Micromixer active

Figure 2.2 A simple fabrication process of active electrokinetically driven micromixers, (a) BOE etching, (b) electron beam evaporation of gold/chromium, (c) gold/chromium etching, (d) cover drilling, and (e) alignment and bonding [62].

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. 

An active mixer based on an oscillating EOF induced by sinusoidal voltage ( 100 Hz, 100 V/mm) was devised and modeled for mixing of fluorescein with electrolyte solutions. This is termed as electrokinetic-instability micromixing, which is essentially a flow fluctuation phenomenon created by rapidly reversing the flow. Various microchips materials (PDMS, PMMA, and glass) and various electrolytes (borate, HEPES buffers) have been used to evaluate this method of micromixing [480]. 

The activity of [i-galactosidasc (P-Gal) was studied on a quartz chip using a static micromixer to mix the enzyme and substrate on the ms time scale. Inhibition by phenylethyl-P-D-thio-galactoside was also studied [1048]. In another report, the enzyme P-Gal was assayed on a chip in which P-Gal would convert a substrate, resoruhn-P-D-galactopyranoside (RBG), to resoruhn to be detected fluorescently [1049]. By varying the substrate concentrations and monitoring the amount of resoruhn by LIF, Michaelis-Menten constants could be determined. In addition, the inhibition constants of phenylethyl-P-D-thiogalactoside, lactose, and p-hydroxymercuribenzoic acid to the enzyme P-Gal were determined [1049]. 

Yang, Z., Goto, H., Matsumoto, M., Maeda, R., Active micromixer for microfluidic systems using lead-zirconate-titanate(PZT)-generated ultrasonic vibration. Electrophoresis 2000, 21, 116-119. 

Choi, J.-W., Hong, C.-C., Ahn, C.H., An electrokinetic active micromixer. Micro Total Analysis Systems, Proceedings 5th pTAS Symposium, Monterey, CA, Oct. 21-25, 2001, 621-622. 

Johnson, B.J. (2003). Flash nanoprecipitation of organic actives via confined micromixing and block copolymer stabilization. Ph.D. dissertation, Princeton University, Princeton, NJ. 

The concept of flash chemistry can be applied to polymer synthesis. Cationic polymerization can be conducted in a highly controlled manner by virtue of the inherent advantage of extremely fast micromixing and fast heat transfer. An excellent level of molecular weight control and molecular-weight distribution control can be attained without deceleration caused by equilibrium between active species and dormant species. The polymerization is complete within a second or so. The microflow system-controlled cationic polymerization seems to be close to ideal living polymerization within a short residence time. 

V. Flessel, FI. Lowe, F. Schonfeld, Micromixers-a review on passive and active mixing principles, Chem. Eng. Sci. 60 (2005) 2479. 

Various active micromixers using 2-D time-dependent flow to achieve chaotic advection have been developed [16-19]. Since electroosmosis is very attractive for manipulating fluids in LOC devices, a chaotic electroosmotic stirrer developed by Qian and Bau [20] is described as an example to achieve chaotic advection and mixing by 2-D time-dependent electroosmotic flow. 

Keywords Active micromixers Microfluidics Micromixing Mixing principles Passive micromixers... 

As described previously, active micromixers rely on an external energy input to introduce perturbation within the fluid streamlines to achieve mixing. Therefore, they are categorized with respect to the type of external perturbation energy ... 

One of the simple ways to achieve active mixing is to induce a pressure field disturbance. Active micromixers relying on this strategy have been reported from different authors [43, 156-159], Deshmuck et al. [156, 157] proposed a T-junction microfluidic chip with an integrated micropump that alternatively drives and stops the flow within the microdevice to create a segmented flow. 

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