Top-down manufacturing

Three top-down manufacturing methods are currently used in micro-fabrication ... 

The top-down manufacturing paradigm is that of the existing electronic technologies. It consists in down-scaling the pattern size in lithographically structured materials. 

Total sales of the fine chemical industry were estimated to amount to about 12 biUion in 1991, by an in-depth analysis of the product portfolio of representative fine chemicals manufacturers (11) and by performing top-down analyses of the fife science industry (12). However, some consulting firms gave higher (- 60 x 10 ) figures for the size of the fine chemicals business (13). 

Nanomaterials can be manufactured by one of two groups of methods, one physical and one chemical. In top-down approaches, nanoscale materials are carved into shape by the use of physical nanotechnology methods such as lithography (Fig. 15.30). In bottom-up approaches, molecules are encouraged to assemble themselves into desired patterns chemically by making use of specific... 

Distinguish between the top down and bottom up approaches to manufacturing nanomaterials. 

Different audit approaches may be applied depending on the intended purpose and scope of the audit. A top-down approach first evaluates the overall structure of the quality system and its subsystems. Selected subsystems may be chosen for review. Systems identified and developed by the FDA in a six-system inspection model for the inspection of drug manufacturers [15] include the following ... 

HCB was neither imported nor manufactured in South Korea. Domestic emission, therefore, should originate from process such as combustion of organic matters combined with chlorine and from impurities in the production of chemicals and pesticides. HCB emission for 2000 in South Korea was estimated in a preliminary study of emission inventory using top-down approach (KMOE, 2003b). Emissions from some sources in 2005 were determined by measuring concentrations in archived samples originally collected for analysis of PCDDs/DFs in 2001-2003 (KMOE, 2005a). 

As different as primitive and modern technologies may seem, they both depend on a "top-down" approach to the manufacture of objects. It begins with a mass of trillions upon trillions of atoms and molecules and uses brute force to arrange those atoms and molecules into some desirable form. 

In this review, we describe the recent developments of chemically directed self-assembly of nanoparticle structures on surfaces. The first part focuses on the chemical interactions used to direct the assembly of nanoparticles on surfaces. The second part highlights a few major top-down patterning techniques employed in combination with chemical nanoparticle assembly in manufacturing two- or three-dimensional nanoparticle structures. The combination of top-down and bottom-up techniques is essential in the fabrication of nanoparticle structures of various kinds to accommodate the need for device applications. 

The limits of the top down and bottom up approaches, illustrated in Fig. 1.5, leave a majority of the nanoworld hard to access. Although constant improvements in technology and chemical synthesis mean that these limits are always shrinking, materials and objects that span the gap between 10 and 100 nm remain hard to fabricate to the level of accuracy and reproducibility expected of most manufacturing techniques. Until recently there was only one way to work on this scale leave it to Nature. 

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