Key Engineering Materials Vols. 562-565

Abstract: Prussian blue nanoparticles (PBNPs) have been certified a kind of mimetic enzyme possesses the advantages of stability, high catalytic activity and low prices. Ferritins are natural nanoscale structures with unique three-dimensional structures and biological functions. In this context, we synthesized PBNPs on the surface of the iron oxide core of ferritin taking use of the ferric iron of the core, we also intended to retain the specificity of ferritin for some biological use. Our results show the resulting nanostructures (Prussian blue-ferritin nanoparticles, PB-Ft NPs) got very small size and relatively high catalytic activity , furthermore, PB-Ft NPs successfully combined the intrinsic enzyme mimetic activity of PBNPs and the specificity to tumor cells of ferritin. The peroxidase-like activity and catalase-like activity of PB-Ft NPs were studied. Peroxidase-like activity which fits well the Michaelis-Menten kinetics was found strongly depending on pH, temperature and the concentration of PB-Ft NPs. Then a sensitive method for glucose detection was developed using glucose oxidase (GOx) and PB-Ft NPs. PB-Ft NPs displayed catalase-like activity in PH higher than 5.0, the generated oxygen was measured by the dissolved oxygen electrode.Enzyme-linked immunosorbent assay (ELISA) shows PB-Ft NPs possess both specificity and peroxidase-like activity.

Abstract: Nanopore and nanopore based biosensing and DNA sequencing have attracted more and more interests in the past ten years. In this paper, a simplified model is addressed to depict biomolecules passing through ultrafiltration membrane (containing nanopores). Based on this model, the passing velocity of biomolecules will not increase continuously but first increase, then decrease and stabilize with the IgG concentration increasing. Due to the physical place-holding effects and the simulation results, it can be predicted that, with biomolecules concentration increasing, the ionic current will first decrease, then increase and finnally stabilize. These predictions based on the simulation match our experimental results well.

Abstract: The real-time monitoring technologies of smart civil structure based on detecting picometer-scale wavelength shift of fiber Bragg grating (FBG), including the wavelength demodulation technology of FBG, are researched extensively at home and abroad. In the paper, using the technologies of wavelength division multiplex (WDM) and time division multiplex (TDM), fiber Bragg grating (FBG) sensor network was built for monitoring smart structure health condition. Based on SOPC (System on Programmable Chip) technology and fiber comb filter, a high-speed and high-precision wavelength demodulation scheme of FBG sensor network was proposed. The optical system and hardware circuit for demodulation system were designed specifically. To improve the accuracy of demodulation system of FBG, a constant temperature channel of the demodulation system connected with a fiber comb filter, which offered reference points to calibrate the Bragg grating center wavelength. Based on 32-bit soft-core processor NoisⅡ, the embedded system collected and processed the photoelectric signal voltage transformed to rectangular voltage pulse. The upper computer displayed dynamically the FBG wavelength demodulation process and calibrated the Bragg grating center wavelength. The experiments of FBG wavelength demodulation and health monitoring of smart structural embedded fiber Bragg gratings were done. Experimental results show that, the FBG wavelength demodulation method can be used to demodulate the FBG wavelength with high speed and high precision (± 2 pm), which can be used extensively in large-scale multipoint monitor engineering, and the strains of the smart structure can be measured accurately.

Abstract: Biomophic ceria with nanocrystalline was successfully synthesized using crucian fish scales as template. Unique biomorphic microstructures were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM) and nitrogen absorption-desorption technique. The obtained ceria material shows the repetitious biomimetic structure consisting of sheet with thickness of ca. 80-100 nm and nanopores which had 2-10 nm apertures. The surface oxygen activity of fish scale-templated CeO₂ was enhanced revealed by hydrogen temperature-programmed reduction (H₂-TPR) mesurements, because of the higher surface area (113.5 m²/g) and smaller particle size (average of 8.2 nm). Those detailed investigation could infer that the biotemplate product exhibit better catalytic activity in CO oxidation reaction.

