer level. In concern of coefficients of thermal expansion (CTE) match, three different types of ion-containing glasses are evaluated: Pyrex 7740, D-263T and soda lime glass. By applying a potential between the two chips and heating them beyond 350°C, soda lime glass samples are successfully bonded with titanium. The influence of the bonding temperature on the bonding strength is revealed. For the first time, wafer level Ti-Glass bond is carried out, a 157-μm-thick titanium wafer is successfully bonded to a 1000-μm-thick soda glass wafer at 450°C and applying a voltage of 800V and a force of 1000N for 30min, over 60% of the surface are joined. The results are helpful to define potential applications in certain field of microsystems.
Deep Trench Refilling With Parylene C for High-Quality Isolation in Bulk Micromachined Devices
Authors: Lei Yinhua , Wang Wei , Yu Huaiqiang , Li Ting , Jin Yufeng , Zhang Haixia , Li Zhihong
Published: June 2009

Isolation is usually a key factor that requires serious considerations in developing an integrated MEMS device. Here a deep trench refilling technology with parylene C was proposed to get high-quality isolation performance in bulk micro-machined devices. A 7μm wide and 50μm deep trench was etched on silicon and then refilled with parylene C to work as the functional component. A multi-step etching-refilling process was tested to improve the refilling performance. Based on primary experimental results, the trench was nearly filled by parylene C with a keyhole width less than 1.0μm. Combined with a backside slicing/etching process, the suspended trench exhibited an excellent mechanical connection performance with a breaking strength larger than 200 kPa. The present parylene C refilling technique could be a promising choice for both electrical and thermal isolation in bulk micromachined silicon devices.
3D Polymeric Devices Driven by Surface Micro Fluidic Capillaries
Authors: Xia Chunguang , Lee Howon , Fang Nicholas X.
Published: June 2009

A unique method of controlling polymer swelling locally is proposed in this work. This method relies on the novel 3D micro fabrication technology, Projection Micro strereolithography (PuSL) [1], to create capillary network in polymeric structures. The capillary network not only transports the liquid (water or organic solvents) to specific locations by capillary force when swelling is needed, but also depletes the solvent in the structure by evaporation to stop swelling. As a demonstration, functional cantilever of Poly (ethylene glycol) (PEG) driven by surface capillary is designed and tested. Integration of these functional capillary provides the way of 3D polymeric actuation.
Characterizing Metallization Introduced Polysilicon Corrosion of Surface Micromachined Structures With Submicron Capacitive Gap
Authors: Wang Yunda , Cai Ming , Wang Ying , Chen Jing
Published: June 2009

Corrosion of polysilicon occurs during the HF release, which may change the surface morphology, film thickness and even its mechanical strength; furthermore, long time exposure to HF and the presence of Au metallization appear to promote this corrosion. In this paper, clamp-clamp beams with a capacitive gap of 100nm have been manufactured to characterize this unusual phenomenon. Changes of the surface morphology are revealed, and the influence on electrical performance of the structure is evaluated. By changing the concentration of the HF, different releasing time thresholds are obtained. Although the origin of this effect is still under investigation, a simplified explanation based on the galvanic is presented. Finally, a novel method is developed to reduce the polysilicon corrosion. A parylene layer is deposited and patterned on top of the metal electrode, which proved to be very effective for isolating the Al layer.
Development of a Thermal Switch for the Heat Regulation Based on the Liquid Column Control
Authors: Jeong SuHeon , Nakayama W. , Joo JaeYoung , Lee SunKyu
Published: June 2009

The thermal switch is limited at the temperature range and the local heat transfer control due to their structures. This paper presents the development of a thermal switch for heat regulation based on the liquid column control using channel geometry effect. The most dominant factor of liquid column control is the contact angle of liquid. Therefore, the geometry of each channel was designed to affect contact angle of working fluid. Experiments were performed on a switch for the switching operation and the thermal resistance. The result shows the liquid column thermal switch can be used at the room temperature. And the heat transfer can be controlled by on/off state of the thermal switch channels.
Development and Testing of a Miniature Silicon Microgyroscope Prototype
Authors: Xia Dunzhu , Zhou Bailing , Wang Shourong
Published: June 2009

A silicon microgyroscope with the structure of area-changing capacitor detection is adopted in this paper, and the quality factor of Silicon Microgyroscope sealed with CAN mental package working under the air pressure of 10 Pa is above 3000, so its sense mode detection essentially attains better linear performance and high sensitivity. Single side driving and single side detection methods are applied to make both vibrating amplitude and frequency highly stable in drive mode circuit, and open loop difference detection method is utilized to achieve high precision detection in sense mode circuit. A miniature prototype scheme based on PCB technology has been realized with volume size of 40mm¡ 40mm¡ 30mm and power cost of less than 300 mW. The testing results demonstrate that the useful and quadrate signal will not interact because of their phase decoupling. Under the condition of the scale factor of 9.6 mV/°/s, the zero bias stability attains below 28 ° /h with linearity coefficient less than 500 ppm and simulated bandwidth more than 100 Hz, which has been improved two orders of magnitude better than that at atmospheric pressure. The engineering work is evolving at present.
Manufacture of High Aspect Ratio Bulk Titanium Micro-Parts by Inductively Coupled Plasma Etching
Authors: Zhao Gang , Shu Qiong , Li Yue , Chen Jing
Published: June 2009

