Key Engineering Materials Vols. 531-532

Abstract: An efficient and safe delivery system of RNA interfering is required for clinical application of gene therapy. The study aimed to develop Fe2O3-based nanoparticles for gene delivery to overcome the disadvantages of polyethyleneimine (PEI) or cationic liposome as gene carrier including the cytotoxicity caused by positive charge and aggregation in the cells surface. PEI-capped Fe2O3 nanoparticles are successfully manufactured utilizing Fe2O3 as core, PEI as carapace, which bind miRNA at an appropriate weight ratio by electrostatic interaction and result in well-dispersed nanoparticles. The synthesized GFP tag with miR-26a expression plasmid was used for monitoring transfection efficiency in HepG2 cells. The nanocomplex exhibited higher transfection efficiency and lower cytotoxicity in HepG2 cells than the PEI/DNA complex and commercially available liposome. The delivery resulted in a significantly upregulation of miR-26a in HepG2 cells. Our results offer an alternate delivery system for RNA interfering that can be used on any gene of interest.

Abstract: Stack nanocrystalline-Si (nc-Si) based metal insulator semiconductor memory structure was fabricated by plasma enhanced chemical vapor deposition. The doubly stacked layers of nc-Si with the thickness of about 5 nm were fabricated by the layer-by-layer deposition technique with silane and hydrogen mixture gas. Capacitance-Voltage (C-V) measurements were used to investigate electron tunnel and storage characteristic. Abnormal capacitance hysteresis phenomena are obtained. The C-V results show that the flatband voltage increases at first, then decreases and finally increases, exhibiting a clear deep at gate voltage of 9 V. The charge transfer effect model was put forward to explain the electron storage and discharging mechanism of the stacked nc-Si based memory structure. The decreasing of flatband voltage at moderate programming bias is attributed to the transfer of electrons from the lower nc-Si layer to the upper nc-Si layer.

Abstract: The stability index apparatus is presented, which adopts electrochemical principle and microcontroller technology to determine the solution alkalinity of the circulating water processed by CaCO3. Base on it, this apparatus calculates the stability exponent to evaluate whether the measured water is stable, or existing the tendency of fouling or corrosion. The scaling and the corrosion of pipes and equipments are relieved by controlling the quality of the circulating water. This paper presents the new stability exponent apparatus with which the stability of the water quality can be determined accurately and provides the basis for controlling the water quality. The automatic control of water quality is realized by this apparatus with the cooperation of the dosing system, ensuring the circulating water piping to be safe and stable.

Abstract: The purpose of extracting Macro-model of macro sensor is to find out the mathematical model representing system characteristics of behavior efficiently and accurately. A good understanding of the whole system, collaborative simulation with circuit and optimize system design are meaningful. Whether the extraction of device level Macro- model is truly effective or not, it directly influences the simulation results of system level. Therefore, an effective extraction method of Macro-model is crucial to system simulation. Meanwhile, fast and effective extraction approach for MEMS devices Macro-model will continue to be the main future development of technology. This paper presents a fast automatic extraction technology for Macro-model. Coordinating physical level and system level is to meet the demands of system level fast modeling and simulation.

Abstract: Polypyrrole (PPy) with hierarchical structures inherited from butterfly wings were prepared by using a two-step templating process. Firstly, SiO2 replica was synthesized from butterfly wings by using a sonochemical method and then the obtained SiO2 replica was used as template for the fabrication of PPy with hierarchical structures by using an in situ polymerization method. The precise structues of PPy replica down to nanometer’s level were confirmed directly by FE-SEM, TEM images. The primary response of the replicas to dopamine (DA) as a biosensor was investigated by cyclic voltammetry, and it was found that the PPy replicas showed a much higher biological activity compared with that of common PPy powders, probably due to the hierarchical structures as well as controlled porosity inherited from butterfly wings.

