Silicon-based Microreactors

Fig. la-e. Selected microreactors, a Stainless steel microreactor system designed by Ehrfeld Mikrotechnik. b Glass microreactor (Watts and Haswell 2005). c Stainless steel microreactor of the CYTOS Lab system (http //www.cpc-net.com/cytosls.shtml). d Silicon-based microreactor designed by Jensen (Ratner et al. 2005). e Glass microreactor of the AFRICA System... 

Hansen CL, Skordalakes E, Berger JM, Quake SR (2002) A robust and scalable microfluidic metering method that allows protein crystal growth by free interface diffusion. Proc Natl Acad Sci USA 99 16531-16536 Herzig-Marx R, Queeney KT, Rebecca JJ, Schmidt MA, Jensen KF (2004) Infrared spectroscopy for chemically specific sensing in silicon-based microreactors. Anal Chem 76 6476-6483... 

Silicon-Based Microreactor Systems Silicon is one of the most common materials that have been used for various MEMS devices. Silicon has a high elastic modulus (130-180 GPa) with small thermal expansion and low intrinsic mechanical loss and relatively good chemical compatibility [7]. The surface of the silicon can be easily modified by oxidation to form an oxidized silicon microreactor which is functionally... 

Jensen KF (2005) Silicon-based microreactors. ACS Symp Ser 914 2-22, Chapter 1... 

Figure 10.2 Silicon-based microreactors (a) microchannel reactor [19] and (b) membrane microreactor [20].

Figure 10.1 Optimization of glycosylation reactions with the use of a silicon-based microreactor...

The first study of the epoxidation of cyclohexene in a silicon-based microreactor was reported by Basheer et al. (2006). Due to a low solubility of cyclohexene in the phosphate buffer reaction media, ionic liquid l-butyl-3-methylimidazolium tetrafluoroborate ([BMIMJpFJ) was introduced (0.5 % v/v) to the buffer solution. The performance of four various types of catalysts such as Schiff-base and reduced Schiff-base complexes of Cu(II) and Mn(ll) complexes were investigated. The T-shaped microfluidic channel was filled with phosphate buffer solution of ionic liquid and 5 % of the Schiff catalysts. The reactant was introduced to the microchannel, driven by a difference in the electric potential between the inlet and the outlet of the microchannel. Catalytic activity and yields were foimd to be relatively high for the Cu (II) complexes as compared with those obtained with conventional bulk scale epoxidation. 

Basheer, C., Vetrichelvan, M., Suresh, V., Lee, H. K. (2006). Ionic-liquid supported oxidation reactions in a silicon-based microreactor. Tetrah. Lett, 47, 6, (February 2006) 957-961, ISSN 0040-4039... 

Jackman, R.J., Queeney, K.T., Herzig-Marx, R., Schmidt, M.A., Jensen, K.F., Integration of multiple internal reflection (MIR) infrared spectroscopy with silicon-based chemical microreactors. Micro Total Analysis Systems, Proceedings 5th Y7AS Symposium, Monterey, CA, Oct. 21-25, 2001, 345-346. 

The heart of the system is a microreactor packaging scheme that is based upon a commercially available microchip socket. This approach allows the silicon-based reactor die, which contains dual parallel reaction channels with more than 100 electrical contacts, to be installed and removed in a straightforward fashion without removing any fluidic and electronic connections. Various supporting microreactor functions, such as gas feed flow control, gas feed mixing, and various temperature control systems, are mounted on standard CompactPCI electronic boards. The boards are subsequently installed in a commercially available computer chassis. Electrical connections between the boards are achieved through a standard backplane and custom-built input-output PC boards. A National Instruments embedded real-time processor is used to provide closed-loop process control and... 

The influence of wall film on the RTD in segmented flow was studied in detail by Kuhn et al. [23]. The authors used microreactors with a square section of 0.4 X 0.4 mm and a length of 750 mm. The walls of the silicon-based microdevices were modified by growing a thin silicon oxide layer to get a hydrophilic surface... 

We will not consider here the large domain of silicon-based microdevices (including silicon nitrides and carbides), which would hardly be considered for fuel processing at the industrial level due to the cost of the substrate material. A general literature review and detailed information on silicon technology-based microreactor... 

Novel microreactors with immobilized enzymes were fabricated using both silicon and polymer-based microfabrication techniques. The effectiveness of these reactors was examined along with their behavior over time. Urease enzyme was successfully incorporated into microchannels of a polymeric matrix of polydimethylsiloxane and through layer-bylayer self-assembly techniques onto silicon. The fabricated microchannels had cross-sectional dimensions ranging from tens to hundreds of micrometers in width and height. The experimental results for continuous-flow microreactors are reported for the conversion of urea to ammonia by urease enzyme. Urea conversions of >90% were observed. 

Biochemical analysis on nanoliter scale is precisely carried out by micrototal analysis system (pTAS) which consists of microreactors, microfluidic systems, and detectors. Performance of the pTAS depends on micromachined and electrochemically actuated micropump capable of precise dosing of nanoliter amounts of liquids such as reagents, indicators, or calibration fluids [28]. The dosing system is based on the displacement of the liquid from a reservoir which is actuated by gas bubbles produced electrochemically. Electrochemical pump and dosing system consist of a channel structure micro-machined in silicon closed by Pyrex covered with novel metal electrodes. By applying pulsed current to the electrodes, gas bubbles are produced by electrolysis of water. The liquid stored in the meander is driven out into the microchannel structure due to expansion of gas bubbles in the reservoir as shown in Fig. 11.8. 

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