A novel technology is developed to fabricate high aspect ratio bulk titanium micro-parts by inductively coupled plasma (ICP) etching. An optimized etching rate of 0.9 μm/min has been achieved with an aspect ratio higher than 10:1. For the first time, SU-8 is used as titanium etching mask instead of the traditional hard mask such as TiO2 or SiO2. With an effective selectivity of 3 and a spun-on thickness beyond 100 μm, vertical etching sidewall and low sidewall roughness are obtained. Ultra-deep titanium etching up to 200 μm has been realized, which is among the best of the present reports. Titanium micro-springs and planks are successfully fabricated with this approach.
A Combined Model and Its Verification for Femtosecond-Pulse Materials Interactions
Authors: Jiang Lan , Tsai Hai-Lung
Published: June 2009

This paper reports the overall picture of our ongoing efforts to establish the scientific understanding of ultrafast, non-equilibrium laser-material interactions from nanometer to milimeter and from femtosecond to microsecond through comprehensive, integrated multiscale physico-chemical modeling and experimental verification. A novel plasma model with quantum treatments is developed to account for significantly varying optical properties. The model is used to successfully predict two uncommon phenomena that is experimentally observed: 1) a flat-bottom crater shape created by a Gaussian beam and 2) repeatable nanoscale structures achieved by pulse train technology. The well known two-temperature model is improved by considering the quantum effects of different heat carriers and then is used to accurately predict the damage thresholds for metals. Preliminary results for these ongoing modeling efforts are reported in this article.
Analysis of Electrostatically Actuated Narrow Microcantilevers Using Rayleigh-Ritz Energy Technique
Authors: Joglekar Manish M. , Hardikar Kedar Y. , Pawaskar Dnyanesh N.
Published: June 2009

The operation of electrostatically actuated MEMS devices involves an inherent phenomenon termed as the pull-in instability which reduces their useful travel range. Accurate prediction of pull-in parameters (pull-in displacement and pull-in voltage) is hence vital in the design of such microdevices. In this article, we present a complete nondimensional formulation and implementation of an efficient numerical scheme based on the Rayleigh-Ritz energy technique to determine the static pull-in parameters of an electrostatically actuated narrow microcantilever beam. Deflection of the beam is approximated by an admissible polynomial function that satisfies its mechanical boundary conditions. The principle of stationary potential energy and the condition of instability are then applied to obtain a highly nonlinear algebraic equation which is solved using the Fibonacci minimization algorithm. An optimum number of Gauss quadrature points is used to integrate the nonlinear electrostatic terms. Two mathematical models accounting for the fringing field capacitance are examined in turn. A comparison is made between the normalized values of pull-in parameters obtained by considering the two aforementioned fringing field models. Two examples of electrostatically actuated narrow microcantilevers are then solved using the proposed scheme for the validation purpose. For these examples, a comparison is made between the values of pull-in parameters obtained using the proposed scheme and those previously published in the literature. An excellent agreement between the two establishes the utility of the proposed scheme.
Design and Simulation of Piezoelectric Micro-Cantilever Ultrasonic Transducers for Audio Directional Loudspeakers
Authors: Ma Teng , Cai Chenguang , Xu Limei , Xu Leon , Wang Xia , Ma Jian , Qiu Chuankai
Published: June 2009

This paper presents a piezoelectric multilayered microcantilever structure as a micro-electro-mechanical system (MEMS) transducer. The proposed micro-transducer is designed for novel audio directional loudspeaker for mobile communication devices. To obtain optimum design parameters and predict the cantilever performance before actual fabrication, the mechanical and electro-mechanical performance was simulated by the finite element method and further validated with theoretical calculation. Finally the fabrication process steps are proposed.
Fabrication of SiC MEMS Pressure Sensor Based on Novel Vacuum-Sealed Method
Authors: Wang Chao , Geng Xiaobao , Zhang Haixia
Published: June 2009

Fabrication of SiC MEMS pressure sensor based on novel vacuum-sealed method is presented in this paper. The sensor was fabricated using surface micromachining. Due to its excellent mechanical properties and high chemical resistance, PECVD (Plasma Enhanced Chemical Vapor Deposition) SiC was chosen as structural material. Polyimide acts as sacrificial layer which solve stiction problem in process. STS PECVD system is utilized to realize releasing, deposition and vacuum sealing consecutively in the process chamber, by this method wafer cleaning step was avoided before releasing the sacrificial layer, therefore, stiction problem is prevented. This fabrication technology can achieve high yield and low cost.
Fabrication of SiC MEMS Pressure Sensor by Anodic Bonding
Authors: Tang Wei , Chen Zhe , Tian Dayu , Zhang Haixia
Published: June 2009

