Editorial

Microtechnology in Chemical Engineering

The ongoing development in micro and nano technology and the increasing power of inte-grated circuits have driven a technical revolution in industry and everyday life. Recent auto-mation, computing and communication are based on micro chip technology. Beside electro-nic devices where electrons only are operated, micro fabrication also allowed to buildminiaturized transducers for signal transformation. But behind information handling andmeasurement technologies, the fields of microfluidics and micro reaction technologyopened the toolbox of micro fabrication for the manipulation and conversion of matter. Dur-ing the last two decades, micro reaction technology was established as a part of chemical en-gineering with fast increasing scientific and practical importance. Meanwhile it is much morethan an exotic experimental field and more than an extension of chemical micro sensorics: Itbrought micro scale devices and new principles in to the industry and continuous-flow chem-istry from the industrial scale back in to the labs. It improved the control of process condi-tions for many synthesis, enhanced the yields and the turn over per time. In particular, it isable to realize extreme reaction conditions and enables chemical engineers to design com-plete new process protocols. The promising perspectives of strongly improved performancesand completely new strategies in process design give good arguments for accepting moresophisticated arrangements and higher requirements for the quality of reactants, the actua-tion of fluids and the monitoring of process parameters. The challenges and advantages ofmicrotechnology in chemical engineering and lab applications have been in the focus of the5th international workshop on microlaboratory techniques held in Ilmenau/Elgersburg inFebruary 2010. Selected presentations related to some key issues of microtechnology in che-mical engineering are presented in this focus issue of Chemical Engineering & Technology.The set of papers give a representative impression of the recent state of the art. Empirical op-timization and process development are more and more based on understanding of physicalparameters and can be described by models of fluid dynamics and for the transport of massand heat.The advantages of fast and well-controlled heat transfer can be used in synthetic aswell as analytical procedures and separations. The heat transfer can be adapted to the speci-fic requirements by well-designed geometry and material choice in microsystems. Heat fluxand time constants can be estimated by thermal modeling and simulation and support theoptimization of processes and micro devices (e.g., Q. Wang et al. in this issue). The under-standing of local convection and mass transfer in slugs and the optical control with high spa-tial resolution gives the basis for well-controlled reactions under slug-flow conditions, for ex-ample in case of the synthesis of aluminium oxid and metal/carbon hybrid particles (A. Uferet al.). The management of interfaces and the control of transport and mixing can be used forthe synthesis of high quality nanomaterials, in particular oxidic nanopowders. A very highhomogeneity of CaCO3- and ZnO-powders can be achieved by continuous-flow synthesis in aSegmented Flow Tubular Reactor (A. Aimable et al.). The power of micro reaction technologyis due to the highly reproducible local convection conditions and a very narrow residencetime distribution resulting in an extreme homogeneity of reaction conditions in all volumeelements. Meanwhile, the residence-time distribution as a key parameter for chemical engi-neering can also be characterized and explained for homogeneous fluid conditions. It can beshown that tracer methods for experimental investigation can be applied and the applicationof appropriate models lead to an understanding of residence time distribution of differentmicroreactors of complex fluidic structures (D. Boskovic et al.). Beside chemical reactions,microfluidics gives the unique opportunity for the manipulation and characterization of nanoand micrometer-sized objects. The power of electrokinetic methods for mobility characteriza-tion in microchannels was demonstrated for the example of classification of microorganisms(L. D. Garza-Garcia). The recent state of research and the progress in the understanding andpractical applications of microtechnology in chemical engineering is not only very encoura-ging for the intensification of the further development of micro reactors, but confirm the par-ticular power of microtechnology for realizing new types of engineering solutions in a largespectrum of processes. The synthesis of inorganic and organic substances, but in particularthe management of heterogeneous systems, of droplets and particles benefit from the un-derstanding of fast local mass and heat transfer, from precise definition of process condi-tions, from fast feed-back loops for process control, from the enormous potential of processintensification and the realization of new process windows and from the possibility of imple-mentation of multi-step continuous-flow processes.

www.cet-journal.com © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Chem. Eng. Technol. 2011, 34, No. 3, 330–330

Michael Köhler,Technische Universität Ilmenau,Institut für Physik

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