Microfluidic components

The realization of complete bench-scale micro reactor set-ups is certainly still in its infancy. Nevertheless, the first investigations and proposals point at different generic concepts. First, this stems from the choice of the constructing elements for such set-ups. Either microfluidic components can be exclusively employed (the so-caUed monolithic concept) or mixed with conventional components (the so-called hybrid or multi-scale concept). Secondly, differences concerning the task of a micro-reactor plant exist. The design can be tailor-made for a specific reaction or process (specialty plant) or be designated for various processing tasks (multi-purpose plant). 

Branebjerg, J., Fabius, B., Gravesen, B., Application of miniature analyzers from microfluidic components to pTAS, in van den Berg, A., Bergfeld, P. (Eds ), Micro Total Analysis Systems, Kluwer, Dordrecht, 1995, 141-151. 

Abstract In sensor and microfluidic applications, the need is to have an adequate solvent resistance of polymers to prevent degradation of the substrate surface upon deposition of sensor formilations, to prevent contamination of the solvent-containing sensor formulations or contamination of organic liquid reactions in microfluidic channels. Unfortunately, no comprehensive quantitative reference solubility data of unstressed copolymers is available to date. In this study, we evaluate solvent-resistance of several polycarbonate copolymers prepared from the reaction of hydroqui-none (HQ), resorcinol (RS), and bisphenol A (BPA). Our high-throughput polymer evaluation approach permitted the construction of detailed solvent-resistance maps, the development of quantitative structure-property relationships for BPA-HQ-RS copolymers and provided new knowledge for the further development of the polymeric sensor and microfluidic components. 

Microfabrication technology used to manufacture microreactors also introduces many advantages, most notably the ability to rapidly and cheaply mass-produce devices. The low cost of microfabricated devices makes it possible for these devices to be disposable, a characteristic desirable for many medical applications. Rapid scale-up of production by operating many microreactors in parallel can also be accomplished. Microfabrication also presents the opportunity for complete systems in a single monolithic device or systems on a chip as microreactors are incorporated with chemical sensors and analysis devices, microseparation systems, microfluidic components, and/or microelectronics. 

This short summary shows that there is the potential for many novel applications and improvements over the state-of-the-art within the above-mentioned criteria of sensitivity, cost, time, and size. However, despite a myriad of publications about microfluidic components, principles and applications, very few successful products with a relevant market share have emerged from this field so far. In the next chapter, we will outline probable reasons and present emerging paradigm changes for the future research in microfluidics. 

S. L. Neale, M. P. Macdonald, K. Dholakia, and T. F. Krauss, All-optical control of microfluidic components using form birefringence. Nature Materials 4 p. 530-533 (2005). 

Laurell, T, Marko-Varga, G., Ekstrom, S., Bengtsson, M., Nilsson, J., Microfluidic components for protein characterization. Rev. Mol. Biotechnol. 2001,82(2),... 

Integratable Microfluidic Components Based on GERF Microvalves. 103... 

This review summarizes the research achievements concerning integration of biosensors into microfluidic chips, which have been reported mostly since 2005. We discuss the latest developments by categorizing them on the basis of four different aspects detection principles, analytes, functional receptors, and microfluidic components. Based on a balanced view of recent trends, the review is concluded by looking at the future perspectives in this field. 

The micromixer is an essential microfluidic component for specific applications. Compared with conventional macroscale mixers, micromixers need a somewhat different approach to working principle, specification, and design. First of all, it is hard to make turbulence in such a limited volume [285, 286]. And, more than two solutions in a microfluidic system are necessarily mixed as rapidly as possible for... 

Real world synthetic problems are rarely solved in one step, but are more normally addressed by a combination of factors leading to complex solutions. The plug and play nature of microfluidic components makes them a flexible tool in problems of this nature, even when the whole process in question cannot be transferred onto a single microfluidic device. The following seetion outlines some illustrative examples of such applications. 

Other microfluidic components have also been developed using static electrowetting. An electrowetting-actuated valve was proposed by Cheng and Hsiung [10]. A hydrophobic layer comprising plasma-modified poly... 

Microfluidic component assembly Microfluidic integration Microfluidic systems assembly Microfluidic systems packaging... 

Mechanical joints for assembling microfluidic components and systems often involve insertion of one part into another. The aforementioned cartridges are a simple example, and structures must be included on both the cartridge and inside the instrument to allow smooth insertion. Such structures can include micro-rails to aid such sUding assembly on-chip. Care must be taken in choosing materials for properties such as friction and wear. Friction is deflned as the force of motion or tendency toward such of two surfaces in contact, defined by the equation ... 

Schomburg WK, Volhner J, Bustgens B, Fahrenberg J, Hein H, Menz W (1994) Microfluidic components in LIGA technique. J Micromech Microeng 4 186-191... 

Fig.1 Illustration of microfluidic components in typical lab-on-a-chip device...

Edwards TL, Mohanty SK, Edwards RK, Thomas CL, Frazier AB (2002) Rapid micromold tooling for injection molding microfluidic components. Sens Mater 14 167... 

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