Microchannels transport

Based on the above considerations, Qiakraborty [7] developed a capillary-fiUing model for the transport of blood through microchannels. From his study, following major conclusions were drawn, regarding the implications of the non-Newtonian characteristics on the microchannel transport ... 

Figure 4.7 Reversed symmetrical flow fields are induced by the translation of microdroplets through linear microchannels (transport velocity 7.6mms Y symmetry, mass...

Garimella S, Sobhan C (2003) Transport in microchannels a critical review. Ann Rev Heat Transfer 13 1-50... 

Plam B (2000) Heat transfer in microchannels. In Heat Transfer and Transport Phenomena in Microscale. Banff Oct 54-64... 

Galbiati L, Andreini P (1992) Elow patterns transition for vertical downward two-phase flow in capUlary tubes. Inlet mixing effects. Int Comm Heat Mass Transfer 19 791-799 Garimella S, Sobhan C (2003) Transport in microchannels - a critical review. Ann Rev Heat Transfer 13 1-50... 

Recognizing that the reforming reaction is mass transport limited, the reforming catalyst has been fabricated in microchannel forms which results in significant (factor of 3-5) reduction in the size of the reformer. 

Color Figure 3.7 (A) Enantioselective transport of (S)-ibuprofen by means of ionic liquid flow within a microfluidic device. (B, Bottom) Photographs of the three-phase flow in the microchannel (a) center near the inlets of the microchannel, (b and c) arc of the microchannel, and (d) center near the outlets of the microchannel. Flow rates of the aqueous phase and the ionic liquid flow phase in (a-d) were 1.5 and 0.3 mL/h, respectively. (Reprinted from Huh, Y.S., Jun, Y.S., Hong, Y.K., Hong, W.H., and Kim, D.H., /. Mol. Caial. B, 43,96-101, 2006. Copyright 2006 Elsevier. With permission.)... 

Taking into account typical numbers for a and D, this underlines that the channel width should be considerably smaller than 1 mm (1000 pm) in order to achieve short residence times. Actually, heat exchangers of such small dimensions are not completely new, because liquid cooled microchannel heat sinks for electronic applications allowing heat fluxes of 790 watts/cm2 were already known in 1981 [46]. About 9 years later a 1 cm3 cross flow heat exchanger with a high aspect ratio and channel widths between 80 and 100 pm was fabricated by KFK [10, 47]. The overall heat transport for this system was reported to be 20 kW. This concept of multiple, parallel channels of short length to obtain small pressure drops has also been realized by other workers, e.g. by PNNL and IMM. IMM has reported a counter-current flow heat exchanger with heat transfer coefficients of up to 2.4 kW/m2 K [45] (see Fig. 3). 

Microseparation units make use of the enhancement of mass transport between different phases. PNNL workers reported a microchannel gas-liquid contactor... 

A single neuron-like PC 12 cell was trapped in an etched glass (30 pm deep) pocket sealed against a PDMS channel layer (20 pm). Quantal release of dopamine (in transient exocytosis) from the cell as stimulated by nicotine was amper-ometrically detected with a carbon fiber electrode. The cells flow into the channels caused by the liquid pressure which was provided by a liquid height at the sample reservoir (e.g., 0.5-2 mm). To facilitate transport of cells in the microchannels, the cell density should not be higher than lOVmL. Serious cell adhesion occurred if the transport speed was low (as provided by liquid height below 0.5 mm),... 

Griffiths, S.K., Nilson, R.H., Band spreading in two-dimensional microchannel turns for electrokinetic species transport. Anal. Chem. 2000, 72(21), 5473-5482. 

Yager, P., Cabrera, C., Hatch, A., Hawkins, K., Holl, M., Kamholz, A., Macounova, K., Weigl, B.H., Analytical devices based on transverse transport in microchannels. Micro Total Analysis Systems, Proceedings of the 4th iTAS Symposium, Enschede, Netherlands, May 14-18, 2000, 15-18. 

Figure 5.1 Top a schematic of how to translate the chemical reaction steps of the synthesis of 2-deoxy-2-fluoro-D-glucose into a microfluidic design with microchannels and valves for consecutive fluid transport und manipulation...

A research group at Goteborg University has demonstrated a microfluidic device for combinatorial electrofusion of liposomes and cells [94], Optical trapping was used to transport individual liposomes and cells through microchannels... 

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