Due to its outstanding chemical stability and mechanical properties, silicon carbide (SiC) is one of the best materials for harsh environment applications. In this work, bulk micromachining technique was utilized to fabricate a PECVD SiC pressure sensor. This technique simplified the process and solved the stickiness problem in surface micromachining. The whole fabrication temperature is under 450°C, which makes it compatible with the CMOS process.
PFPE Modified Silicon Nano-Textured Surfaces for Adhesion and Friction Reduction
Authors: Song Ying , Wang Hengyu , Zou Min
Published: June 2009

This paper reports a new technique of producing hydrophobic surfaces with WCA as high as 147°. This technique consists of first generating nano-textures on a silicon surface via aluminum-induced crystallization (AIC) of amorphous silicon (a-Si) and then applying perfluoropolyether (PFPE) on the nano-textured surface (NTS). The resulting PFPE-modified NTS showed significant improvement on both surface hydrophobicity and tribological performances compared to a PFPE-modified smooth silicon surface.
Nanoindentation on a Ni Nanodot-Patterned Surface
Authors: Wang Hengyu , Zou Min , Jackson Robert L. , Larson Preston R. , Johnson Matthew B.
Published: June 2009

Nanoindentation on a Ni nanodot-patterned surface (NDPS) was investigated experimentally and numerically. The Ni NDPS consists of well-ordered arrays of Ni nanodots with approximately the same size and shape. The nanoindentation experiments were performed on the Ni NDPS using diamond tips of 1 and 5 μm radii of curvature. To efficiently simulate large number of nanodots in contact, numerical simulations were carried out using formulae empirically fitted from a finite element (FE) study of a single spherical contact. The simulation results were found to be in good agreement with the experimental results.
Nanoindentation Characterization of Ultrafine-Grained Surface Layer by Turning Versus Grinding
Authors: Warren A. W. , Guo Y. B.
Published: June 2009

Hard turning and grinding are competing precision machining processes for the manufacture of mechanical components such as bearings, gears, cams, etc. Surface hardening at gentle machining conditions has often been reported and is attributed to ultrafine-grained and size effect. However, there are controversial results about surface hardness. Due to the great importance of surface property to component performance such as fatigue and wear, it is imperative to clarify surface hardening mechanisms. The purpose of this paper is to investigate surface hardening and mechanism. Hard turning and grinding of AISI 52100 steel was conducted using gentle machining conditions. Surface integrity was then analyzed in terms of surface microstructure, microhardness, and nanohardness. The research findings showed that the apparent softening measured using microindentation in near surface is not due to thermal effects, but rather a misinterpretation of hardness values due to improper testing technique. Hard turning induces a thicker plastically deformed ultrafine-grained (50∼100 nm) layer than grinding. However, the grinding induced grain size may be smaller that by turning, which produces higher hardness on the ground surface.
The Influence of Residual Stress and Tip Geometry on the Measurement of Surface Property Using Nanoindentation: Experimental Study and Numerical Analysis
Authors: Warren A. W. , Guo Y. B.
Published: June 2009

This study focuses on the basic relationships between nanohardness, residual stress, and micro/nanostructure of precision machined surfaces of high carbon steels. A series of nanoindentation tests were conducted on the cross-sections of the precision machined surfaces with ultrafine-grains or nanostructures. It was found that the nanostructured white layer significantly increases nanohardness, while the ultrafine-grained layer only slightly increases surface hardness. Residual stress affects the load-displacement curve shape at the onset of material yielding. Nanostructure makes a significant difference on the characteristics of a load-displacement curve, while ultrafine-grained structure exerts a slight influence. The influence of residual stress on the load-displacement curve can be estimated by finite element simulation of a nanoindentation. The simulation sensitivity analysis shows that the load-displacement curves are significantly affected by residual stress.
Design of a Valveless Micropump for Medical Drug Delivery Systems
Authors: Leung W. W. F. , Cheng C. H. , Lei K. F. , Chao C. , Cheung T. H. , Yueng P. K. , Yuen P. T.
Published: June 2009

The objective is to develop improved microvalve and micropump designs to simplify fabrication process, decrease manufacturing cost and increase efficiency. In this paper, a new prototype model of a micropump using piezoelectric (PZT) disc as the actuator is designed. This paper describes the structure and the working principle of new micropump using PZT disc as an actuator. The main basic structure includes a pump body with valveless structure and piezoelectric disc. The overall size of this prototype is the same as the diameter of a PZT disc about 4cm × 5cm. The working principle relies on the vibration of a membrane by applying a.c. voltage to the PZT actuator. The fabrication process is simplified, comparing with traditional manufacturing method and save time and cost. While fabrication and design are discussed herein, experimental results and pump performance will be reported separately. The developed micropump is able to produce a micro-flow rate suitable for medical applications such as drug delivery system.