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Applications ranging from state-of-the-art lithography in the semiconductor industry to molecular electronics require the control of polymer structures on length scales down to individual molecules. Structures on nanometer length scales can be achieved by employing a “bottom-up” approach, in which individual molecules are assembled to form a structural entity [1]. By using bottom-up technologies it is, however, by no means trivial to interface the macroscopic world. Technologies that are applied in practice usually require the modification and control of structures extending from the smallest units to the millimeter length scale. Traditionally, this is achieved by a “top-down” approach that has miniaturized the originally 1 centimeter-sized transistor down to the 100 nm structures found on a Pentium ® chip [2].

Macromolecules make up the fabric of life. Without the protein machinery and DNA/RNA as information carriers, no cell would be able to complete its life cycle and to remain in a non-equilibrium thermodynamical state. Looking beyond the chemical structure of proteins and DNA, it becomes clear that their intricate interactions with other macromolecules form the core of their functionality. In DNA, this is evident in the formation of the double helix through H-bonding, whereas in proteins, numerous examples of functional macromolecular assemblies exist. A particularly impressive example of such a macromolecular assembly is the photosystem I, which is a trimeric complex forming a large disc (Figure 2.1). However, each complex is an assembly of a dozen proteins, bringing together and precisely positioning hundreds of co-factors (chlorophyll). An equally impressive example of cellular machinery based on macromolecules is the ribosome complex, where RNA read-out and protein synthesis take place (Figure 2.1). It is beyond the scope of this chapter to discuss the exact mechanisms of assembly and function, but these examples do illustrate the tremendous potential of polymers in nanotechnology, if, at least, we learn to harness such systems in man-made devices. A first step towards harnessing the power of biological ‘machines’ has been demonstrated by the seminal work of Montemagno and co-workers. By engineering a biomolecular nanomotor F1—adenosine triphosphate synthase (F1-ATPase) and integrating this biomolecule into an inorganic nanoscale system, they demonstrated the feasibility of building a nanomechanical device powered by a biomolecular motor.

The field of nanotechnology has made tremendous progress in the past decades, ranging from the experimental manipulations of single atoms and single molecules to the synthesis and possible applications of carbon nanotubes and semiconductor nanowires. This remarkable research trend is driven partly by the human being's curiosities of exploring the ultimate small matter and partly by the microelectronics industry's need to go beyond the traditional photolithography-based top-down fabrication limitations. As the enormous literature has shown, nanometer scale device structures provide suitable testbeds for the investigations of novel physics in a new regime, especially at the quantum level, such as single electron tunneling or quantum confinement effect., On the other hand, as the semiconductor device feature size keeps decreasing, the traditional top-down microfabrications will soon enter the nanometer range and further continuous downscaling will become scientifically and economically challenging. This motivates researchers around the world to find alternate ways to meet the future increasing computing demands.

Self-assembly has become a promising option for the construction of molecular nanoscale devices. Well-defined nanostructures, also termed “supramolecular aggregates”, are formed by self-assembly of a limited number of well-defined building blocks with strong affinity for each other. They are formed via reversible noncovalent interactions such as hydrophobic and electrostatic effect, π—π stacking, hydrogen bonds and/or metal coordination. These noncovalent systems, generally highly dynamic on the human time scale, are distinctly different from the non-reversible covalent molecules, and they offer some advantages. The advantage of noncovalent synthesis is that noncovalent bonds are formed spontaneously and reversibly under conditions of thermodynamic equilibrium, with the possibility of error correction and without undesired side products. Furthermore, it does not require harsh chemical reagents or conditions. For instance, we have developed the self-assembly of nanosized molecular structures as large as ~5.5 x 3.1 x 2.7 nm, via molecular recognition between complementary hydrogen-bonding building blocks, that are otherwise inaccessible via covalent synthesis. These hydrogen-bonded aggregates form spontaneously under thermodynamically controlled conditions, which give these nanostructures their ability to “proofread” and correct mistakes.

