Nickel nanowires with large aspect ratio of up to 300 have been prepared by a hydrazine hydrate reduction method under applied magnetic field. The diameter of nickel nanowires is about 200 nm and length up to 60 μm. ...Nickel nanowires with large aspect ratio of up to 300 have been prepared by a hydrazine hydrate reduction method under applied magnetic field. The diameter of nickel nanowires is about 200 nm and length up to 60 μm. The role of magnetic field on the growth of magnetic nanowires is discussed and a magnetic nanowire growth mechanism has been proposed. Nickel ions are firstly reduced to nickel atoms by hydrazine hydrates in a strong alkaline solution and grow into tiny spherical nanoparticles. Then, these magnetic particles will align under a magnetic force and form linear chains. Furthermore, the as-formed chains can enhance the local magnetic field and attract other magnetic particles nearby, resulting finally as linear nanowires. The formation and the size of nanowires depend strongly on the magnitude of applied magnetic field.展开更多
Fe3O4 ferrofluids containing monodisperse Fe3O4 nanoparticles with different diameters of 8, 12, 16 and 18nm are prepared by using high-temperature solution phase reaction. The particles have single crystal structures...Fe3O4 ferrofluids containing monodisperse Fe3O4 nanoparticles with different diameters of 8, 12, 16 and 18nm are prepared by using high-temperature solution phase reaction. The particles have single crystal structures with narrow size distributions. At room temperature, the 8-nm ferrofluid shows superparamagnetic behaviour, whereas the others display hysteresis properties and the coercivity increases with the increasing particle size. The spin glass-like behaviour and cusps near 190K are observed on all ferrofluids according to the temperature variation of field-cooled （FC） and zero-field-cooled （ZFC） magnetization measurements. The cusps are found to be associated with the freezing point of the solvent. As a comparison, the ferrofluids are dried and the FC and ZFC magnetization curves of powdery samples are also investigated. It is found that the blocking temperatures for the powdery samples are higher than those for their corresponding ferrofluids. Moreover, the size dependent heating effect of the ferrofluids is also investigated in ac magnetic field with a frequency of 55 kHz and amplitude of 200 Oe.展开更多
Highly conductive boron-doped hydrogenated mieroerystalline silicon （μc-Si：H） films are prepared by very high frequency plasma enhanced chemical vapour deposition （VHF PECVD） at the substrate temperatures （Ts）...Highly conductive boron-doped hydrogenated mieroerystalline silicon （μc-Si：H） films are prepared by very high frequency plasma enhanced chemical vapour deposition （VHF PECVD） at the substrate temperatures （Ts） ranging from 90℃ to 270℃. The effects of Ts on the growth and properties of the films are investigated. Results indicate that the growth rate, the electrical （dark conductivity, carrier concentration and Hall mobility） and structural （crystallinity and grain size） properties are all strongly dependent on Ts. As Ts increases, it is observed that 1） the growth rate initially increases and then arrives at a maximum value of 13.3 nm/min at Ts=210℃, 2） the crystalline volume fraction （Xc） and the grain size increase initially, then reach their maximum values at TS=140℃, and finally decrease, 3） the dark conductivity （σd）, carrier concentration and Hall mobility have a similar dependence on Ts and arrive at their maximum values at Ts-190℃. In addition, it is also observed that at a lower substrate temperature Ts, a higher dopant concentration is required in order to obtain a maximum σd.展开更多
TiO2 thin films were deposited on glass substrates by sputtering in a conventional rf magnetron sputtering system. X-ray diffraction pattern and transmission spectrum were measured. The curves of refraction index and ...TiO2 thin films were deposited on glass substrates by sputtering in a conventional rf magnetron sputtering system. X-ray diffraction pattern and transmission spectrum were measured. The curves of refraction index and extinction coefficient distributions as well as the thickness of films calculated from transmission spectrum were obtained. The optimization problem was also solved using a method based on a constrained nonlinear programming algorithm.展开更多
Microstructure and phase transformation behaviors of the film annealed at different temperatures were studied by X-ray diffractometry （XRD）, transmission electron microscopy and differential scanning calorimeter （...Microstructure and phase transformation behaviors of the film annealed at different temperatures were studied by X-ray diffractometry （XRD）, transmission electron microscopy and differential scanning calorimeter （DSC）. Also tensile tests were examined. For increasing annealed temperature, multiple phase transformations, transformations via a B19-phase or direct martensite/austenite transformtion are observed. The TiNiPd thin film annealed at 750℃ had relatively uniform martensite/austenite transformtion and shape memory effect. Martensite/austenite transformtion was also found in strain-temperature curves. Subsequent annealing at 450℃ had minor effect on transformation temperatures of Ti-Ni-Pd thin films but resulted in more uniform transformation and improved shape memory effect.展开更多
