Microtechnology-based systems

The high compatibility of microtechnology-based processing with process analytics means that not only is it very convenient to do process monitoring but also to study the chemical process with the equipment. Mills and coworkers [8] recently described a gas-phase microtechnology-based system for the characterization of catalysts. The integrated system that contains the process analytics needed for reaction characterization demonstrates that high-quality data can be obtained from laboratory-based systems. 

This system includes several mixing and heat exchange units. A concept for an integrated, microtechnology-based fuel processor was proposed by PNNF [8]. As examples for unit operations which may be included in future integrated systems the same publication mentions reactors for steam reforming and/or partial oxidation, water-gas shift reactors and preferential oxidation reactors for carbon monoxide conversions, heat exchangers, membranes or other separation components. 

In a general sense, the characterization of the performance of the microtechnology-based equipment is not a process analytical problem and is the responsibility of the hardware developer since there are many variables that need to be characterized for proper design and operation of the device. These include flow distribution to the multiple channels, chemical component mixing and heat transfer rates, to name just a few. For example, Schouten has demonstrated the care needed to characterize and model gas-phase reactor systems that he and his colleagues design (e.g. [6]). 

Normally, filtering would also need to be done, but this seems to be less of a problem as the whole system requires particle control to avoid problems with the small chaimels in the microtechnology-based processing equipment. Still, some type of filter on the analytical stream is recommended as particles can originate from the sampling system itself... 

The advantage for the microtechnology-based equipment is that the high degree of compatibility means that inclusion of the analysis system from the start is very easy. 

Another feature of the NeSSI approach is that since there is easy control of the flow path, it is possible to mount or connect the microtechnology-based processing equipment to the backbone system. This makes it easy to have the analyzer components in the system for analysis as soon as the reaction pathway is designed. Some users have actually integrated the chemical processing and the analyzer components on to the same NeSSI backbone system whereas others have just interconnected the two types of flow systems. Either approach makes it easy to have signiflcant flexibility available to characterize a reaction. 

Extensive signals behave in an additive manner. In consequence, it is not possible to measure extensive signals such as mass or volume in small parts of a system, and therefore sensors for extensive signals cannot easily be miniaturized. For sensors based on microtechnologies, which are normally preferred for mass production due to cost considerations, extensive signals are difficult to handle because there is often no simple level of standardization for batch-oriented fabrication processes. How this problem may be solved is shown in the next section. 

Owing to participation of Latvian and Swedish scientists in the field of chemically sensitive FET and MOS structures it was possible to utilize the technological facilities of the Microelectronics enterprise in Latvia in making an integrated smart sensor as a matrix of chemically sensitive FETs by using silicon based microtechnology Thereby the first steps of pTAS in Latvia are made in the direction of integration of solid state ionic materials with FET and MOS structures to develop new chemically sensitive structures and systems... 

Stevenson, C. L. Santini Jr. J. T. Langer, R. Advanced Drug Delivery Reviews. 2012. in press doi 10.1016/j.addr.2012.02.005. Reservoir-Based Drug Delivery Systems Utilizing Microtechnology. 

There are different points of view regarding device size and fluid quantity for the definition of microfluidic device. The microelectromechanical systems (MEMS) terminology indicates that the device size must be smaller than 1 mm. Electrical and mechanical engineers are interested to work on microfluidics because of their fabrication capabilities using microtechnology. Their idea is to shrink the device size and thus define microfluidics in terms of size to take advantage of the new effects and better performance. The objective is to shrink down the pathway of the chemicals. Another preferred way to define microfluidics is based on fluid quantities. Figure 1.1 (a,b) shows fhe size and volume characteristics of different microsystems. 

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