When Moore's Law hits the solid-state fabrication “brick wall,” researchers in the field of molecular electronics want to be there to pick up the pieces, using self-assembly as one of the tools. Of course, Gordon Moore, one of the founders of Intel, did not actually posit a Law, he made a prediction that the number of components “crammed” onto integrated circuits would double every year. This prediction was later modified to a doubling every 18 months, and has held true long past the 1975 end date Moore originally used, an accuracy that convinced industry pundits to refer to his prediction as a Law.

Since their initial fabrication two decades ago by McConnell and coworkers, fluid supported phospholipid bilayers (SLBs) have played a key role in the development of nanoscale assemblies of biological materials on artificial supports. The reason for this is quite straightforward. SLBs can serve as biomimetics for chemical and biological processes which occur in cell membranes. A thin aqueous layer (approximately 1 nm thick) is trapped between the bilayer and the underlying support (Figure 6.1). Thiswater layer acts as a lubricant allowing both leaflets of the bilayer to remain fluid. Consequently, planar supported membranes retain many of the physical properties of free vesicles or even native cell surfaces when the appropriate recognition components are present. Specifically, SLBs are capable of undergoing lateral rearrangements to accommodate binding by aqueous proteins, viruses, toxins, and even cells. As substrate supported entities, they are convenient to study by a host of interface-sensitive techniques and are far less fragile than either unsupported membranes or full-blown cellular systems.

Nature often uses the self-assembly of amphiphilic building blocks as a tool for the structuring of matter. The most representative example of the functionality that can be achieved through the interplay between different, structurally simple, monomeric units is the cell membrane. In this natural supramolecular structure, the organization is achieved by the self-assembly of different types of individual functional molecules (phospholipids, glycolipids, glycoproteins, membrane spanning peptide helices, the cytoskeleton, etc). The resulting cell membrane combines functionality, compartmentalization, order and mobility, characteristics all essential for life. The realization of the importance of self-assembly in Nature has led scientists to extensively explore its basic principles in the last decades. The designed self-assembly of individual molecules has led to macromolecular structures of one, two or three-dimensional nature. These supramolecular structures can contain between 10 and 10 molecules and thus resemble synthetic and biological polymers in molecular mass. As G. M. Whitesides stated; “.” Though significant progress has been achieved, it still is a challenge to try to understand in full detail the principles that govern the self-organization of individual molecules leading to the formation of nanometer sized assemblies, and furthermore to be able to manipulate these nanometer scale functionalities and enhance their properties.

Colloids are small particles with at least one of their dimensions in the range of a few nanometers to one micrometer, where Brownian motion plays a critical role. They are analogous to giant molecules in some respects, and behave in fair agreement with statistical mechanics. Since the pioneering work by Faraday and Graham more than 140 years ago, colloids has become a subject of great importance to many fields that include chemistry, biology, materials science, condensed matter physics, applied optics, and fluid dynamics. The enormous impact of colloids can also be appreciated by their extensive use in a variety of commercial products such as foods, drinks, inks, paints, toners, coatings, papers, cosmetics, photographic films, and magnetic recording media.

“Nanostructured materials” are those having properties defined by features smaller than 100 nm. This class of materials is interesting for the reasons: i) They include materials, since a broad range of properties—from fracture strength to electrical conductivity—depend on nanometer-scale features. ii) They may offer properties: The conductivity and stiffness of buckytubes, and the broad range of fluorescent emission of CdSe quantum dots are examples. iii) They can mix classical and quantum behaviors. iv) They offer a bridge between classical and biological branches of materials science. v) They suggest approaches to “materials-by-design”. Nanomaterials can, in principle, be made using both top-down and bottom-up techniques. Self-assembly bridges these two techniques and allows materials to be designed with hierarchical order and complexity that mimics those seen in biological systems. Self-assembly of nanostructured materials holds promise as a low-cost, high-yield technique with a wide range of scientific and technological applications.