Si-doped Ge2Sb2Te5 films have been prepared by dc magnetron co-sputtering with Ge2Sb2Te5 and Si targets. The addition of Si in the Ge2Sb2Te5 film results in the increase of both crystallization temperature and phasetr...Si-doped Ge2Sb2Te5 films have been prepared by dc magnetron co-sputtering with Ge2Sb2Te5 and Si targets. The addition of Si in the Ge2Sb2Te5 film results in the increase of both crystallization temperature and phasetransition temperature from face-centred-cubic （fcc） phase to hexagonal （hex） phase. The resistivity of the Ge2Sb2Te5 film shows a significant increase with the Si doping. When doping 11.8 at.% of Si in the film, the resistivity after 460℃ annealing increases from 1 to 11 mΩ.cm and dynamic resistance increase from 64 to 99Ω compared to the undoped Ge2Sb2Te5 film. This is very helpful to writing current reduction of phase-change random access memory.展开更多
One-dimensional Ni nanostructures were synthesized via a hydrazine reduction route under external magnetic fields. The mixture of de-ionized water and ethanol was used as the reaction solvent and hydrazine hydrate as ...One-dimensional Ni nanostructures were synthesized via a hydrazine reduction route under external magnetic fields. The mixture of de-ionized water and ethanol was used as the reaction solvent and hydrazine hydrate as reducing agents. The morphology and properties of Ni nanostructures were characterized by X-ray diffractometer(XRD), scanning electron microscopy(SEM), and vibrating sample magnetometer(VSM). It was found that the magnetic field strength, concentration of Ni ions,reaction time and temperature as well as p H values played key roles on formation, microstructures and magnetic properties of Ni nanowires. The optimal wires have diameter of ~200 nm and length up to ~200 μm. And their coercivity is ~260 Oe, which is much larger than the commercial Ni powders of 31 Oe. This work presents a simple, low-cost, environment-friendly and large-scale production approach to fabricate one-dimensional magnetic materials. The resulting materials may have potential applications in conductive filters, magnetic sensors and catalytic agents.展开更多
The virtual machine of code mechanism （VMCM） as a new concept for code mechanical solidification and verification is proposed and can be applied in MEMS （micro-electromechanical systems） security device for high c...The virtual machine of code mechanism （VMCM） as a new concept for code mechanical solidification and verification is proposed and can be applied in MEMS （micro-electromechanical systems） security device for high consequence systems. Based on a study of the running condition of physical code mechanism, VMCM＇s configuration, ternary encoding method, running action and logic are derived. The cases of multi-level code mechanism are designed and verified with the VMCM method, showing that the presented method is effective.展开更多
A micromachined electrostatically suspended gyroscope(MESG)based on UV-LIGA microfabrication process was introduced.By close-loop control,the suspended rotor is kept in null position and through the torque rebalance l...A micromachined electrostatically suspended gyroscope(MESG)based on UV-LIGA microfabrication process was introduced.By close-loop control,the suspended rotor is kept in null position and through the torque rebalance loop,in which the output control voltages reflects the input angular velocity,a dual-axis input angular velocity can be measured simultaneously.First,the system model of MESG was established by dynamic analysis based on the torque analysis.Then,the rebalance loop under ideal condition is designed using modern control technique.The performance of the designed decoupling rebalance loop was compared with that of conventional proportional integral differential(PID)rebalance loop combined with the compensation loop.In order to realize the decoupling of the output voltages,a compensated decoupling matrix and its difference equation were presented and realized by a digital decoupling method employing digital signal processor(DSP).It was confirmed that the controller could realize the complete decoupling and improve the performance of the gyroscope,which includes merits of fast response speed,low overshoot and good dynamic performance,as the simulation results shown.At last,the circuit and digital realization scheme were given.展开更多