Abstract: A hybrid-structured microfluidic chip integrating optical fiber sensing technology and bioluminescence chemical reaction mechanism was developed for rapid and sensitive detection of adenosine 5’-triphosphate (ATP). This microfluidic chip was fabricated with five distinct layers for the successive steps of sample-enzyme reagent mixing, bioluminescence chemical reaction and scatting light collection. The experimental results demonstrated that the provided hybrid-structure improved the sensitivity, response time, reagent consumption and other properties of chip. This improvement enables the microfluidic chip to attain a sensitive ATP detection in the range from 10^-9 to 10^-4 M with excellent linearity (R² = 0.9967), low detection error (CV < 15%), and tiny reagent consumption (< 20 μL). These achievements thus indicated that the chip developed in this study possess the advantages such as high sensitivity, quick-response and small reagent consumption.

Abstract: In this paper, poly 4-vinylphenol (P4VP)/multi-wall carbon nanotubes (MWNTs) composite film, P4VP/ carbon black (CB) composite film and P4VP/MWNTs multi-layer sensitive films prepared using airbrush technology were deposited on interdigitated electrodes to detect tolunene vapor at room temperature. The surface of the composite film was observed under a scanning electron microscope (SEM). It was found that the resistance of the sensor increased after the exposure to toluene vapor and the increased magnitude of the changes had a good linearity with concentrations of toluene. Meanwhile, the P4VP/MWNTs composite film sensor also has a higher sensitivity than P4VP/CB composite film sensor. P4VP/MWNTs three-layer film sensor was fabricated as well. It was estimated that the response time and recovery time of P4VP/MWNTs three-layer films sensor were about 15 s and 20 s, respectively. The sensor responses of S=0.12% at 10mg/m3 toluene vapor for P4VP/MWNTs three-layer films. The results showed that the multi-layer films sensor exhibited a lower detection limit and better sensing properties compared with the sensors based composite film.

Abstract: UV-LIGA technics which used in high aspect ratio micro-structure fabrication has been developed quickly currently, but there still exist many technical problems which may affect the reliability of production, especially in lithography and electroform process. According to analyzing the technical process of bi-layer micro-gear, the reliability problems have been studied from two aspects, including deep lithography and micro electroform. In the deep lithography technology, the adhesive property between SU-8 photoresist and substrate and the non-uniform thickness and bubble problems of SU-8 photoresist layer have been presented. In the micro electroform aspect, problems include non-uniformity, air holes, and adhesive property of electroformed layer. Aimed at these problems, the resolvents have been put forward and validated, which improve the reliability of technics and possess fine effect.

Abstract: Traditional reliability analysis of MEMS devices is based on only one failure mode, but paroxysmal failure and degradation failure are simultaneous on one MEMS device which is called as competing failure modes. Accelerated degradation modeling and parameter estimation based on competing failure modes are elementary contents of reliability analysis, in which paroxysmal failure and degradation failure are integrated in the process of educing reliability function, and elementary theories of reliability and statistics are used. The method of accelerated degradation modeling and parameter estimation is proved to be precise in a simulation of accelerated life test on a kind of MEMS device which have the two failure modes: paroxysmal failure and degradation failure, and they are have relations with stress variable: current.

Abstract: A prototype of miniature cooling system was developed, which mainly consists of the miniature compressor from DONG YUAN and a spiral-tube evaporator designed by ourselves. The performances of the prototype with different parameters were tested. The influence of ambient temperature, chilled water temperature on the performance of the cooling system were analyzed. The best operating conditions and the optimum amount of refrigerant were obtained. Conclusions were gotten as follows:1) With environment temperature rising, compression ratio increases, system power consumption increases and refrigerating capacity COP decreases. 2) With chilled water temperature rising, compression ratio and power consumption decrease, refrigerating capacity increases, and COP increases rapidly.3) Paper gets system performance: refrigerating capacity is 63 W, compressor power consumption is 24.5 W, COP value is 2.57. in operation condition: refrigerant amount is 40g, environment temperature is 30°C, chilled water temperature is 40 °C, chilled water mass flow is 45 kg/h.