微通道反应器在合成反应中的应用

微流控学(microfluidics)是在微米级结构中操控纳升至皮升体积流体的技术与科学,是近10年来迅速崛起的新交叉学科.流体在微流控芯片微米级通道中,由于尺度效应导致了许多不同于宏观体系的特点,例如分子间扩散距离短、微通道的比表面积大、传热和传质速度快等,促进了微流控芯片在有机合成反应中的发展.本文总结了微通道反应器的特点、微通道反应器中常用的流体驱动技术和微通道中流体的混合技术.通过一系列在微流控芯片中进行的有机合成反应,包括液-液均相反应、催化反应、相转移反应和异常激烈的有机合成反应等,进一步说明了微通道反应器同时具有微量和连续流动的优点.微通道反应器的发展不但在合成路线的优化方面有重要意义,而且有助于相关化学工业过程的改进.     

用云纹分析热保护片的静态和动态特性

·本文运用云纹法分析了热保护片的静态和动态特性，同时给出了相应的公式及实验结果     

Construction of Tumor Tissue Array on An Open-Access Microfluidic Chip

An open-access microfluidic chip which enabled automatic cell distribution and complex multi-step operations was developed. The microfluidic chip featured a key structure in which a nanoporous membrane was sandwiched by a cell culture chamber array layer and a corresponding media reservoir array layer. The microfluidic approach took advantage of the characteristics of nanoporous membrane. On one side, this membrane permitted the flow of air but not liquid, thus acting as a flow-stop valve to enable automatic cell distribution. On the other side, it allowed diffusion-based media exchange and thus, mimicked the endothelial layer. In synergy with a liquid transferring platform, the open-access microfluidic system enabled complex multi-step operations involving medium exchange, drug treatment, and cell viability testing. By using this microfluidic protocol, a 10 × 10 tissue arrays was constructed in 90 s, followed by schedule-dependent drug testing. Morphological and immunohistochemical assays results indicated that the resultant tumor tissue was faithful to that in vivo. Drug testing assays showed that the microfluidic tissue array promised multi-step cell assays under biomimetic microenvironment, thus providing an advantageous tool for cell research.     

微流控纺丝制备葡萄糖响应凝胶纤维

葡萄糖响应凝胶纤维在血糖监测传感器开发中有着潜在的应用前景。本文基于微流控纺丝方法和自由基聚合反应制备了化学交联和物理交联的葡萄糖响应聚(N-异丙基丙烯酰胺/3-丙烯酰胺基苯硼酸)(P(NIPAM-co-AAPBA))凝胶纤维。通过傅里叶变换红外光谱、扫描电子显微镜和力学性能测试等技术手段表征了凝胶纤维的结构和形态、力学性能、溶胀度动力学与葡萄糖响应性。结果表明,凝胶纤维具有多孔的微观结构,通过改变芯层与壳层溶液的流速可以调控凝胶纤维的直径。随着AAPBA质量分数的增加,凝胶纤维的溶胀速率和平衡溶胀度均有所降低,但葡萄糖响应性能提高。与化学交联的凝胶纤维相比,物理交联的凝胶纤维具有良好的力学性能。     

Multistage Microfluidic Platform for the Continuous Synthesis of III–V Core/Shell Quantum Dots

We present a fully continuous chip microreactor‐based multistage platform for the synthesis of quantum dots with heterostructures. The use of custom‐designed chip reactors enables precise control of heating profiles and flow distribution across the microfluidic channels while conducting multistep reactions. The platform can be easily reconfigured by reconnecting the differently designed chip reactors allowing for screening of various reaction parameters during the synthesis of nanocrystals. III–V core/shell quantum dots are chosen as model reaction systems, including InP/ZnS, InP/ZnSe, InP/CdS and InAs/InP, which are prepared in flow using a maximum of six chip reactors in series.     

