Transitional Microchannels

Transitional channels Transitional microchannels Transitional nanochannels Nanochannels ... 

Moiini GL (2004) Laminar-to-turbulent transition in microchannels. Microscale Thermophys Eng... 

Rands C, Webb BW, Maynes D (2006) Characterization of transition to turbulence in microchannels. Int J Heat Mass Transfer 49 2924-2930 Ren L, Qu W, Li D (2001) Interfacial electrokinetic effects on liquid flow in micro-channels. Int J Heat Mass Transfer 44 3125-3134... 

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... 

Taitel Y, Bamea D, Dukler AE (1980) Modeling flow pattern transitions for steady upward gas-liquid flow in vertical tubes. AlChE J 26 345-354 Triplett KA, Ghiaasiaan SM, Adbel-Khalik SI, Sadowski DL (1999a) Gas-liquid two-phase flow in microchannels. Part 1 two-phase flow patterns. Int J Multiphase Flow 25 377-394 Triplett KA, Ghiaasiaan SM, Abdel-Khalik SI, LeMouel A, McCord BN (1999b) Gas-liquid two-phase flow in microchannels. Part 11 void fraction and pressure drop. Int J Multiphase Flow 25 395 10... 

Flow is typically laminar in microchannel devices, although not always rigorously so. Correlations for fully developed laminar flow in perfectly rectangular microchannels have been validated in the literature [33-35]. Transition and turbulent flows in a microchannel have no such consistent treatise, and are highly dependent upon channel shape, aspect ratio, and surface characteristics [36, 37]. 

For most medium- and large-scale micromanifold structures, where one passage feeds multiple parallel channels, flow traverses through turbulent and transition flows in the micromanifold region. This fluid in turbulent to transition flow also turns in the micromanifold region as it drops flow into parallel microchannels, which are primarily in the laminar flow regime. 

While ionization by linearly polarized fields has been well studied, there is only one report of ionization by a circularly polarized field, the ionization of Na by an 8.5 GHz field.36 In the experiment Na atoms in an atomic beam pass through a Fabry-Perot microwave cavity, where they are excited to a Rydberg state using two pulsed tunable dye lasers tuned to the 3s — 3p and 3p —> Rydberg transitions at 5890 A and —4140 A respectively. The atoms are excited to the Rydberg states in the presence of the circularly polarized microwave field which is turned off 1 fis after the laser pulses. Immediately afterwards a pulsed field is applied to the atoms to drive any ions produced by microwave ionization to a microchannel plate detector. To measure the ionization threshold field the ion current is measured as the microwave power is varied. 

Affinity chromatography of streptavidin was performed on a PET chip. The microchannel was first filled with the dual-modified latex beads (as shown in Figure 6.3). The biotinylated beads were surface-modified with a temperature-sensitive polymer, poly(N-isopropylacrylamide (PNIPAAm, 11 kDa). When the temperature was raised above the lower critical solution temperature (LCST) of PNIPAAm, the beads aggregated and adhered to the channel wall, because of a hydrophilic-to-hydrophobic phase transition. Then streptavidin from a sample solution was captured by these adhered biotinylated beads. Thereafter, when the temperature was reduced below the LCST, the beads dissociated and eluted from the channel wall together with the captured streptavidin [203],... 

FIGURE 8.33 Erythrocytes flowing through microchannels with background subtraction applied to the images. Single, double, and triple transits are observed in some of the microchannels [304]. Reprinted with permission from IEEE. 

The microchannel plate (MCP) remains the detector of choice for many TOF-MS applications because of its large, flat active area high gain and excellent time response. Typical rise times of MCP devices are unparalleled transitions from 10% to 90% of peak intensity are routinely on the order of picoseconds [34]. Often, two microchannel plates are oriented back to back in what is termed a chevron arrangement to achieve gains of 106 or greater, each plate contributing about 103. Mi-... 

In the laminar and transition regimes in microchannels, the behavior of convective heat transfer coefficient is very different compared with the conventionally-sized situation. In the laminar regime, Nu decreases with increasing Re, which has not been explained. 

The Nu in the laminar and transition regimes in microchannels is correlated with Br, in addition to Re, Pr, and a geometric parameter of the microcharmels. The role of Br in the laminar regime is supported by an analysis of the experimental data. 

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