Rapid and low cost replication of complex microfluidic structures with PDMS double casting technology

In this paper, a new method for fast and precise replication of high-aspect-ratio microfluidic structures is reported. First, SU-8 microfluidic structures on the master mold were replicated into Polydimethylsiloxane (PDMS), which served as an intermediate, negative mold, by a conventional soft lithography process. The PDMS negative mold was then treated by wetting its surface with a diluted aqueous solution of a hydrophilic polymer, hydroxypropylmethylcellulose and rinsed with deionized water. Last, the negative mold was used in yet another PDMS molding process to produce a PDMS replica of the microfluidic structures (the hydrofocusing unit for a micro-cytometer) with the same structures as the master mold. Experimental results showed that microstructures with high-aspect-ratio could be consistently replicated with high fidelity. This technique can not only greatly simplify the design and fabrication of master molds, but also protect the expensive and fragile original master mold. The process does not require sophisticated equipment and is well suited for the replication of precision master structures in bulk quantities at low cost.     

探析影响直线振动筛筛分效果的若干因素

本文根据振动筛的运动特点及工作原理,从物料的粒度特性、振动筛运动参数选择、筛分设备性能、激振力调整等多个方面分析了影响筛分效果的因素,总结了影响筛分效果和处理量的原因,并提出了改进措施.     

Preparation and properties of bismaleimide resins of aromatic sulfone ether diamine

Aromatic sulfone ether diamine, bis[4-(4-aminophenoxy)phenyl]-sulfone (SED), was prepared by the nucleophilic aromatic substitution of 4,4′-dichlorodiphenylsulphone by p-aminophenolate. The reaction was conducted in the presence of excess potassium carbonate as a weak base, toluene as the dehydrating agent and N-methylpyrrolidone as the dipolar aprotic solvent. SED showed good solubility in common organic solvents, such as dioxan, tetrahydrofuran, butanone and acetone. SED was reacted with maleic anhydride to obtain aromatic sulfone ether bismaleimide, bis[4-(4-maleimidophenoxy)phenyl]-sulfone (SEM). The compounds were characterized by FTIR and ¹H NMR analysis. Furthermore, copolymer resins of SED with 4,4′-bismaleimidodiphenyl methane (BMI) and SEM were prepared. After curing, crosslinked resins with better thermal stability resulted. The temperature at maximum rate of weight loss (T_max) and the heat-resistant temperature index (T_i) in air were found to be 426°C, 208°C and 579°C, 221°C for BMI/SED and SEM/SED resins, respectively. Compared with the corresponding 4,4′-diaminodiphenyl methane (DDM) system, BMI/SED and SEM/SED showed a slight decrease in T_max and T_i SED-modified BMI/amine resin based glass cloth laminates for printed circuit boards showed higher mechanical properties than those of the corresponding unmodified system. With SED instead of the original amine component in 3–5% weight fraction, the tensile strength, flexural strength and impact strength of the laminates increased markedly. Meanwhile, the stripping strength and weld resistance were also improved by the addition of SED.     

改链条炉为循环流化床锅炉经济效益分析

简介了循环流化床燃烧技术的机理、特征,阐述了循环流化床在化肥厂锅炉应用中的经济效益,指出了循环流化床锅炉改造的必要性。     

上海市工业用地的效率与布局

本文对上海市工业用地的规模、集中度及效率进行了分析,对乡镇工业发展对上海市工业用地布局的影响进行了探讨,在此基础上提出上海工业用地发展的重点;需要解决的问题以及如何更有利地发挥乡镇工业在中国城市化进程中的特殊作用。     

上海郊区农村特色风貌的理解与思考

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电动机无功就地补偿最佳容量配置及节电效果

本文介绍了电动机无功就地补偿技术的节电效果，提出了一种最佳容量配置的简易方法，并列举了本厂补偿测试情况及节能效果。     

Effect of the substrate on the electrodeposition of Bi2Te3−ySey thin films

The potentiostatic electrodeposition of n-type Bi₂Te_3−ySe_y thermoelectric films onto stainless steel and gold substrates from nitric acid aqueous solutions has been carried out at room temperature. The cathodic process during the electrodeposition of Bi₂Te_3−ySe_y films was investigated by cyclic voltammetric experiments. The structure and surface morphology of Bi₂Te_3−ySe_y films deposited on both substrates were characterized by X-ray diffraction (XRD) and environment scanning electron microscopy (ESEM) coupled with energy dispersive spectroscopy (EDS). Electrical and thermoelectric properties of as-deposited films were also measured at room temperature. The results show that the reduction process under the same depositing conditions on gold and stainless steel substrates is very different. On gold substrates, H₂SeO₃ in the electrolyte is firstly reduced to elemental Se, and then the deposited Se reacts with HTeO₂⁺ and Bi³⁺ to form Bi₂Te_3−ySe_y alloy. On stainless steel substrates, HTeO₂⁺ in the electrolyte is firstly replaced by elemental Fe to produce elemental Te, and subsequently the generated Te reacts with H₂SeO₃ and Bi³⁺ to form Bi₂Te_3−ySe_y alloy. Analysis of ESEM show that the surface morphology of the films electrodeposited on gold substrates is more compact than that on stainless steel substrates. The XRD patterns indicate that the films electrodeposited on both substrates exhibit preferential orientation along (1 1 0) plane, but the relative peak intensity of (0 1 5) and (2 0 5) planes on stainless steel substrates is stronger than that on gold substrates. The Seebeck coefficient and electrical resistivity of the films deposited on stainless steel substrates are higher than that on gold substrates.     

基于Arduino的智能循迹小车的设计与实现

以Arduino为主控芯片,以STM32和LDC1000电感数字传感器为小车循迹模块,设计与制作了一个可自动循迹的小车.整个小车系统分为采集、处理、控制三部分:首先,采用LDC1000采集铁丝轨迹信息并将其转化为数字信号传输给数据处理模块;然后,以STM32作为系统处理模块,根据设计的算法处理输入的数据后,再输出不同的...     

新型液晶环氧树脂及其共聚物

介绍了联苯型液晶环氧树脂脂的合成及其与双马来酰亚胺树脂的共聚物。应用红外光谱、ＤＳＣ、热台偏光显微镜对环氧树脂和共聚物的液晶行为进行了表征。经对固化行为研究，得到了共聚物固化反应的活化能和凝胶化的数学模型。