Surface microchannel

Alternatively, microchip technologies offer other platforms for HTS such as microarrays and microfluidic devices. Microarrays allow the simultaneous analysis of thousands of parameters within a single experiment and for this reason have become cracial tools in drug discovery and life sciences research. They consist of immobilized biomolecules spatially addressed on planar surfaces, microchannels or microweUs, or an array of beads immobilized with different biomolecules. Biomolecules commonly immobilized on microarrays include oligonucleotides, polymerase chain reaction (PCR) products, proteins, lipids, peptides, and carbohydrates. Currently, in situ synthesized microarrays can be purchased or... 

C.-J. Kuo, Y. Peles, Local measurement of flow boiling in structured surface microchannels, Int. J. Heat Mass Tranfer, 2007, 50, 4513 526. 

Figure 1.1 Different examples of spontaneous capillary flows (SCF) in open-surface microchannels (channels etched in sihcon and coated hy an SiO layer) (a) serial SCF (b) parallel SCF (c) parallel channels (d) winding channels crossing wells (e) filling of a cylindrical cavity (f) capillary filaments in a cylindrical well (g) capillary filaments in corners. Photographs by N. ViUard, D. Gosselin and J. Berthier (CEA-Leti).

Judy J, Maynes D, Webb BW (2002) Characterization of frictional pressure drop for liquid flows through micro-channels. Int J Heat Mass Transfer 45 3477-3489 Kandlikar SG, Joshi S, Tian S (2003) Effect of surface roughness on heat transfer and fluid flow characteristics at low Reynolds numbers in small diameter tubes. Heat Transfer Eng 24 4-16 Koo J, Kleinstreuer C (2004) Viscous dissipation effects in microtubes and microchannels. Int J Heat Mass Transfer 47 3159-3169... 

Ou J, Perot B, Rothstein JP (2004) Laminar drag reduction in microchannels using ultrahydrophobic surfaces. Phys Fluids 16(12) 4635 643... 

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]. 

The surface tension is of great importance when dealing with bubbles and particulate contaminations in microchannels and determining how strong the capillary forces are in a microchannel. For a cylindrical cross-section, the capillary force, Fcap, can be expressed quantitatively as shown in the following equation,... 

Adding additional surface. Whilst a high ratio of surface to volume is inherent in an empty/open micro-channel, this characteristic may be further pronounced by packing micro-beads in the channel (He et al. 2004). The introduction of beads within microchannels can introduce some practical difficulties, but a number of successful applications using this type of methodology have been described (He et al. 2004 Nikbin and Watts 2004). 

Another way to use silicon wafers as DLs was presented by Meyers and Maynard [77]. They developed a micro-PEMFC based on a bilayer design in which both the anode and the cathode current collectors were made out of conductive silicon wafers. Each of fhese componenfs had a series of microchannels formed on one of their surfaces, allowing fhe hydrogen and oxygen to flow through them. Before the charmels were machined, a layer of porous silicon was formed on top of the Si wafers and fhen fhe silicon material beneath the porous layer was electropolished away to form fhe channels. After the wafers were machined, the CEs were added to the surfaces. In this cell, the actual diffusion layers were the porous silicon layers located on top of the channels because they let the gases diffuse fhrough fhem toward the active sites near the membrane. 

T. Kawakatsu, G. Tragardh, C. Tragardh, M. Nakajima, N. Oda, and T. Yonemoto The Effect of Hydrophobicity of Microchannels and Components in Water and Oil Phases on Droplet Formation in MicroChannel Water-in-Oil Emulsification. Colloid and Surfaces A Physicochem. Eng. Aspects 179, 29 (2001). 

I. Kobayashi, M. Nakajima, and S. Mukataka Preparation Characteristics of Oil-in-Water Emulsion Using Differently Charged Surfactants in Straight-Through MicroChannel Emulsification. Colloid Surfaces A Physicochem. Eng. Aspects 229, 33 (2003). 

SIP-driven polymer brush library fabrication leverages the fact that the polymerization initiation species are permanently bound to the substrate. Since the initiators are tethered, controlled delivery of monomer solution to different areas of the substrate results in a grafted polymer library. In NIST work, initiators bound via chlorosilane SAMs to silicon substrates were suitable for conducting controlled atom transfer radical polymerization (ATRP) [53] and traditional UV free radical polymerization [54, 55]. Suitable monomers are delivered in solution to the surface via microfluidic channels, which enables control over both the monomer solution composition and the time in which the solution is in contact with the initiating groups. After the polymerization is complete, the microchannel is removed from the substrate (or vice versa). This fabrication scheme, termed microchannel confined SIP ([t-SIP), is shown in Fig. 10. In these illustrations, and in the examples discussed below, the microchannels above the substrate are approximately 1 cm wide, 5 cm long, and 300-500 [tm high. 

Fig. 10 Illustrations of the microchannel confined surface-initiated polymerization (p-SIP) route for producing gradient polymer brush libraries a route for making polymer molecular weight and block copolymer libraries b route for making statistical copolymer libraries. Red arrows show the flow of monomer solution from a syringe pump used to gradually fill the microchannel. See text for details...

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