Bottom-up manufacturing

Two different approaches to the fabricating of nanostructures have been developed, so called top-down and bottom-up methods [11.5]. The basic principle of agglomeration, the attachment of small entities to similar ones or to other solid surfaces by binding mechanisms (Chapter 3) to form larger units, is used in bottom-up manufacturing. Nanoparticles, having at least one dimension of between 1 and 100 nm, are produced by processes that allow fundamental control over the physical and chemical attributes of molecular-scale structures and are then combined to form larger units with superior chemical, mechanical, electrical, or optical properties. 

Other bottom-up manufacturing methods use self-assembly processes to produce larger structures. If the ambient conditions are right, atoms or molecules spontaneously form ordered arrangements of for example, fullerenes or nanotubes and wires and a quickly increasing array of others, often called nanopartide ensembles [11.6]. 

Madou MJ (2002) Comparison of miniaturization techniques top-down and bottom-up manufacturing. In Fundamentals of microfabrication the science of miniaturization. CRC, Boca Raton, Florida, USA, pp. 402-411... 

Micro-scaling or bottom up approach to quality costs, where it is possible to calculate the cost of losses involved in manufacture and due to returns and/or claims. This method requires a great deal of experience and relies on the availability of detailed cost data throughout a product s life-cycle. While this is a crucial activity for a business, it is also not a practical approach for estimating the quality cost for product in the early stages of product development. 

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. 

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. 

Microfabrication has emerged from microelectronics manufacturing and is using its proven processes and process sequences. Additionally, specific methods have been developed to fabricate mechanical, electrical, optical, or sensor structures, which are characteristics of microfabrication. In order to stay within the scope of this book, only top-down methods, that is, the manufacture of smaller structures with higher functionality from larger structures by the use of subtractive methods, will be discussed. Bottom-up methods, which create larger structures by ordered arrangement of small units (molecules, nanoparticles), are still in their infancy and mainly employed for biosensors. 

Projected emissions from manufacturing industry were estimated from a combination of a bottom-up survey by ICF/BOC and top-down modelling of energy demand by ESRI. 

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