Abstract: The vapor cells, which contain the simple substrate of alkali metals, are usually the key part of MEMS atomic devices. Alkali metal is extremely active with oxygen and water, making it incompatible with some necessary MEMS process since the instruments are not oxygen-proof. By using paraffin to packet the simple substrate of alkali metals, rubidium for example, the oxidation and deterioration of the metal can be avoided, making it easier to transfer Alkali metals into the vapor cells. It has also been reported that paraffin can serve as a wall-coating material to improve the Q-factor and the long-term frequency stability of the atomic devices. A mold method of manufacturing the package is introduced along with the related key technologies. Laser beam method and needle mold method are discussed to make blind holes on the paraffin wax layer. Paraffin packages containing rubidium simple substrate has been achieved, ranging from 0.9mm3 to 1.6mm3 in size, with the smallest one containing 0.2μL of rubidium inside. The sealing performance of the package has been tested in a one-month (30 days) test and proves to work well by judging from the color of the sealed metal. A low-temperature anodic bonding process is introduced for the fabrication, and absorption spectrum of the vapor cell is obtained, proving that alkali metal simple substrate has been transferred to the vapor cells.

Abstract: Package is one of the key technologies for micro-accelerometer. This paper researched the influence of package on the sensitivity of self-designed piezoresistive accelerometer. Based on the designed package method, the effect of thickness and elastic modulus of die adhesive, package shell materials and signal connection wires on the sensitivity of the sensor were studied by theory analysis, simulation and experimental test. According to results, the sensitivity of micro-accelerometer would be increased with the increasing thickness of die adhesive and decreased with increasing elastic modulus and the quantity of the die adhesive; besides, compared with accelerometer packaged by ceramic shell, the sensitivity of accelerometer packaged with the stainless steel shell was much bigger; meanwhile, the output sensitivity of the sensor varied with length of signal connection wire.

Abstract: Printed circuit boards (PCBs) are being widely used in the electronic packages. Solder joints are often used to interconnect chip resistors and other components onto PCBs. The defects of solder joints will increase quality costs and deteriorate performance. If solder joints cant be located accuracy, AOI system will not inspect solder joints at the right place of solder joints and must lead to misjudgement. Especially, the misjudgement will increase dramatically under uncertain noise disturbance to micro-size solder joints due to inaccuracy location. In this work, an eliminating uncertain noise method is proposed and a robust location algorithm for PCBs solder joints is present. Firstly, some location windows are set based on technology parameters of chip and its solder joints, and solder joints feature image is obtained from it solder joint image based on series of image pre-processing. Secondly, the layout frame outside solder joints, which is viewed as a noise disturbance to location, is extracted as a binary image and is projected to X axis and Y axis, then the smaller region, which include solder joints but no the layout frame, is obtained based on calculating the sum features function of layout frame. Thirdly, the blob feature image of solder joints is extracted from its gray images of red, green, blue layers; it may have some noise blob around solder joints feature, then an evaluation function is develop to judge blob, which maybe belongs to noise or solder joints feature, and only solder joints feature are remained. Fourthly, with the help of setting solder joints windows, the integrated projection method is developed to locate solder joints. Finally, the proposed location method is compared with other two algorithms in the experiment. Experiments result illustrates that the smaller the solder joint size, the better location accuracy and efficiency is obtained than other two mothers.

Abstract: The flow behaviors for polymer melt at the filling stage in micro injection molding are different from those in conventional injection molding due to the miniaturization of plastic parts. This paper focuses on the study of the effects of three main influencing factors, including the microscale viscosity and wall slip, on melt filling flow in microscale neglected those in conventional injection molding process. The theoretical models and the interrelation of these factors in microscale channels were constructed by means of the model correction method. Then, the micro melt flow behaviors were investigated with comparisons of the available experimental data. The results indicate that the dimensions affect the shear rates and viscous dissipation, which in turn affects the apparent viscosity. Finally, the conclusion is that the melt flow behaviors in microchannels are different from those in macrochannels owing to these significant influencing factors.

Abstract: The monolithic integrated technology of MEMS was discussed. First discussed the advantages and difficulties faced by the MEMS monolithic integration technology. Second the features and the process of the mainstream MEMS monolithic integration technology was introduced. And finally put forward a SOI MEMS monolithic integration technology, the technology with no high-temperature process, Post-CMOS integrated solution, compatible with the CMOS process. This technology can achieve high aspect ratio, high-performance micro-inertial devices..

Abstract: In order to improve the ability of magnetic fluid seals, the new structure of crossing magnetic poles on magnetic seals can be designed. The reluctivity of gap with the crossing magnetic pole is less than the reluctivity of gap without the crossing magnetic pole. The magnetic intensity in the gap can be bigger because of the crossing magnetic poles. According to the pressure formula of magnetic fluid seals, the pressure on the one side of magnetic fluid seals can be increased. The sealing capacity with the crossing magnetic pole is more than the sealing capacity without the crossing magnetic pole. The sealing capacity can be improved by 10%-15%.