Papers by Author: Hai Feng Zhang

Abstract: A novel CMOS interface circuit with high resolution is designed and realized to achieve the integration of interface circuit for liquid suspended rotor micro-gyroscope. The detecting circuit adopts continuous-time current sensing circuit for capacitance measurement. The equivalent output noise power spectral density of phase-sensitive demodulation is 120 nV/Hz1/2. The whole circuitry is realized with 0.5 μm 2P2M CMOS process and its testing results show the circuit has a relative capacitance resolution of 1×10-8, in which the power supply is 18 V and the power consumption is 30 mW. The area of the chip is merely 18.5 mm2.

Abstract: A liquid floating rotational micro-gyroscope is proposed in this paper, whose stability is improved by liquid suspension. High rotor velocity is needed to improve its sensitivity. Edge effect is the phenomenon that sharp edges cause much more viscous drag. This work researches edge effect's influence on viscous drag to speed up the rotor. Flow field models of the sharp edge structure and fillet structure are established separately. Viscous drag is measured by simulation and experiment. Edge effect causes a lot of viscous drag and it can be reduced significantly by filleting the rotor. The maximal reduction is one third relative to the sharp edge structure, and it is reached when fillet curvature radius is half of rotor thickness.

Abstract: In this paper, we make a detail analysis of some factors, which affects the electrostatic bonding process. According to the electrical properties of glass, combined with the principle of electrostatic bonding, we analysed the relationship of critical bonding time, voltage and temperature as well as the factors which affect electrostatic bonding. Then we come up with the mathematical model of the intensity and temperature of electrostatic bonding. In accordance with the above-mentioned formula and the experimental data, we can get the following conclusions: the intensity of electrostatic bonding is much greater between 280°C to 370°C; the best temperature for this bonding is about 350°C; however, when the temperature is below 280°C,the intensity of electrostatic bonding is lower due to the great impact of particles under low temperature; but when the temperature is higher than 370°C,the mismatch of coefficient of thermal expansion of silicon and glass gets larger, then as a result, the intensity of this bonding has a significant decrease with the increasing of temperature.

Abstract: To simulate the whole process of anodic bonding accurately, this paper makes the research on the current of anodic bonding with area and point cathode respectively. Based on the known models of anodic bonding, novel current formulas are deduced for anodic bonding with area cathode by means of the relation between glass resistivity and temperature. After calibrated by statistics of experimental data, the formulas quantitatively describe the relation between bonding current with time, as well as bonding voltage and bonding temperature. Further, using spreading model of anodic bonding, an approach to dealing with the problem of point cathode current is presented. The experiments prove that the current formulas from the approach are able to indicate the law of point cathode current.

Abstract: PMMA, Capillary Electrophoresis, Thermal bonding, Factor, Deformation. Abstract. In this paper, using the powder hot embossing machine, the effects of the bonding temperature, pressure and time on the deformation of microchannel dimensions is studied systematically. The bonding temperature is mainly influence factor on the deformation of microchannel determined by the method of orthogonal experiment. Some mathematical models are described to optimize the thermal bonding process parameters. According theory and experimental curve, the optimal experimental model (83°C, 0.4Mpa and 7 min) is suggested. Under the process parameters the deformation of crossing section dimension before and after thermal bonding is 37.8%. The channel is successfully sealed underneath with a thin foil 30μm thickness PMMA for contactless conductivity detection. The entire fabrication methodology may also be useful for preparation of other polymer microfluidic systems. Finally, the performance of the PMMA chip is demonstrated to separate continuously K+ ions using the contactless conductivity detection.

Abstract: The fracture mechanisms of SiCp/AZ91 composites were investigated by scanning electron microscopy (SEM). For the as-cast composites, the decohesion at SiCp/matrix interface is the main fracture mechanism because of the high stress concentration resulting from the segregation of particles in grain boundaries formed during solidification process. But for the extruded composites, the main fracture mechanism is the particle crack or ductile rupture of the matrix between the particles. So the fracture mechanism of SiCp/AZ91 composites is altered by extrusion because the segregation of particles and defects in the grain boundaries are largely eliminated by extrusion.