A differential capacitance detection circuit aiming at detection of rotating angle in a novel levitation structure is presented. To ensure the low non-linearity and high resolution, noise analysis and non-linearity si...A differential capacitance detection circuit aiming at detection of rotating angle in a novel levitation structure is presented. To ensure the low non-linearity and high resolution, noise analysis and non-linearity simulation are conducted. In the capacitance interface, an integral charge amplifier is adopted as a front end amplifier to reduce the parasitic capacitance caused by connecting wire. For the novel differential capacitance bridge with a coupling capacitor, the noise floor and non-linearity of the detection circuit are analyzed, and the results show that the detecting circuit is capable of realizing angle detection with high angular resolution and relative low non-linearity. With a specially designed printed circuit board, the circuit is simulated by PSpice. The practical experiment shows that the detection board can achieve angular resolution as high as 0.04° with a non-linearity error 2.3%.展开更多
Hydrogenated microcrystalline and amorphous silicon thin films were prepared by very high frequency plasmaenhanced chemical vapour deposition （VHF PECVD） by using a mixture of silane and hydrogen as source gas. The ...Hydrogenated microcrystalline and amorphous silicon thin films were prepared by very high frequency plasmaenhanced chemical vapour deposition （VHF PECVD） by using a mixture of silane and hydrogen as source gas. The influence of deposition parameters on the transition region of hydrogenated silicon films growth was investigated by varying the silane concentration （SC）, plasma power （Pw）, working pressure （P）, and substrate temperature （Ts）. Results suggest that SC and Ts are the most critical factors that affect the film structure transition from microcrystalline to amorphous phase. A narrow region in the range of SC and Ts, in which the rapid phase transition takes place, was identified. It was found that at lower P or higher Pw, the transition region is shifted to larger SC. In addition, the dark conductivity and photoconductivity decrease with SC and show sharp changes in the transition region. It proposed that the transition process and the transition region are determined by the competition between the etching effect of atomic hydrogen and the growth of amorphous phase.展开更多
The 3D model of flapping wing mechanism and veins is constructed in 3D computer aided design (CAD) software UG.Then the co-simulation model is established by using multibody dynamics software ADAMS and MATLAB.The vali...The 3D model of flapping wing mechanism and veins is constructed in 3D computer aided design (CAD) software UG.Then the co-simulation model is established by using multibody dynamics software ADAMS and MATLAB.The validation of this co-simulation model is verified by comparing the simulation results with final experiments.The simulation results and experiments reveal that the relation between flapping frequency and driving voltage of motor is approximately linear under various wingspans.The variance of flapping frequency among different wingspans augments gradually with increasing voltage.Furthermore,the simulation results suggest that flapping frequency is sensitive to wingspan and decreases with increasing wingspan of veins,and the relation between flapping frequency and moment of inertia of veins is also approximately linear for various voltages.展开更多
We have proposed a novel noncontact ultrasonic motor based on non-syinmetrical electrode driving. The configuration of this electrode and the fabrication process of rotors are presented. Its vibration characteristics ...We have proposed a novel noncontact ultrasonic motor based on non-syinmetrical electrode driving. The configuration of this electrode and the fabrication process of rotors are presented. Its vibration characteristics are computed and analysed by using the finite element method and studied experimentally. Good agreement between them is obtained. Moreover, it is also shown that this noncontact ultrasonic motor is operated in antisymmetric radial vibration mode of B21 mode. The maximum revolution speed for three-blade and six-blade rotors are 5100 and 3700r/min at an input voltage of 20V, respectively. Also, the noncontact high-speed revolution of the rotors can be realized by the parts of Ⅰ, Ⅲ of the electrode or Ⅱ, Ⅳ of the electrode. The levitation distance between the s tator and rotor is about 140μm according to the theoretical calculation and the experimental measurement.展开更多
Soft lithography is a low-cost and convenient method for the forming and manufacturing of micro/ nanostructures compared to the traditional optical lithography. In soft lithography, poly（dimethylsiloxane） （PDMS） s...Soft lithography is a low-cost and convenient method for the forming and manufacturing of micro/ nanostructures compared to the traditional optical lithography. In soft lithography, poly（dimethylsiloxane） （PDMS） stamps with relief structures have been widely used to transfer patterns. The traditional fabrication approach of PDMS stamps is time-consuming since the master has been occupied during the curing process. By adding and repeating fast nanoimprint step, many intermediate polymeric molds can be produced from the master and these molds can then be employed to replicate more PDMS stamps while the time used is close to that of the common way. We demonstrated this idea by three masters which were made by the DEM （Deepetching, Electroforming and Microreplicating） and FIB （Focused Ion Beam） techniques. The photos show that the patterns on the PMDS stamps successfully duplicated patterns on the origin masters.展开更多
