3.3 Nanoscience and Nanotechnology
Current knowledge of science at the nanometre scale is derived from many disciplines, originating with the atomic and molecular concepts in chemistry and physics, and then incorporating molecular life sciences, medicine and engineering. The observation and understanding of atomic and molecular behaviour from first principles was followed by the increasing ability to control and selectively modify properties of ever smaller pieces of matter in a functional way. Early examples here are the discoveries in self assembly (Bain et al 1989) which culminated in current synthetic and supra-molecular chemistry (Lehn 1988, Gomez –Lopez et al 1996), the increasing knowledge about life’s replication processes and the co-evolution of physical (Perutz et al 1960, Aue et al 1976, Wuthrich 1995) and chemical methodologies. These have resulted in the portfolio of current molecular life sciences such as molecular motors and other functional entities (Mavroidis et al 2004, Clark et al 2004), including biomolecular and medical engineering and the emerging area of systems biology. On the other hand, man made micro and nanoscale sensing devices originate from other domains in microscopy and device engineering but relate to biomedical applications (Ziegler 2004, Emerich and Thanos 2003).
The deviation of surface and interface properties from the bulk properties of larger amounts of materials led to the sometimes unexpected significance of surface effects, including catalytic activity and wetting behaviour in material composed of nanosized entities, such as nanoparticles, composites and colloids (Kamat 2002, Schwerdtfeger 2003). Quantum mechanical principles manifest themselves in the properties of surfaces of clusters of very small particles, especially those of the order of 1000 atoms or molecules and less. Composite materials (Komarneni 1992, Schmidt 2000, Hadjipanayis 1999), with increasingly smaller characteristic sizes of the domains or phases, allowed for the design of materials with new and optimised physical and / or chemical properties. In electronic engineering, the miniaturization of devices has progressed well into the nanometre range with gate oxides in devices being routinely 25 nm thick. The recently increased public awareness of nanoscience is closely related to the availability of first real space images of atomic and molecular processes at surfaces through the invention of Scanning Probe Microscopies (Binnig and Rohrer 1985).
With the continuous development of nanotechnology, the possibility for the bottom-up production of nanoscale materials may result in some kind of self assembly of structures similar to the self assembly of phospholipid bilayers that resembles cellular membranes.
On the basis of current knowledge however, the spontaneous formation of artificial living systems through self assembly and related processes, suggested by some prominent commentators, is considered highly improbable. The combination of self replication with self perpetuation in an engineered nanosystem is extremely difficult to realize on the basis of current scientific knowledge.
3.3.2 Examples of Engineered Nanostructures and Materials and Their Applications
There are several areas of science and technology in which nanoscale structures are under active development or already in practical use.
In materials science, nanocomposites with nanoscale dispersed phases and nanocrystalline materials in which the very fine grain size affords quite different mechanical properties to conventional microstructures are already in use. In surface science and surface engineering, nanotopographies offer substantially different properties related to adhesion, tribology, optics and electronic behaviour. Supramolecular chemistry and catalysis have led to novel surface and size dependent chemistry, such as enantioselective catalysis at surfaces. In biological sciences, fundamental understanding of molecular motors and molecular functional entities on the nanometre scale has been responsible for advances in drug design and targeting. Nanoscale functionalised entities and devices are in development for analytical and instrumental applications in biology and medicine, including tissue engineering and imaging.
The application areas in which these advances in nanoscience are making their biggest impact include electronic, electro-optic and optical devices. The transition from semiconductor (conventional and organic) technology to nanoscale devices has anticipated improved properties and resolution, e.g. fluorescence labelling, scanning probe microscopy and confocal microscopy. Data storage devices based on nanostructures provide smaller, faster, and lower consumption systems.
In medicine, greater understanding of the origin of diseases on the nanometre scale is being derived, and drug delivery through functionalised nanostructures may result in improved pharmacokinetic and targeting properties.
A wide variety of functional nanoscale materials and functional nanoscale surfaces are in use in consumer products, including cosmetics and sunscreens, fibres and textiles, dyes, fillers, paints, emulsions and colloids.