MicroChannel imprinting

FIGURE 51.3 Schematic of the photolithography process to transfer a pattern to a silicon wafer, forming a template for microchannel imprinting. 

Microchannels were also wire-imprinted on Plexiglas using a 90-pm-dia. tungsten wire at 175°C. The channels were triangular-like, typically 200 pm wide... 

Xu, J., Locascio, L., Gaitan, M., Lee, C.S., Room-temperature imprinting method for plastic microchannel fabrication. Anal. Chem. 2000, 72(8), 1930-1933. 

Henry, A.C., Waddell, E.A., Shreiner, R., Locascio, L.E., Control of electroosmotic flow in laser-ablated and chemically modified hot imprinted poly(ethylene tereph-thalate glycol) microchannels. Electrophoresis 2002, 23, 791-798. 

In contrast to columns, the microfabricated devices feature a network of microchannels etched in glass or imprinted in a polymer plate that are designed to enable much smaller sample volumes to be analyzed at an increased speed and permitting a large number of analysis to be performed simultaneously, thus increasing the overall throughput. Microfluidic analytical devices with open channel geometry are currently most frequently used to achieve the desired functions. Open channels are best suited for separation systems in which no interactions with functionalities located at the solid surface are required or are even undesirable, such as in electrophoresis. 

Qu P, Lei JP, Ouyang RZ, Ju HX (2009) Enantiose-paration and amperometric detection of chiral compounds by in situ molecular imprinting on the microchannel wall. Anal Chem 81 9651-9656... 

Kitamura et al. examined the photodegradation of phenol by a silica-supported porphyrin derivative in polymer microchannel chips [15]. With an imprinting method, they fabricate dam-structured microchannel chips. The channels are filled with silica gel particles, which are modified with monopyridyltriphenylporphyrin (PyTPP). The Si-PyTPP particles act as photosensitizers (Scheme 16.9). 

Similarly, many reactors with integrated mixers and other functionality can be manufactured on one substrate to form, e.g., a combinatorial synthesis platform. Such microfluidic platforms may approach the complexity of VLSI electronic circuits, see e.g. [64], which gives an example fabricated by soft lithography (imprinting) in the polymer PDMS or [65], which gives an example in laser-machined laminated Mylar sheets. The combinatorial aspect of these examples consists in mixing chemicals in different ratios to achieve concentration series in a discrete way (i.e. a different concentration for each microchannel) which are subsequently used in a chemical reaction on the same microfluidic chip. 

Pneumatic valves are fabricated using standard microfabrication and assembly technologies. The membrane of the valve can be one uniform film of elastomeric material, or can have microchannels already imprinted on one side (see... 

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