A simple autonomous docking method based on infrared sensors for mobile self-reconfigurable relay microrobots is proposed in the paper.The IR guidance system composed of an IR receiver and four IR emitters is designed...A simple autonomous docking method based on infrared sensors for mobile self-reconfigurable relay microrobots is proposed in the paper.The IR guidance system composed of an IR receiver and four IR emitters is designed,analyzed and developed.The autonomous docking control method based on centering alignment and dynamic motion planning is adopted so that it has high efficiency and reliability.Two basic microrobot prototypes are developed,and related docking experiments are done to verify the feasibility of the approach.展开更多
The interaction between gold nanoparticles and proteins such as bovine serum albumin and immunoglobulin G under the condition of different pH values was studied based on the measurement of zeta potential and fluoresce...The interaction between gold nanoparticles and proteins such as bovine serum albumin and immunoglobulin G under the condition of different pH values was studied based on the measurement of zeta potential and fluorescence quenching of the proteins before and after proteins were bound with gold nanoparticles. Aggregations were found in gold colloid aqueous solution after addition of proteins by TEM characterization and UV-Vis spectroscopy deterruination. The results showed that the values of zeta potential were quite different, the binding constant Kb and stoichiometry n were slightly increased with the increase of pH value. In conclusion, two factors could affect markedly the interaction between gold nanoparticles and proteins, that is, surface charge and the coordination effect between gold nanoparticles and indole group of the tryptophan residue of proteins.展开更多
In-situ tensile testing in TEM (transmission electron microscopy) is a useful tool for studying mechanical properties of nano-structures because it can provide quanti-tative information on sample deformation at atomic...In-situ tensile testing in TEM (transmission electron microscopy) is a useful tool for studying mechanical properties of nano-structures because it can provide quanti-tative information on sample deformation at atomic scale. To facilitate in-situ TEM tensile tests of SCS (single crystal silicon) nanobeam, a MEMS tensile-testing chip was designed and fabricated. The chip was fabricated by means of bulk micro-machining and wafer bonding techniques. An SCS nanobeam, a comb drive ac-tuator, a force sensor beam and an electron beam window were integrated into the chip. With the on-chip comb-drive-actuator stretching the nanobeam and in-situ TEM observation, tensile test on a 90 nm-thick nanobeam was performed and the strain-stress relationship was obtained. The Young's modulus was fitted to be 161 GPa and did not show the size effect.展开更多
Hydrogenated silicon （Si：H） thin films for application in solar ceils were deposited by using very high frequency plasma enhanced chemical vapour deposition （VHF PECVD） at a substrate temperature of about 170 ℃,...Hydrogenated silicon （Si：H） thin films for application in solar ceils were deposited by using very high frequency plasma enhanced chemical vapour deposition （VHF PECVD） at a substrate temperature of about 170 ℃, The electrical, structural, and optical properties of the films were investigated. The deposited films were then applied as i-layers for p-i-n single junction solar cells. The current-voltage （I - V） characteristics of the cells were measured before and after the light soaking. The results suggest that the films deposited near the transition region have an optimum properties for application in solar cells. The cell with an i-layer prepared near the transition region shows the best stable performance.展开更多
Metal-oxide-semiconductor field effect transistor(MOSFET) intrinsic gain degradation caused by channel length modulation(CLM) effect is examined.A simplified model based on Berkeley short-channel insulator-gate field ...Metal-oxide-semiconductor field effect transistor(MOSFET) intrinsic gain degradation caused by channel length modulation(CLM) effect is examined.A simplified model based on Berkeley short-channel insulator-gate field effect transistor model version 4(BSIM4) current expression for sub-100 nm MOSFET intrinsic gain is deduced,which only needs a few technology parameters.With this transistor intrinsic gain model,complementary metal-oxide-semiconductor(CMOS) operational amplifier(op amp) DC gain could be predicted.A two-stage folded cascode op amp is used as an example in this work.Non-minimum length device is used to improve the op amp DC gain.An improvement of 20 dB is proved when using doubled channel length design.Optimizing transistor bias condition and using advanced technology with thinner gate dielectric thickness and shallower source/drain junction depth can also increase the op amp DC gain.After these,a full op amp DC gain scaling roadmap is proposed,from 130 nm technology node to 32 nm technology node.Five scaled op amps are built and their DC gains in simulation roll down from 69.6 to 41.1 dB.Simulation shows transistors biased at higher source-drain voltage will have more impact on the op amp DC gain scaling over technology.The prediction based on our simplified gain model agrees with SPICE simulation results.展开更多
