Microflow systems, chemical applications

Recent progress in microflow devices and systems is described in this chapter. Examples of passive and active flow control methods applicable in practical pTAS are described in Sect. 2. Multiple flow control systems, i.e., arrayed microvalves, for advanced high-throughput microflow systems are then introduced in Sect. 3. Examples of microflow devices and systems for chemical and biochemical applications are described in Sect. 4. 

A variety of p-, m-, and o-disubstituted benzenes were synthesized in one flow at much higher temperatures than those required for conventional batch reactions. Industrial application of fine chemicals is envisaged after increasing productivity of this microflow system [72] (Figure 11.20). 

W-Methyl-A/ -nitroso-p-toluenesulfonamide (MNTS) is an important precursor for the production of diazomethane. Diazomethane is then further converted to a range of useful molecules in the pharmaceutical and fine chemical industry [69]. Production of MNTS is a highly exothermic process and includes the presence of the extremely toxic materials. Stark et al. [70] have explored the application of microreactor technology for the production of this industrially valuable material, assuming that due to the efficient heat exchange and the closed system, microflow conditions provide a safer environment for these hazards. 

Microflow Devices and Systems for Chemical and Biochemical Applications... 

Recent advances in the fabrication of microflow devices using MEMS technology are described from the technological point of view. The flow control methods and multiple flow control systems reported here are applicable in efficient chemical microreactors as well as in chemical analysis systems. For high-performance flow device design, computational dynamics (CFD) simulation is indispensable. The... 

An understanding of multiphase microflows is critical for the development and application of microstructured chemical systems in the chemical industry. As one of the most important meso-scientific issues, interfacial science could be a bridge connecting microscopic molecular components and macroscopic fluid behaviors in these systems. Working together with viscous and inertial forces, the interfacial force also dominates complicated multiphase flow patterns and well-controlled droplets and bubbles. In this review, the generation mechanisms of different flow patterns and the break-up rules for droplets and bubbles in microchannels are introduced first. The effects of the adjustable fluid/solid interfaces, or so-called wetting properties, of microchannels on multiphase flow patterns, as well as microchannel surface modification methods, are then discussed. The dynamic fluid/fluid interfaces in multiphase microflows with variable... 

Microflow or low-flow nebulizers, which were described in greater detail in Chapter 3, are being used more and more for routine applications. The most common ones used in ICP-MS are based on the microconcentric design, which operate at sample flows of 20-500 pL/min. Besides being ideal for small sample volumes, the major benefit of microconcentric nebulizers is that they are more efficient and produce smaller droplets than a conventional nebulizer. In addition, many microflow nebulizers use chemically inert plastic capillaries, which makes them well suited for the analysis of highly corrosive chemicals. This kind of flexibility has made low-flow nebulizers very popular, particularly in the semiconductor industry, where it is essential to analyze high-purity materials using a sample introduction system that is free of contamination." ... 

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