ANSWER ALL PARTS

Answer All Parts

Answer All Parts

a) What are the advantages of miniaturization of analytical instrument? What are technological advancements required to drive miniaturization?

A key benefit of miniaturization is the prospect of integration of all of the steps in an analytical process into a single device. For bench-top analyzers, entire fluidic modules have been machined into transparent plastic blocks to provide both integration and some degree of miniaturization (e.g., UnifluidicsTM Technology, Bayer Corp.). For microchips, the range of components that have been miniaturized and that would be available as building blocks for fully-integrated analyzers is impressive and includes pumps, valves, lamps, filters, heaters, refrigeration, ion-selective electrodes, capillary electrophoresis, and electronic control circuitry. Most devices integrate the different analytical structures by interconnection on the surface of the chip. Three-dimensional integration can be achieved by stacking or by fabricating chips into interconnected layers. Integrating the sample preparation step required in an analytical procedure is an important goal, and white cell isolation from whole blood followed by PCR analysis has been successfully combined on a single 15 mm x 17 mm silicon-glass PCR filter chip. (Michio 1997) Integration of an analytical procedure and detection is possible for a number of assays. For example, restriction fragment length polymorphism analysis can be performed on a glass microchip (~20 mm x 30 mm) that mixes a DNA sample with a restriction enzyme, incubates the mixture, and then delivers the 0.7-nL reaction mixture to an on-chip capillary electrophoresis system for analysis.

About one-third of electronic connectors sold in the United States are printed circuit boards. Cylindrical, rack and panel, planar hermetic sealed, and fiber optic connectors divide the rest of the electronic connector market, with fiber optic connectors showing a strong potential for growth. The demand for increasing miniaturization will drive technological advances in the future. Specialized military and commercial applications will also fuel research. (Kumar 1995)

Citing the failure of solder joints under fatigue as a causative factor in avionics failures, Westinghouse introduced Solder Free Interconnects, secured by cantilever spring clips, and Lockheed Sanders introduced folding printed circuit boards with flexible printed wiring. Although some aspects of the emerging technology made manufacturing less labor-intensive, others, particularly the small size of the components, required heavy investments in specialized machines able to handle the process. (Michio 1997)

(b) What common techniques are used for micro-fabrications? Please include the materials suitable for each fabrication technique.

The data communications market remained one of the largest users of electronic connectors during the 1990s. In particular, private networks in commercial buildings accounted for a significant increase in use of multimode fiber-optic connectors. In an effort to address difficulties during installation of extensive networks (which accounted for a significant amount of the expense when using fiber-optics), traditional epoxy and hot-melt connectors were supplanted by crimp-style connectors. Moreover, at the close of the decade, manufacturers were investigating the possibility of using (no glass) plastic and copper fibers to further reduce cost. (Kumar 1995)

(c) Briefly describe anisotropic etching and isotropic etching ...