The selection of solvents for SiC nanowires（NWs） in a dielectrophoretic process is discussed theoretically and experimentally.From the viewpoints of dielectrophoresis force and torque,volatility,as well as toxicity,...The selection of solvents for SiC nanowires（NWs） in a dielectrophoretic process is discussed theoretically and experimentally.From the viewpoints of dielectrophoresis force and torque,volatility,as well as toxicity, isopropanol（IPA） is considered as a proper candidate.By using the dielectrophoretic process,SiC NWs are aligned and NW thin films are prepared.The densities of the aligned SiC NWs are 2μm^（-1）,4μm^（-1）,6μm^（-1）,which corresponds to SiC NW concentrations of 0.1μg/μL,0.3μg/μL and 0.5μg/μL,respectively.Thin-film transistors are fabricated based on the aligned SiC NWs of 6μm^（-1）.The mobility of a typical device is estimated to be 13.4cm^2/（V·s）.展开更多
基金supported by the Hi-Tech Research and Development Program of China(No.2007AA03Z300)Shanghai-Applied Materials Research and Development fund(No.07SA10)+3 种基金National Natural Science Foundation of China(No.50730008)Shanghai Science and Technology Grant(No:0752nm015,09ZR1414800,1052nm05500)National Basic Research Program of China(No.2006CB300406)the fund of Defence Key Laboratory of Nano/Micro Fabrication Technology
文摘Nickel nanowires with large aspect ratio of up to 300 have been prepared by a hydrazine hydrate reduction method under applied magnetic field. The diameter of nickel nanowires is about 200 nm and length up to 60 μm. The role of magnetic field on the growth of magnetic nanowires is discussed and a magnetic nanowire growth mechanism has been proposed. Nickel ions are firstly reduced to nickel atoms by hydrazine hydrates in a strong alkaline solution and grow into tiny spherical nanoparticles. Then, these magnetic particles will align under a magnetic force and form linear chains. Furthermore, the as-formed chains can enhance the local magnetic field and attract other magnetic particles nearby, resulting finally as linear nanowires. The formation and the size of nanowires depend strongly on the magnitude of applied magnetic field.
文摘Fe3O4 ferrofluids containing monodisperse Fe3O4 nanoparticles with different diameters of 8, 12, 16 and 18nm are prepared by using high-temperature solution phase reaction. The particles have single crystal structures with narrow size distributions. At room temperature, the 8-nm ferrofluid shows superparamagnetic behaviour, whereas the others display hysteresis properties and the coercivity increases with the increasing particle size. The spin glass-like behaviour and cusps near 190K are observed on all ferrofluids according to the temperature variation of field-cooled （FC） and zero-field-cooled （ZFC） magnetization measurements. The cusps are found to be associated with the freezing point of the solvent. As a comparison, the ferrofluids are dried and the FC and ZFC magnetization curves of powdery samples are also investigated. It is found that the blocking temperatures for the powdery samples are higher than those for their corresponding ferrofluids. Moreover, the size dependent heating effect of the ferrofluids is also investigated in ac magnetic field with a frequency of 55 kHz and amplitude of 200 Oe.
文摘Highly conductive boron-doped hydrogenated mieroerystalline silicon （μc-Si：H） films are prepared by very high frequency plasma enhanced chemical vapour deposition （VHF PECVD） at the substrate temperatures （Ts） ranging from 90℃ to 270℃. The effects of Ts on the growth and properties of the films are investigated. Results indicate that the growth rate, the electrical （dark conductivity, carrier concentration and Hall mobility） and structural （crystallinity and grain size） properties are all strongly dependent on Ts. As Ts increases, it is observed that 1） the growth rate initially increases and then arrives at a maximum value of 13.3 nm/min at Ts=210℃, 2） the crystalline volume fraction （Xc） and the grain size increase initially, then reach their maximum values at TS=140℃, and finally decrease, 3） the dark conductivity （σd）, carrier concentration and Hall mobility have a similar dependence on Ts and arrive at their maximum values at Ts-190℃. In addition, it is also observed that at a lower substrate temperature Ts, a higher dopant concentration is required in order to obtain a maximum σd.
文摘TiO2 thin films were deposited on glass substrates by sputtering in a conventional rf magnetron sputtering system. X-ray diffraction pattern and transmission spectrum were measured. The curves of refraction index and extinction coefficient distributions as well as the thickness of films calculated from transmission spectrum were obtained. The optimization problem was also solved using a method based on a constrained nonlinear programming algorithm.
