Miniaturization, limits

Since the first demonstration that DNA can act as a scaffold for metallization to produce conducting wires [270], the proposal to create circuits on a nanometre size scale has appeared achievable. With CMOS technology predicted to reach a miniaturization limit by 2012 [271], and the high cost and low throughput associated with nanometre scale scanning probe and electron beam lithographic top-down techniques, the DNA-templated synthesis of wires with widths typically less than 50 nm may provide a scheme to cir-... 

Table 4-S. Established miniaturization limits for measurement and control components [Maier 1990],...

Miniaturization limits for single-chamber micro solid oxide fuel cells with coplanar electrodes. J. Power Sources, 194 (2), 941-949. 

A phenomenon known as silver migration has limited the use of silver plating in miniature circuit boards under a positive d-c potential within a damp environment silver can migrate across insulation. On drying, silver is found in the insulation or media creating a leakage path. Silver plating is forbidden in many military specifications for circuit boards. 

A type of miniature globe valve, needle valves are used in instrument systems for throttling of small volumes. They have metal to metal seats, but due to the small size, can be used for positive shut-off (Figure 15-8). Needle valves have small passageways that may plug easily and limit their use to very small flow rates. 

The eytoplasm is a viscous fluid and contains within it systems of paramount importance. These are the nucleus, responsible for the genehc make-up of the cell, and the ribosomes, whieh are the site of protein synthesis, hi addihon are found granules of reserve material suehas polylydioxybutyric add, an energy reserve, and polyphosphate or volutin granules, the exact funchon of which has not yet been elucidated. The prokaiyohc nueleus or bacterial chromosome exists in the cytoplasm in the form of a loop and is not surrounded by a nuclear membrane. Bacteria cany other chromosomal elements episomes, which are portions of the main chromosome that have become isolated firm it, and plasmids, whieh may be called miniature chromosomes. These are small annular pieees of DNA whieh carry a limited amount of genetic information. 

Rinard dedicated his research to a detailed analysis of methodological aspects of a micro-reactor plant concept which he also termed mini-plant production [85] (see also [4, 9, 10] for a commented, short description). Important criteria in this concept are JIT (Just-in-time) production, zero holdup, inherent safety, modularity and the KISS (keep it simple, stupid) principle. Based on this conceptual definition, Rinard describes different phases in plant development. Essential for his entire work is the pragmatic way of finding process solutions, truly of hybrid character ]149] (miniaturization only where really needed). Recent investigations are concerned with the scalability of hybrid micro-reactor plants and the limits thereof ]149], Expliddy he recommends jointly using micro- and meso-scale components. 

An impressive example of the impact of miniaturization on the explosion limit has been given for the oxyhydrogen reaction [18]. For a conventional reactor of 1 m diameter, explosive behavior sets in at 420 °C at ambient pressure (10 Pa). An explosion occurs at about 750 °C, when the reactor diameter is decreased to about 1 mm. A further reduction to 100 pm shifts the explosive regime further to higher pressures and temperatures. 

WolfA. Microreactors,newefficient tools for optimumreactor design, in Microtechnologies and Miniaturization, Tools, TechniquesandNovel Applications fortheBioPharmaceuticalIndustry, IBC Global Conferences limited, London (1998). 

Micro reaction systems may help to overcome or at least reduce some of the above-mentioned limitations [69]. Electrochemical micro reactors with miniature flow cells where electrodes approach to micrometer distances should have much improved field homogeneity. As a second result of confined space processing, the addition of a conducting salt may be substantially reduced. In addition, benefits from a uniform flow distribution and efficient heat transfer may be utilized. 

In the first two contributions electroanalytical techniques are described for application in bioanalysis and medicine. The increasing interest in this field is mainly due to the excellent selectivities and detection limits. In addition, the possibilities of miniaturization allow the development of in vivo analysis. 

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