Key Engineering Materials Vols. 609-610

Abstract: The finite element method to obtain the stiffness of MEMS (Micro-Electro-Mechanical Systems) accelerometer is difficult to give an exact expression, so a new method to analyze the stiffness of MEMS accelerometer was purposed. Both Mechanics and electricity analysis were used to calculate the stiffness of vacuum microelectronic accelerometer developed in our laboratory, and the control and detection circuits were design according to the result. Finally, the sensitivity, linearity and other performance were measured through the static gravitational field experiments; the least squares curve fitting correlation coefficient 0.9999 and linear 0.9%. The result shows that this method to analyze the stiffness of the stiffness of vacuum microelectronics accelerometer is correct and feasible, and this method can also be applied to other MEMS accelerometer with symmetrical structure and electrostatic force balance mode.

Abstract: Electrode jump motion strategy was adopted to fabricate noncircular tool using wire electrical discharge grinding (WEDG). The machining procedure and electrode jump motion strategy for noncircular tool fabrication were determined through experiments. This approach has been verified by successfully machining of rectangular electrode (38μm×38μm, 700μm length) and D-shaped electrode (diameter 45μm, height 42μm, 500μm length). D-shaped array holes of 6×6 matrix were drilled using corresponding single noncircular tool which was manufactured by the adopted machining approach. The array holes have tight diameter tolerance and height tolerance which are both less than 2μm, and positioning errors are both less than 1μm in the direction of the X, Y-axes.

Abstract: Sigma-delta ADC outperforms the Nyquist ADC in precision and robustness by using oversampling and noise shaping. A fourth-order sigma-delta modulator of input feedforward architecture is designed and simulated in system-level. Input feedforward architecture has advantages of low output swing of integrators and simple structure. Proper circuit parameters are also presented in this paper. The simulation revealed that the modulator achieves 109 dB dynamic range in a signal bandwidth of 1 KHz with a sampling frequency of 250 KHz.

Abstract: This paper proposes a novel dual-extended nanostructure memristor model compared to HP memristor can be called Single-extended memristor. Oxygen ions and oxygen vacancies all are effective carriers in this memristor as the structure are made of TiO_2-x/TiO₂/TiO_2+x three nanolayers between Pt electrodes.The sample of dual-extended memristors arrays were fabricated by ways which these cost-effective methods can be exploited to produce memristors with nanoscale electrode width. Dual-extended nanostructure memristor model will be represented and the mechanism will be discussed. Fabrication methods of the memristor device are introduced and the electronic characteristics are measured and plotted. The results are discussed will experimentally demonstrated that higher switching speed and lower power will be gained by using dual-extended memristors to design IC.

Abstract: This paper reports an effective design method for optimizing the geometric parameters of a micronozzle. Numerical analysis is conducted to predict the propulsion performance of micronozzles. By means of design of experiment (DOE), the number of numerical experiments is reduced dramatically from 1024 to 16. The interaction effects of the geometric parameters are taken into consideration for the first time. The results indicate that the interaction effects of geometric parameters cannot be neglected in choosing the optimal parameters for a practical design.

Abstract: A fabrication process to manufacture SU8 photoresist microstructures is presented in which BP212 positive photoresist was used as sacrifice layer and SU8 was used as structure layer. No crack has been observed in the obtained microstructures. The relation between PEB temperature and stress gradient in SU8 film has been studied by measuring radii of released SU8 cantilevers made at different PEB temperatures.

Abstract: The off-axis parabolic mirror plays more and more important role in high-tech areas since the advantages of reducing space and improving the quality of imaging. Two ultra-precision manufacturing methods are often applied to machining the off-axis ellipsoidal mirror, which one is revolving the cylindrical blank around the axis of ellipsoidal surface and another one is revolving around the axis of cylindrical surface. But which machining method can produce a better result has no rounded comparisons and analysis according to previous research. In this paper, the tool path generation method is presented and the corresponding tool paths of each manufacturing method for the off-axis ellipsoidal mirror are calculated respectively. The motion characteristics are also analyzed and compared correspondingly. Finally, the effects of diamond tool parameters are further analyzed in theory to avoid the tool interference. The studies processed in this paper provide a theoretical basis of choosing the ultra-precision manufacturing method for the off-axis ellipsoidal mirror and can improve the efficiency and precision of processing.

Abstract: During ultra-precision cutting of brittle materials, the wear of diamond tool seriously affects the quality of machined surface. By molecular dynamics modeling of nanometric cutting, the generation of graphitization and its formation process at the cutting edge of tool are observed. By analyzing the process, the reason of the graphitization wear is mainly thermo-chemical reactions. By calculating the changes of coordination numbers of the tool atoms, graphitization conversion rate keeps increasing along the cutting process but gets stable after a certain length, which indicates the graphitization wear will occur in the same process.

Abstract: The neural probe array is an important tool for getting the neural signals. Giving consideration to the biological compatibility and the demand of integrating in circuit, new fabrication process of a silicon-based three-dimension neural probe array was reported. The idea about milling in mechanical process and the method of structure for transfer were introduced in the fabrication. The 10*10 scale silicon-based three-dimension probe arrays integrated in the readout circuit directly were fabricated by means of flip chip and multi-blade mixing dicing techniques. In the entire fabrication process, no any high-temperature process and silicon wet etching process, which would damage the circuit, were included. Using the fabrication process above, the 10*10 scale silicon-based probe arrays with centre-to-centre separation of 400 μm were achieved. In the probe arrays, whose good rate was more than 95%, the width of a single probe was 100 μm, the tip angle was 25o, and the height was more than 1.4 mm. Through the fabrication process, it was not only reducing the pin count greatly, but also simplifying the interface effectively. By the in vivo experiment of the Sprague Dawley rat, the corresponding nerve signal was obtained.

Abstract: This paper puts forward a kind of two benches structure of the glass-PDMS free flow electrophoresis chip. We use die casting method to produce microstructure, and use PDMS as its structure layer. The mold is made in tape-PMMA by micro cementing technology. During the progress of PDMS curing, gold wires are directly integrated in the electrode groove to form the chips electrodes. PDMS and glass are sealed in natural bonding method. Chips glass surface of separation chamber realizes the modification through sticking polyimide tape. Visual technology is conducted for chip electrophoresis separation. The sample is the mixture of methyl green and Rhodamine B. The separation effect of methyl green and Rhodamine B is obvious when the electric field is 31 V/cm. the "two benches" between the electrode groove and the separation chamber block the electrolytic bubbles into the separation chamber. When the separation chamber height is 70 μm and the electric field is 50 V/cm, the air bubbles can be glidingly discharged from electrode groove. The samples steady separation time is more than 2 hours, and this free flow electrophoresis chip realizes continuous work.