基金supported by Science&Technology Commission of Shanghai Municipality(STCSM),China(No.02DJ14042)the Key Project of Chinese Ministry of Education(No.0307).
文摘Microstructure and phase transformation behaviors of the film annealed at different temperatures were studied by X-ray diffractometry （XRD）, transmission electron microscopy and differential scanning calorimeter （DSC）. Also tensile tests were examined. For increasing annealed temperature, multiple phase transformations, transformations via a B19-phase or direct martensite/austenite transformtion are observed. The TiNiPd thin film annealed at 750℃ had relatively uniform martensite/austenite transformtion and shape memory effect. Martensite/austenite transformtion was also found in strain-temperature curves. Subsequent annealing at 450℃ had minor effect on transformation temperatures of Ti-Ni-Pd thin films but resulted in more uniform transformation and improved shape memory effect.
文摘Si-doped Ge2Sb2Te5 films have been prepared by dc magnetron co-sputtering with Ge2Sb2Te5 and Si targets. The addition of Si in the Ge2Sb2Te5 film results in the increase of both crystallization temperature and phasetransition temperature from face-centred-cubic （fcc） phase to hexagonal （hex） phase. The resistivity of the Ge2Sb2Te5 film shows a significant increase with the Si doping. When doping 11.8 at.% of Si in the film, the resistivity after 460℃ annealing increases from 1 to 11 mΩ.cm and dynamic resistance increase from 64 to 99Ω compared to the undoped Ge2Sb2Te5 film. This is very helpful to writing current reduction of phase-change random access memory.
基金support of the National Basic Research Program of China(No.2006CB300406)Shanghai Science and Technology Grant(No:0752nm015)+2 种基金National Natural Science Foundation of China(No.50730008,20504021)Natural Science Foundation of Shanghai(No.09ZR1414800)Shanghai Applied Materials Collaborative Research Program(No:09520714400)
文摘One-dimensional Ni nanostructures were synthesized via a hydrazine reduction route under external magnetic fields. The mixture of de-ionized water and ethanol was used as the reaction solvent and hydrazine hydrate as reducing agents. The morphology and properties of Ni nanostructures were characterized by X-ray diffractometer(XRD), scanning electron microscopy(SEM), and vibrating sample magnetometer(VSM). It was found that the magnetic field strength, concentration of Ni ions,reaction time and temperature as well as p H values played key roles on formation, microstructures and magnetic properties of Ni nanowires. The optimal wires have diameter of ~200 nm and length up to ~200 μm. And their coercivity is ~260 Oe, which is much larger than the commercial Ni powders of 31 Oe. This work presents a simple, low-cost, environment-friendly and large-scale production approach to fabricate one-dimensional magnetic materials. The resulting materials may have potential applications in conductive filters, magnetic sensors and catalytic agents.
基金Project supported by High-Technology Research and Develop-ment Program of China (Grant No .863 -2003AA404210)
文摘The virtual machine of code mechanism （VMCM） as a new concept for code mechanical solidification and verification is proposed and can be applied in MEMS （micro-electromechanical systems） security device for high consequence systems. Based on a study of the running condition of physical code mechanism, VMCM＇s configuration, ternary encoding method, running action and logic are derived. The cases of multi-level code mechanism are designed and verified with the VMCM method, showing that the presented method is effective.
基金Sponsored by the Pre-weapons Research Fund(Grant No.9140A09020706JW0314)New Teacher Research Fund for the Doctoral Program of HigherEducation of China(Grant No.200802481026)
文摘A micromachined electrostatically suspended gyroscope(MESG)based on UV-LIGA microfabrication process was introduced.By close-loop control,the suspended rotor is kept in null position and through the torque rebalance loop,in which the output control voltages reflects the input angular velocity,a dual-axis input angular velocity can be measured simultaneously.First,the system model of MESG was established by dynamic analysis based on the torque analysis.Then,the rebalance loop under ideal condition is designed using modern control technique.The performance of the designed decoupling rebalance loop was compared with that of conventional proportional integral differential(PID)rebalance loop combined with the compensation loop.In order to realize the decoupling of the output voltages,a compensated decoupling matrix and its difference equation were presented and realized by a digital decoupling method employing digital signal processor(DSP).It was confirmed that the controller could realize the complete decoupling and improve the performance of the gyroscope,which includes merits of fast response speed,low overshoot and good dynamic performance,as the simulation results shown.At last,the circuit and digital realization scheme were given.
