Multiphase microfluidics

Govindan CK (2002) An improved process for the preparation of benzyl-n-vinyl carbamate. Org Process Res Dev 6 74-77 Gunther A, Jensen KF (2006) Multiphase microfluidics from flow characteristics to chemical and materials synthesis. Lab Chip 6 1487-1503 Gunther A, Jhunjhunwala M, Thalmann M, Schmidt MA, Jensen KF (2005) Micromixing of miscible liquids in segmented gas liquid flow. Langmuir 21 1547-1555... 

Gunther A, Jensen KJ (2006) Multiphase microfluidics from flow characteristics to chemical and materials synthesis. Lab Chip 6 1487-1503... 

As it will be briefly described in this section, the phenomenology of droplet flows in microfluidic networks can be effectively recovered by simple numerical models [39, 41-43] that assume the generic features of the multiphase microfluidic flows. These very basic models offer an insight into the qualitative features of the dynamics. As the understanding and characterization of the flow of droplets and bubbles in capillaries, junctions, comers etc. progresses, it can be expected that the same simple models, with the appropriate numeric input will able to predict the trajectories of droplets flowing in real microfluidic networks. At the end of this section we provide an example of a quantitative match between experiment and numerical simulation. 

Multiphase interfaces play important roles in microscale transport phenomena. Multiphase microfluidics takes advantages of multiphase interfacial phenomena to achieve various tasks. For example, droplet microfluidics has been used to perform chemical reactions inside droplets for enhanced and accelerated chemical screening... 

Unlike passive multiphase microfluidics, piezoelectric actuators provide the ability to actively control multiphase flow for various microfluidic applications. For example, high-amplitude single-pulse piezoelectric actuation can be used to dispense microdroplets and bubbles on... 

Piezoelectric Actuation in Multiphase Microfluidics, Fig. 1 (a) Schematics of a microfluidic chip for drop-on-demand dispensing. The bottom chamber is filled with an aqueous reagent A piezoelectric bimorph actuator glued to the chamber allows the release of an aqueous drop on demand in the horizontal channel filled with an immiscible fiuid. (b) Description of the experimental setup. The... 

Piezoelectric Actuation in Multiphase Microfluidics, Fig. 7 (a) A microscope image of a lateral cavity acoustic pump with the main channel filled with DI water and polystyrene beads, (b) The pumping pressure generated by a 1-, 5-, and 10-cavity pair device with a maximum input voltage of 25 Vpp. The pressure output is calculated using the measured average flow velocity and the calculated hydrodynamic resistance of the microfluidic system. 

Piezoelectric actuation is a very useful tool for multiphase microfluidics. To fully extract its potential, more quantitative comparison with... 

We start our discussion by emphasizing how flow behavior is related to the transport of molecules and chemical reactions in micrometer- and submicrometer-sized channel networks. We discuss measurement of flow and transport properties and demonstrate how these characteristics translate to a range of diflerent microfluidic applications multiphase flow through porous media [1], human airways [2], miniature cell-biological systems [3, 4], flow in microfluidic catalytic monoUths [5] and the use of interfacial forces as a means for actuation in microdevices [6]. The discussion of multiphase microfluidic systems in this chapter complements several recent reviews on general aspects of transport phenomena in microfluidic systems [37, 174-179]. 

Extrapolating theoretical predictions for axisymmetric studies to non-round channels must be done with considerable care for multiphase microfluidics. For bubbly flows the impact of channel shape is less important. In contrast, for droplet... 

J.D. Tice, H. Song, A.D. Lyon, R.F. Ismagilov, Formation of droplets and mixing in multiphase microfluidics at low values of the Reynolds and the capillary numbers, Langmuir, 2003, 19, 9127-9133. 

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