Characteristic Features of Microflow Systems

The characteristic features of microsystems stem from the small size of the space in the microstructures. Therefore, microsystems are not necessarily small systems in total size. They can be large in total size as long as they contain microstructures that can be used for chemical reactions. This sharply contrasts with the concept of a lab-on-a-chip, which should be small in total size. It is also important to note that microsystems are normally set up as flow-type reactors with a constant flow of solutions through a microstructured reaction chamber or channel. Although the reactor s capacity at any one time is small, total production capacity over time is much greater than may be imagined. Therefore, microflow systems are not necessarily used solely to produce small quantities of chemical substances. In fact, a microfluidic device has been developed that fits in the palm of the hand but can produce several tons of a product per year (see Chapter 10). 

Stemming from the small sizes and high surface-to-volume ratio of the microstructures, microflow systems composed of microfluidic devices have the following characteristic features (Table 7.2)  

Fast mixing because of the small diffusion path Short residence time 

Precise temperature control (fast heat transfer) Fast mass transfer at the phase boundary 

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Examples of flash chemistry that take advantage of characteristic features of microflow systems will be demonstrated in the following chapters. 

Oxidation and reduction using chemical, electrochemical and biochemical methods are attained by virtue of characteristic features of microflow systems. Microflow... 

Cationic polymerization without stabilization of a carbocationic intermediate can be carried out in a microflow system. Good molecular weight control and molecular weight distribution control are attained by virtue of characteristic features of microflow systems (microflow-systempolymerization technology, MCPT). Conventional controlled/living cationic polymerization based on cation stabilization can be also carried out in a microflow system. 

The principles and examples of flash chemistry using microflow systems have been discussed in the previous chapters. Microflow systems serve as an effective method for the control of fast reactions. Extremely fast reactions can be conducted without deceleration in a highly controlled manner by virtue of characteristic features of microsystems, such as fast mixing, fast heat transfer, and short residence time. Synthetic reactions can be much faster when they are released from the restriction of a flask. 

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