基金Foundation item： National Natural Science Foundation of China （60402003） The Key National Basic Research and Development Program of China （2002AA745120）
文摘A differential capacitance detection circuit aiming at detection of rotating angle in a novel levitation structure is presented. To ensure the low non-linearity and high resolution, noise analysis and non-linearity simulation are conducted. In the capacitance interface, an integral charge amplifier is adopted as a front end amplifier to reduce the parasitic capacitance caused by connecting wire. For the novel differential capacitance bridge with a coupling capacitor, the noise floor and non-linearity of the detection circuit are analyzed, and the results show that the detecting circuit is capable of realizing angle detection with high angular resolution and relative low non-linearity. With a specially designed printed circuit board, the circuit is simulated by PSpice. The practical experiment shows that the detection board can achieve angular resolution as high as 0.04° with a non-linearity error 2.3%.
文摘Hydrogenated microcrystalline and amorphous silicon thin films were prepared by very high frequency plasmaenhanced chemical vapour deposition （VHF PECVD） by using a mixture of silane and hydrogen as source gas. The influence of deposition parameters on the transition region of hydrogenated silicon films growth was investigated by varying the silane concentration （SC）, plasma power （Pw）, working pressure （P）, and substrate temperature （Ts）. Results suggest that SC and Ts are the most critical factors that affect the film structure transition from microcrystalline to amorphous phase. A narrow region in the range of SC and Ts, in which the rapid phase transition takes place, was identified. It was found that at lower P or higher Pw, the transition region is shifted to larger SC. In addition, the dark conductivity and photoconductivity decrease with SC and show sharp changes in the transition region. It proposed that the transition process and the transition region are determined by the competition between the etching effect of atomic hydrogen and the growth of amorphous phase.
基金the National Natural Science Foundationof China(No.60375033)
文摘The 3D model of flapping wing mechanism and veins is constructed in 3D computer aided design (CAD) software UG.Then the co-simulation model is established by using multibody dynamics software ADAMS and MATLAB.The validation of this co-simulation model is verified by comparing the simulation results with final experiments.The simulation results and experiments reveal that the relation between flapping frequency and driving voltage of motor is approximately linear under various wingspans.The variance of flapping frequency among different wingspans augments gradually with increasing voltage.Furthermore,the simulation results suggest that flapping frequency is sensitive to wingspan and decreases with increasing wingspan of veins,and the relation between flapping frequency and moment of inertia of veins is also approximately linear for various voltages.
基金Project supported by the National Natural Science Foundation of China （Grant No 50205017）.
文摘We have proposed a novel noncontact ultrasonic motor based on non-syinmetrical electrode driving. The configuration of this electrode and the fabrication process of rotors are presented. Its vibration characteristics are computed and analysed by using the finite element method and studied experimentally. Good agreement between them is obtained. Moreover, it is also shown that this noncontact ultrasonic motor is operated in antisymmetric radial vibration mode of B21 mode. The maximum revolution speed for three-blade and six-blade rotors are 5100 and 3700r/min at an input voltage of 20V, respectively. Also, the noncontact high-speed revolution of the rotors can be realized by the parts of Ⅰ, Ⅲ of the electrode or Ⅱ, Ⅳ of the electrode. The levitation distance between the s tator and rotor is about 140μm according to the theoretical calculation and the experimental measurement.
文摘Soft lithography is a low-cost and convenient method for the forming and manufacturing of micro/ nanostructures compared to the traditional optical lithography. In soft lithography, poly（dimethylsiloxane） （PDMS） stamps with relief structures have been widely used to transfer patterns. The traditional fabrication approach of PDMS stamps is time-consuming since the master has been occupied during the curing process. By adding and repeating fast nanoimprint step, many intermediate polymeric molds can be produced from the master and these molds can then be employed to replicate more PDMS stamps while the time used is close to that of the common way. We demonstrated this idea by three masters which were made by the DEM （Deepetching, Electroforming and Microreplicating） and FIB （Focused Ion Beam） techniques. The photos show that the patterns on the PMDS stamps successfully duplicated patterns on the origin masters.
基金Supported by the National High Technology Research and Development Programme of China(No.2007AA04Z340)
文摘A simple autonomous docking method based on infrared sensors for mobile self-reconfigurable relay microrobots is proposed in the paper.The IR guidance system composed of an IR receiver and four IR emitters is designed,analyzed and developed.The autonomous docking control method based on centering alignment and dynamic motion planning is adopted so that it has high efficiency and reliability.Two basic microrobot prototypes are developed,and related docking experiments are done to verify the feasibility of the approach.