Static adsorptive coating of poly(methyl methacrylate) microfluidic chips for extended usage in DNA separations

A simple and robust static adsorptive (dynamic) coating process using 2% hydroxyethylcellulose was developed for surface modification of poly(methyl methacrylate) (PMMA) microfluidic chips for DNA separations, suitable for usage over extended periods, involving hundreds of runs. The coating medium was also used as a sieving matrix for the DNA separations following the coating process. Four consecutive static treatments, by simply filling the PMMA chip channels with sieving matrix once every day, were required for obtaining a stable coating and optimum performance. The performance of the coated chips at different phases of the coating process was studied by consecutive gel electrophoretic separations with LIF detection using a PhiX-174/HaeIII DNA digest sample. The coated chip, with daily renewal of the sieving matrix, showed high stability in performance during a 25-day period of systematic study, involving more than 100 individual runs. The performance of the coated chip also remained almost the same after 3 months of continuous usage, during which over 200 separations were performed. The average precision of migration time for the 603-bp fragment was 1.31% RSD (n = 6) during the 25-day study, with a separation efficiency of 6.5 x 10(4) plates (effective separation length 5.4 cm).     

In situ and on-line monitoring of hydrodynamic flow profiles in microfluidic channels based on microelectrochemistry: optimization of channel geometrical parameters for best performance of flow profile reconstruction.

A theoretical approach for flow profile reconstruction in a rectangular microfluidic channel equipped with one or two microband electrodes working in generator-collector and generator-generator regimes was proposed by us previously (ChemPhysChem 2005, 6, 1581-1589; ChemPhysChem 2006, 7, 482-487). The purpose of the current study is to determine the ranges of dimensionless parameters corresponding to the highest sensitivity of the minimized functional to the shape of the flow profile. By application of a cubic spline to approximate the flow profile and analysis of the least-squares functional, which can then be represented as a function of one variable, we derive the area of optimal method performance. Thus, mathematical confirmation of our previous theoretical physical predictions could be obtained.     

Physical and Sensory Properties of Japanese Quince Chips Obtained by Osmotic Dehydration in Fruit Juice Concentrates and Hybrid Drying

Japanese quince has high health value, but due to its taste and texture, it is difficult to eat raw. The use of innovative drying methods to produce dried snack foods from these fruits may be of interest to producers and consumers. The physicochemical and sensory properties of 3 mm slices of Japanese quince fruit (with skin, without seeds) obtained by osmotic pre-treatment in chokeberry and apple juice concentrates, and with the use of convection (convective drying, C-D), freeze-drying (F-D), and convection-microwave-vacuum drying (hybrid) are assessed. The methods of drying osmo-dehydrated slices do not affect the dry matter content. In most dried quince, the water activity is 0.40 or lower. Pre-osmotic dehydration and drying have a significant impact on the mechanical and acoustic properties of quince chips. Sensory attractive chips emit loud acoustic emission (AE) during the breaking test. Chips that are osmo-dehydrated in a mixture of chokeberry juice concentrate and sucrose and dried by a hybrid method are attractive. They have a dark red color given by chokeberry concentrate and a slight sweet (with a slight sour-bitter) taste. The sensory evaluation was useful for determining the quality of the chips in terms of their texture (crispness) tested by mechanical methods. Their sensory ratings (overall desirability as weight of color, taste, crispness, and flavor) are high and similar (from 3.8 to 4.1). The use of innovative drying methods with pre-osmotic treatment allows obtaining dried material with properties comparable to those obtained by the F-D method, but in a much shorter time, i.e., with lower energy and using a simple method.     

Mechanically tough dry-free ionic hydrogel microfibers swollen in aqueous electrolyte prepared by microfluidic devices

Soft conducting materials in the shape of microfibers with various functional geometries are crucial for soft electronics. To develop highly stretchable conducting microfibers, a microfluidic method is used to prepare hydrogels in a double-network structure. Based on the coagulation of chitosan in cold water and simultaneous photopolymerization and photocrosslinking of N-isopropylacrylamide and N-diethylacrylamide, long microfibers with controlled uniform diameters can be obtained at the junction of a coaxially aligned microchannel device. After further reinforcement of the chitosan chain and exchange of the medium of the hydrogel microfiber with an aqueous electrolyte of lithium bis(trifluoromethanesulfonyl)imide, the prepared ionic hydrogel exhibits high conductivity and stretchability and dry-free properties. Owing to its mechanical robustness and ionic conductivity, we envision a highly stretchable soft electrode with the prepared ionic hydrogel microfiber that can be stretched up to 900%. This fiber has potential for applications in soft electronics and wearable devices.