Fabrication of Microchips

Lab-on-a-chip is the miniaturization and integration of the complete set of devices used in separation science. It most important functions involve sample preparation, reactions, separations, and detection on a single chip. This arrangement was called p.-TAS by Manz in 1990 [1]. We call it nanoanalyses as the 

Nanochromatography and Nanocapillary Electrophoresis. By Ali, Aboul-Enein, and Gupta Copyright 2009 John Wiley Sons, Inc. 

Other than the standard cross-t configurations, electrophoretic microchips are not currently commercially available and tend to be fabricated in the laboratories that use them. They can be constructed from glass (Pyrexlike or soda lime), silicon (as per microelectronic chips), or a variety of plastics, or cast from silicone-like materials (polydimethyl-siloxane). The first two of these constitute the vast majority of the electrophoretic devices described in the literature. 

Following successfiil etching, the etched wafer is then bonded to a second piece of glass, into which reservoirs have been drilled, to enclose the chambers and channels of the device. 

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Plastic materials have gained importance in microfabrication due to their ease of molding, inexpensiveness, and disposability. Some workers have used these substrates for fabrication of microchips. Pethig et al. [78] and Roberts et al. [79] used laser ablation as a direct method for creating microchannels in plastic chips without the need for fabrication. The methods used an UV excimer laser to bum the microchannels onto the polymer substrate, moving in a predefined,... 

Molecules interact with the surfaces of solids in almost every environment in the universe. In addition to purely intellectual interest, we customarily justify studying these interactions on technological grounds, heterogeneous catalysis and the fabrication of microchips being the most frequently listed applications. However the field is much more broadly relevant the adsorption and desorption of atoms and molecules on the surfaces of dust grains is very important to molecule formation in the interstellar medium, reactions on the surfaces of ice crystals is important in atmospheric chemistry and reactions at surfaces determine the behaviour of medical implants in our bodies. 

This chapter describes the theory, methodology, and application of a microfabrication process that uses phase-changing sacrificial layers (PCSLs) as intermediates to protect microchannel features during bonding or hydrogel polymerization. We focus on key process details associated with the fabrication of microchips, and the application of PCSL-formed microfluidic devices in CE separations and other electric field-based analysis methods. Finally, we provide a brief overview of potential future trends and applications of PCSL fabrication methods in microfluidics. 

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