Micro-flow device

First Large-capacity Numbered-up Micro-flow Devices Reported... 

Chemiker sind der Zelle auf der Spur, Handelsblatt, August 2000 Plant cells as model for micro-reactor development availability of micro-flow devices German leadership first production applications BASF s motivation spotting for DNA arrays materials for micro reactors Merck production plant smallness for efficiency, but not an end in itself [232],... 

The precise definition of residence times for various stages of reactions by introducing reactants in a spatially confined manner in micro flow devices allows new ways... 

Behavior of the fluids in the microfabricated channels are different from those in the millimeter scale channels. Miniaturization of micro flow devices opens a new research field, microfluidics which represents the behavior of the fluid in the micro channel [8]. Since the Reynolds number in the micro channel is usually below 200, the flow is laminar and special design concepts are necessary for the fluidic elements of mixers, reaction coils etc. in the pTAS. Some components of flow switches and fluid filters were developed using laminar flow behavior. 

Micro/Nano Fabrication Technologies and Micro Flow Devices for Future Energy Devices... 

In this session, micro direct methanol fuel cells (DMFC) fabricated by Si MEMS and plastic MEMS are described. For examples of micro/nano fabrication technologies, fine micro plastic fluidic chips fabricated by molding and low temperature bonding are reported. The 3-D metal micro mesh electrode fabricated by simple UV photolithography is described next. For an example of micro flow devices, the pneumatically actuated microvalve and the microreactor having multireagent inlets are introduced. 

The details of the specific features of the heat transfer coefficient, and pressure drop estimation have been covered throughout the previous chapters. The objective of this chapter is to summarize important theoretical solutions, results of numerical calculations and experimental correlations that are common in micro-channel devices. These results are assessed from the practical point of view so that they provide a sound basis and guidelines for the evaluation of heat transfer and pressure drop characteristics of single-phase gas-liquid and steam-liquid flows. 

Numerous researchers have studied damage to micro-organisms during flow in pipes, (Fig. 11) [87,88] Most researchers use a Fanning friction factor, f, to calculate the energy dissipation rate for fully developed flow in tubular bioreactors and capillary flow devices. There are minor differences in the equations that are used but they are generally of the following form [89,901 ... 

Strictly, chemical micro processing, in addition to being a device field based on micro channels, is a means to use micro flows, which is oriented not at one, but rather at a multitude of purposes. Process intensification, also strictly, is a concept (but specifying no concrete means) and apparatus for a specific purpose (see above). 

Micro Total Analysis Systems (pTAS) are chip-based micro-channel systems that serve for complete analytics. The word Total refers to the monolithic system character of the devices, integrating a multitude of miniature functional elements with minimal dead volumes. The main fields of application are related to biology, pharmacology, and analytical chemistry. Detailed applications of pTAS systems are given in Section 1.9.8. Recently, pTAS developments have strongly influenced the performance of organic syntheses by micro flow (see, e.g., [29]). By this, an overlap with the micro-reactor world was made, which probably will increase more and more. 

One of the most far reaching analyzes along these lines of thought was given by Commenge [114] in the context of gas-phase reactions in continuous-flow processes. Specifically, he analyzed four different aspects of micro reaction devices, namely the expenditure in mechanical energy, the residence-time distribution, safety in operation, and the potential for size reduction when the efficiency is kept fixed. 

The key attribute of flows in micro devices is their laminar character, which stands in contrast to the mostly turbulent flows in macroscopic process equipment. Owing to this feature, micro flows are a priori much more accessible to a model description than macro flows and can be described by first-principle approaches without any further assumptions. In contrast, for the simulation of turbulent flows usually a number of semi-heuristic models are applied, and in many situations it is not clear which description is most adequate for the problem under investigation. As a result, it stands to reason to assume that a rational design of micro reactors... 

Micro-flow processing is not an exclusive domain of micro-channel devices made by micro fabrication. This approach can be applied to any packing of regular-shaped objects which results in interstices of the same internal dimensions and the same precision as given for micro channels. Obviously, interstices made from extended, but thin objects resemble best the nature of micro channels. Hence the use of filaments for constituting a micro-flow assembly was recently described [8]. 

It is to be expected that in the near future more of such concepts will find application, simply for cost reasons. Laboratory-scale investigations with precisely microfabricated reactors in advance of the use of such devices can give valuable information, providing a best-case scenario. From then, one can look for alternative micro-flow solutions of lower cost, higher reliability, higher flexibility and so... 

This class of hybrid components comprises chip micro-reactor devices, as described in Section 4.1.3, connected to conventional tubing. This may be H PLC tubing which sometimes has as small internals as micro channels themselves. The main function of the tubing is to provide longer residence times. Sometimes, flow through the tube produces characteristic flow patterns such as in slug-flow tube reactors. Chip-tube micro reactors are typical examples of multi-scale architecture (assembly of components of hybrid origin). 

Figure 4.30 Electrochemical micro reactor, a diaphragm micro flow cell, applied to perform the cation flow method. Assembled device (left). Disassembled device showing the two compartments of the cell within the housings and the diaphragm (right) [67. ...

This sheet micro flow reactor (Figure 4.32) was used for investigating spatially two-dimensional effects in reaction media using agar gel induced by electric fields [68]. This device utilizes an adapted Petri dish which comprises a rectangular channel... 

These are total systems or even plants made for parallel automated organic synthesis, typically in the liquid phase. In this section, no commercial devices (typically not relying on micro flow processing) are considered, but rather only specialty apparatus developed in the framework of chemical micro processing. 

The Menschutkin reaction was carried out as a test reaction to show the feasibility of such novel micro flow concepts that allow to process fouling-sensitive reactions (see also Section 4.2.6 here another test reaction is decribed for the same purpose) [78]. The reaction of alkyl bromide with ternary bases such as pyridine or triethylamine gives quaternary salts insoluble in most solvents. Often, fairly rapid precipitation of this salt occurs, hence ideally serving as a test reaction for fouling sensitivity of micro-channel devices. The reaction of 4,4 -bipyridyl and ethyl bromoacetate [78] belongs to the category of fast-predpitating Menschutkin reactions, as the halide function is activated by the carbonyl fimction. 

Micro reactors are continuous-flow devices consuming small reaction volumes and allowing defined setting of reaction parameters and fast changes. Hence they are ideal tools for process screening and optimization studies to develop solution-based chemistries. 

The liquid enters the micro channel device via a large bore that is connected to a micro channel plate via a slit (Figure 5.2). The slit acts as a flow restrictor and serves for equipartition of the many parallel streams [1, 3, 4]. The liquid streams are re-collected via another slit at the end of the micro structured plate and leave the device by a bore. The gas enters a large gas chamber, positioned above the micro channel section, via a bore and a diffuser and leaves via the same type of conduit. 

The naming of the micro channel device stems from the prevailing flow pattern related to the guidance bubbles through a continuous liquid medium [3,9,... 

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