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Mixing liquids at the micro-scale is difficult because the low Reynolds numbers in microchannels and in microreactors prohibit the use of conventional mixing techniques based on mechanical actuators and induce turbulence. Static mixers can be used to solve this mixing problem. This paper presents micromixers with geometries very close to conventional large-scale static mixers used in the chemical and food-processing industry. Two kinds of geometries have been studied. The first type is composed of a series of stationary rigid elements that form intersecting channels to split, rearrange and combine component streams. The second type is composed of a series of short helix elements arranged in pairs, each pair comprised of a right-handed and left-handed element arranged alternately in a pipe. Micromixers of both types have been designed by CAD and manufactured with the integral microstereolithography process, a new microfabrication technique that allows the manufacturing of complex three-dimensional objects in polymers. The realized mixers have been tested experimentally. Numerical simulations of these micromixers using the computational fluid dynamics (CFD) program FLUENT are used to evaluate the mixing efficiency. With a low pressure drop and good mixing efficiency these truly three-dimensional micromixers can be used for mixing of reactants or liquids containing cells in many microTAS applications. 相似文献
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E. L. Anderson M. M. Thomason H. T. Mayfield W. Bertsch 《Journal of separation science》1979,2(6):335-342
A versatile two-dimensional gas chromatograph is described, consisting of 2 separate ovens, one intermediate trap, an auxiliary inlet, and the necessary hardware to effect off-line switching according to the principle of Deans. The unit has been designed for use with high resolution glass capillary columns. The performance of individual instrumental components was critically evaluated. Results showed that low dead volume glass to metal connections were required in the manifold and detector lines to minimize extra-column effects. The mass of the intermediate trap must be low to allow rapid heating. Operational parameters are discussed and examples of some applications are shown. 相似文献
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W. Bertsch 《Journal of separation science》1978,1(4):187-194
Basic methodology to effect the separation of complex samples by gas chromatography is discussed from an experimental point of view. Several possibilities are presented which are commonly used to enhance the information content of a gas chromatographic run. These include incorporation of more than one set of retention data, multiple detectors, and special column switching techniques. These and other techniques have sometimes been labeled “multidimensional” in the literature. An attempt is made to define the term “two-dimensional chromatography”. The review is divided into sections which point out the different directions which have been taken to deconvolute chromatographically unresolved components. Particular emphasis is placed on technology which is capable of dealing with samples of extreme complexity, and instrumentation for trace- and ultratrace analysis is dicussed with specific examples. The future of two-dimensional techniques in gas chromatography is looked into. 相似文献
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