Silicon micromixer

Floyd TM, Schmidt MA, Jensen KF (2005) Silicon micromixers with infrared detection for studies of liquid-phase reactions. Ind Eng Chem Res 44 2351-2358... 

Woias, P., Hauser, K., Yacoub-George, E., An active silicon micromixer for pTAS applications, in van den Berg, A., Olthuis, W., Bergveld, P. (Eds.), Micro Total Analysis Systems, Kluwer, Dordrecht, 2000, 277-282. 

Many aspects of microreaction technology have been reviewed recently [4]. The unique properties of miniaturized reaction systems have been discussed in the context of production in the multi-kilogram up to ton scale. We at Merck KGaA have tried to apply this technology to the production of fine chemicals [5], triggered by our very early access to a proprietary silicon micromixer [6] with unique mixing properties. 

Because of the expected better workup and disposal procedures, nitration in acetic acid was tried first. Stock solutions of4-(phenyl)morpholin-3-one in glacial acetic acid (2 m) and nitric acid (65%) in concentrated sulfuric acid (4.8 m) were used. For the reaction optimization, two disposable polypropylene syringes (3 mL capacity) were hlled with the different stock solutions and mounted on a syringe pump. The syringes were connected with the silicon micromixer that was connected with a residence time unit, a Teflon tube of known inner diameter and length. The flow of the syringe pump was adjusted according to the residence time required, the only variable. For simplicity, nitrations were carried out at room temperature. 

Fig. 15.4 Silicon micromixer with glued-in hypodermic needles and cast stabilization.

Second Prototype Silicon Micromixer with Connector... 

Woias P, Hauser K, Yacoub-George E (2000) An active silicon micromixer fOT mTAS applications. In van den Berg A, Olthuis W, Bergveld P (eds) Proceedings micro total analysis systems symposium (p,TAS2000), Enschede, The Netherlands, 14—18 May 2000, pp 277-282... 

Figure 2.7 Silicon micromixer chip for high mass flow rates 20 x 20 mm footprint.

P, Woias, K, Hauser, F. Yacoub-George, An Active Silicon Micromixer for mTAS... 

T, Emulsification of silicone oil in water. Comparison between a micromixer and a conventional stirred tank, in Proceedings of the 4th International Conference on Microreaction Technology, IMRET 4, pp. 167-173 (5-9 March 2000), AIChE Topical Conf Proc., Atlanta, USA. 

Schwesinger, W., Erank, T, A static micromixer built up in silicon, in Proceedings of Micromachining and Microfabrication, pp. 150-155, SPIE,... 

Stainless steel is the material of choice for process chemistry. Consequently, stainless steel microreactors have been developed that include complete reactor process plants and modular systems. Reactor configurations have been tailored from a set of micromixers, heat exchangers, and tube reactors. The dimensions of these reactor systems are generally larger than those of glass and silicon reactors. These meso-scale reactors are primarily of interest for pilot-plant and fine-chemical applications, but are rather large for synthetic laboratories interested in reaction screening. The commercially available CYTOS Lab system (CPC 2007), offers reactor sizes with an internal volume of 1.1 ml and 0.1 ml, and modular microreactor systems (internal reactor volumes 0.5 ml to... 

On the other hand, passive chaotic micromixers typically use complex three-dimensional twisted conduits fabricated in various substrates such as silicon [13], polydimethylsiloxane (PDMS) [14], ceramic tape [15], or glass [13] to create 3-D steady flow velocity with a certain complexity to achieve chaotic advection. T q)ical examples of the aforementioned two routes to achieve chaotic advection and mixing in LOC devices are presented in the following. 

In the chemical industry (on the mega- as well as the micro-scale) fine emulsions have many useful applications in, e.g., extraction processes or phase transfer catalysis. Additionally, they are of interest for the pharmaceutical and cosmetic industry for the preparation of creams and ointments. Micromixers based on the principle of multilamination have been found to be particularly suitable for the generation of emulsions with narrow size distributions [33]. Haverkamp et al. showed the use of micromixers for the production of fine emulsions with well-defined droplet diameters for dermal applications [38]. Bayer et al. [39] reported on a study of silicon oil and water emulsion in micromixers and compared the results with those obtained in a stirred tank. They found similar droplet size distributions for both systems. However, the specific energy required to achieve a certain Sauter mean diameter was 3-1 Ox larger for the macrotool at diameters exceeding 100 pm. In addition, the micromixer was able to produce distributions with a mean as low as 3 pm, whereas the turbine stirrer ended up with around 30 pm. Based on energy considerations, the intensification factor for the microstirrer appears to be 3-10. 

The first prototype micromixer was a roughly 1 mm thick silicon plate with the dimensions of ca. 17 X 30 mm (Fig. 15.4). The hrst trivial task to be solved was how to introduce reagents and organic solvents into this micromixer. The first approach was to glue a hypodermic needle onto the silicon chip. The resulting construction was fairly fragile and had to be stabilized by a polymer cast. 

At higher flow rates we observed a drastic rise in the backpressure of the micromixer, which eventually destroyed the silicon body of the mixer. This problem could be overcome by a new mixer-design with parallel channels (Fig. 15.10). The individual mixing structures (Fig. 15.11) were arranged in rows with six split-... 

Fig. 13 Integrated flow microreactor system for the synthesis of block copolymers having two different polymer chains on a silicon core. Ml, M2, M3, M4 T-shaped micromixers R1, R2, R3, R4 microtuhe reactors...

Previously, the fabrication of micromixers was based on microsystem technology or microelectromechanical system (MEMS) technology, which focused on hard materials such as silicon and glass [2]. Recently, polymers have been extensively used for fabricating micromixers. Polymers have several advantages over silicon and... 

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