Microchip fabrication methods

The present chapter will review instrumental aspects for successful coupling of CE with MS, regarding interfaces, ionization sources, and analyzers. Practical considerations concerning different CE modes such as CZE, NACE, MEKC, and CEC coupled with MS will also be discussed and illustrated with a focus on recent pharmaceutical applications. Additionally, quantitative CE-MS will be presented and various methodologies used to achieve sensitive and repeatable analysis will be discussed. Finally, the final section of this chapter will give an overview on new devices (i.e., microchips), hyphenated to MS, in terms of fabrication methods, microchip designs, MS interfacing, and applications. 

Fu et al. [73] used a hybrid device for fabrication and packaging of microchips. This method consisted of a layer of inorganic substrate like silicon wafer and organic elastomer such as PDMS to perform multiple functions on an integrated chip. 

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. 

Optical properties of the material are less critical for microchips hyphenated with MS than for devices with on-chip optical detection where low background absorption or fluorescence is mandatory. Thus, completely opaque polymers like glassy carbon or polyimide " can be used as microfabrication substrates. Furthermore, polymer microchips are of great interest because their potentially low manufacturing costs may allow them to be disposable. Methods used for the fabrication of plastic chips include laser ablation and molding methods. 

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,... 

In fabricating a microchip, why cannot quartz be thermally bonded to glass Name two methods to solve this problem. [844] (4 marks)... 

Chen, Y.H., Chen, S.H., Analysis of DNA fragments by microchip electrophoresis fabricated on poly(methyl methacrylate) substrates using a wire-imprinting method. Electrophoresis 2000, 21, 165-170. 

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