Micro-and Nanofabrication Techniques

However, each currently developed method has its own disadvantages. Hard-template methods, for instance, are a universal and controlled approach to obtaining conducting-polymer nanostructures, but the requirement of a template and the post-treatment for template removal not only results in a complex preparation process, but can also destroy the formed structures. Moreover, the size and morphology of available templates is limited. The soft-template method is another relatively simple, cheap, and powerfid approach to obtain CPCs via a self-assembly process. However, the morphology and size control of the self-assembled nanostructures obtained is poor. Therefore, finding a facile, efficient, and controlled route to prepare CPs nanostructures is desirable. 

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The use of micro- and nanofabrication techniques for the directed synthesis and construction of biological structures, such as artificial organs and hybrid devices, presents a wide spectrum of opportunities for research and applications. Applications such as development of cell-based arrays, microfabrication-mediated tissue engineering, and the development of artificial organs using micro- and macro-scale construction techniques are some of the many very exciting possibilities on the horizon. 

As mentioned earlier, while DPN techniques present novel opportunities for the direct patterned deposition of materials at feature sizes that would either be difficult or significantly more expensive using other standard micro- and nanofabrication techniques, DPN is still limited to small-scale research applications at this point. This limitation is due in large part to the fact that useful feature writing using passive cantilever probes is either Not possible at speeds which are practical for many potential larger-scale applications. 

In summary, modeling offers powerful tools and guidance for performance optimization. With advancements in new techniques for micro- and nanofabrication, it will be possible to engineer fuel cell CLs (electrodes) according to the compositions and structures predicted by modeling and simulation. 

Defects in SAMs The density of defects in SAMs may ultimately determine the usefulness of the materials in micro- and nanofabrication [77]. Although SAMs are representative self-assembling systems and tend to reject defects, formation of defects in these systems is inevitable because the true thermodynamic equilibrium is never achieved in the preparation of a SAM. A variety of factors have been found to influence the formation and distribution of defects in a SAM, including the molecular structure of the surface, the length of the alkyl chain, and the conditions used to prepare the SAM [78]. A range of techniques have been employed to... 

The above discussions have highlighted the utility of both magnetic arrays and colloidal-templated crystals for DNA electrophoresis. While the variety of solid supports that can be fabricated by these techniques is limited when compared to those available through micro- and nanofabrication, the ease with which these self-assembled arrays can be constmcted confers significant advantages... 

The basic difference between conventional processing and nanofabrication is the dimension of the structures to be fabricated. There are basically two possible approaches top-down and bottom-up approaches. In the top-down approach, micro and nanostructures are achieved by controlled removal of extra amount of material by applying an external source of energy such as mechanical, thermal, chemical, and electrochemical energy. The top-down approach of micro and nanofabrication is schematically shown in Fig. 1.2. This approach is difficult to apply at nanoscale however at microscale, it has been utilized successfully by various means. In the bottom-up approach, positions of atoms or molecules are manipulated to build up the nanodevices or nanostmctures, as illustrated in Fig. 1.3. Various techniques of this approach are under development at the laboratory level and need further improvements. 

Soft Lithography Soft lithography represents a non-photolithographic strategy based on self-assembly and replica molding for carrying out micro and nanofabrication [4]. It has been mostly developed in recent years. It is a favorable process for researchers to build nanometer-scale structures. It includes the following techniques ... 

Distinct methods and strategies to tailor polymeric substrates with topographical signals have been discussed in this chapter. From the extensive work developed by many researchers and summarized here, it is evident that the majority of the studies has been performed onto 2 D surfaces, mainly due to the limitation of the fabrication techniques. Further and continuous advances in micro- and nanofabrication, as well as other technologies are under development. It is expected that by applying these technologies it would be possible to translate the advanced 2D models into 3D structures with such a high structural and hierarchical complexity that could mimic more efficiently the in vivo environment. 

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