基金Project supported by the National Natural Science Foundation of China （No. 30471599） and Development Foundation of Shanghai Science and Technology （No.03ZR14057）.
文摘The interaction between gold nanoparticles and proteins such as bovine serum albumin and immunoglobulin G under the condition of different pH values was studied based on the measurement of zeta potential and fluorescence quenching of the proteins before and after proteins were bound with gold nanoparticles. Aggregations were found in gold colloid aqueous solution after addition of proteins by TEM characterization and UV-Vis spectroscopy deterruination. The results showed that the values of zeta potential were quite different, the binding constant Kb and stoichiometry n were slightly increased with the increase of pH value. In conclusion, two factors could affect markedly the interaction between gold nanoparticles and proteins, that is, surface charge and the coordination effect between gold nanoparticles and indole group of the tryptophan residue of proteins.
基金the National Basic Research (973 Program) (Grant No. 2006CB300406)
文摘In-situ tensile testing in TEM (transmission electron microscopy) is a useful tool for studying mechanical properties of nano-structures because it can provide quanti-tative information on sample deformation at atomic scale. To facilitate in-situ TEM tensile tests of SCS (single crystal silicon) nanobeam, a MEMS tensile-testing chip was designed and fabricated. The chip was fabricated by means of bulk micro-machining and wafer bonding techniques. An SCS nanobeam, a comb drive ac-tuator, a force sensor beam and an electron beam window were integrated into the chip. With the on-chip comb-drive-actuator stretching the nanobeam and in-situ TEM observation, tensile test on a 90 nm-thick nanobeam was performed and the strain-stress relationship was obtained. The Young's modulus was fitted to be 161 GPa and did not show the size effect.
文摘Hydrogenated silicon （Si：H） thin films for application in solar ceils were deposited by using very high frequency plasma enhanced chemical vapour deposition （VHF PECVD） at a substrate temperature of about 170 ℃, The electrical, structural, and optical properties of the films were investigated. The deposited films were then applied as i-layers for p-i-n single junction solar cells. The current-voltage （I - V） characteristics of the cells were measured before and after the light soaking. The results suggest that the films deposited near the transition region have an optimum properties for application in solar cells. The cell with an i-layer prepared near the transition region shows the best stable performance.
文摘Metal-oxide-semiconductor field effect transistor(MOSFET) intrinsic gain degradation caused by channel length modulation(CLM) effect is examined.A simplified model based on Berkeley short-channel insulator-gate field effect transistor model version 4(BSIM4) current expression for sub-100 nm MOSFET intrinsic gain is deduced,which only needs a few technology parameters.With this transistor intrinsic gain model,complementary metal-oxide-semiconductor(CMOS) operational amplifier(op amp) DC gain could be predicted.A two-stage folded cascode op amp is used as an example in this work.Non-minimum length device is used to improve the op amp DC gain.An improvement of 20 dB is proved when using doubled channel length design.Optimizing transistor bias condition and using advanced technology with thinner gate dielectric thickness and shallower source/drain junction depth can also increase the op amp DC gain.After these,a full op amp DC gain scaling roadmap is proposed,from 130 nm technology node to 32 nm technology node.Five scaled op amps are built and their DC gains in simulation roll down from 69.6 to 41.1 dB.Simulation shows transistors biased at higher source-drain voltage will have more impact on the op amp DC gain scaling over technology.The prediction based on our simplified gain model agrees with SPICE simulation results.
基金supported by the National Natural Science Foundation of China(Nos.50730008,60807008)the Doctoral Fund of Hebei Normal University of Science and Technology,China(No.2009YB007)
文摘The selection of solvents for SiC nanowires（NWs） in a dielectrophoretic process is discussed theoretically and experimentally.From the viewpoints of dielectrophoresis force and torque,volatility,as well as toxicity, isopropanol（IPA） is considered as a proper candidate.By using the dielectrophoretic process,SiC NWs are aligned and NW thin films are prepared.The densities of the aligned SiC NWs are 2μm^（-1）,4μm^（-1）,6μm^（-1）,which corresponds to SiC NW concentrations of 0.1μg/μL,0.3μg/μL and 0.5μg/μL,respectively.Thin-film transistors are fabricated based on the aligned SiC NWs of 6μm^（-1）.The mobility of a typical device is estimated to be 13.4cm^2/（V·s）.
