Page 120 - Nanotechnology an introduction

Criteria applied in interactive evolutionary computation are not usually specifiable—if they were, there would be no need to use IEC. It is especially
important when considering the esthetic features of a design.

An important criterion applicable to nanobiotechnological devices in medicine (Section 4.2) is resistance to opsonization. Opsonization is that
process whereby a foreign object inside a living organism becomes coated with proteins that signal to the immune system that the object must be
eliminated. Thus, a key parameter for drug delivery nanoparticles is how long they can circulate in the body. Nanoparticles circulating in a complex
fluid such as blood typically attract a protein corona around them, a complex multicomponent composite whose structure is essentially dynamic,
continuously varying. Particularly if protein denaturation takes place (Section 4.1.4 and Figure 4.5) the particle is likely to be recognized as foreign.

10.9. Scaleout
Traditional process design begins with small-scale laboratory experiments, continues with a pilot scale fabrication, in some factories fortunate to
have the capacity it may then be possible to run an experiment on the existing manufacturing plant, before finally a dedicated production unit is
designed and put into operation. At each transition to the next scale up, it is scarcely to be expected that control parameters can simply be
multiplied by the length or volume (etc.) scaling factor. In complicated processes, the behavior may even change qualitatively. Scaleup is therefore
very problematical.
On the other hand, a process implemented at the nanoscale requires only to be multiplied (this is called scaleout). Scaling performance up to the
level of human utility is simply a matter of massive parallelization. For example, nanoreactors synthesizing a medicinal drug simply need to work in
parallel to generate enough of the compound for a therapeutically useful dose. This introduces new problems of connexions and synchronization,
but whereas practically each scaleup problem needs to be solved de novo in an ad hoc fashion, once the general principles of scaleout are
established they are universally valid.
With information processors, the problem is the user interface: a visual display screen must be large enough to show a useful amount of legible
information, a keyboard for entering instructions and data must be large enough for human fingers, and so forth—these kinds of problems have
already been addressed with microsystems technology (e.g., for reading information stored on microfilm).
10.10. Standardization
Standardization is the key to any viable system. The richness and robustness of bacterial life is due to a high degree of standardization of their
genomes, such that genetic material can be readily exchanged between them. Engineers require a standard vocabulary in order to work together
and create standard specifications for interchangeable components of industrial systems.

Nanotechnology is no exception. Even though the nanotechnology industry is still in its infancy, the International Organization for Standardization
(ISO) and the International Electrotechnical Commission (IEC) are jointly preparing a multipart Technical Specification (as a precursor to an
International Standard) for the vocabulary of nanotechnology (ISO/TS 80004), some parts of which have already been published. These specify
terms and definitions relating to nano-objects and nanostructured materials, carbon nano-objects, the nano/bio interface, nanometrology,
nanomanufacturing processes, and so forth.

10.11. Creative Design
New ways of connecting known components together could yield new functions. The Nanotechnology Age may usher in a new era of creative leaps,
reminiscent of the great Victorian era of engineering. When Richard Trevithick designed and built, in 1803, the first railway locomotive in the world
(a replica of which is displayed in the hall of Telford Central Station in the UK) he had to solve design problems that no one had ever encountered
before—and many of his solutions have persisted in essence to this day. The same applies to the bridges of totally new structure conceived by
Brunel, the Stephenson brothers, and others. Will we now embark on a new panopticon of creative design comparable to the immense creative
energy of that earlier era?
One needs to examine how the novel possibilities of nanotechnology can be fully exploited from the design viewpoint. While structure is familiarly a
fixed given that determines function, living cells present hints of function retroacting on structure. Can this principle be extended to the inanimate
world? Can the “structure” intermediate be short-circuited in nanotechnology?; that is, can we determine the components needed to assemble a
device with specified functional properties directly, without considering what structure it should have? This may be especially relevant when
considering structures that are not static, but act dynamically (e.g., an enzyme, cf. Section 11.3). The methods described in Section 10.7 are
especially appropriate to such an approach.
10.12. Produceability

Any viable design must be associated with a practicable route to fabrication. The evolutionary design process described in Section 10.7 could
readily be extended to encompass manufacturability. A database of existing manufacturing systems could be a starting point for evaluating the
fitness of a design, but the design process could be extended to encompass the production system itself.
It is a corollary of the principles enunciated in Section 10.4 that very small features (with characteristic dimensions of a few nm) will have fluctuations
of the order of tens of percent in atom numbers (and, hence, in any properties dependant on those numbers) if mass-produced by a top-down
approach. In the clearly foreseeable future the only way to counter such manufacturing variability is to harness self-limiting phenomena such as
described in Section 8.2.9; in the longer term eutectic environments mimicking what nature achieves in, for example, protein synthesis should have
the capability of providing reliable production.
Similar considerations apply to marketability. Existing domain knowledge might best be incorporated into the evaluation step interactively, using
commercial marketing experts, but the design process could itself devise appropriate and novel approaches to creating a market for the product.

10.13. Summary
Systems and nanosystems are defined. Nanotechnology implies many departures from traditional engineering practice. Regarding choice of
materials, one should ultimately no longer be constrained to merely select suitable materials; rather, materials with exactly the required properties
can be specified and produced. Computation is much more intimately connected with nanotechnology than with larger scale technologies, because
explicit and reliable simulation of complete systems is often possible. To cope with vastification, evolutionary computation offers a solution, vastly