Page 133 - Nanotechnology an introduction

needs to be stored, hence the interest in simultaneous conversion and storage (e.g., Figure 7.24). Undoubtedly natural photosynthesis is only
possible through an extremely exact arrangement of atoms within the photosystems working within plant cells, and the more precisely artificial light
harvesters can be assembled, the more successful they are likely to be.
Fuel Cells
Although the scientific basis of this technology, whereby fuel is converted to electricity directly, was established over 150 years ago by Christian
Schünbein, it has been very slow to become established. As with photovoltaic cells, the main primary obstacle is the high cost of fabrication.
Nanotechnology is expected to contribute through miniaturization of all components (especially reducing the thickness of the various laminar parts),
simultaneously reducing inefficiencies and costs, and through realizing better catalysts for oxygen reduction and fuel oxidation. A particular priority
is developing fuel cells able to use feedstocks other than hydrogen.
Energy Storage
The primary means of storing energy is as fuel, but unless photoelectrochemical cells generating fuel from sunlight receive renewed impetus,
renewable sources will mainly produce electricity and except for some special cases at least some of the electricity will have to be stored to enable
the supply to match demand. Supercapacitors based on carbon nanotubes have attracted interest, but the impact of nanotechnology is likely to be
small since using ordinary carbon black has already enabled over 90% of the theoretical maximum charge storage capacity to be achieved, at
much lower cost. In any case, the classic photoelectrochemical process generates hydrogen (from water), the storage of which is problematical.
Through the design and fabrication of rational storage matrix materials, nanotechnology should be able to contribute to effective storage, although
whether this will tip the balance in favor of the hydrogen economy is still questionable.
Energy Efficiency
This heading comprises a very heterogeneous collection of technical impacts. Nanostructured coatings with very low coefficients of friction and
extremely good wear resistance will find application in all moving machinery, hence improving its efficiency and reducing the energy required to
achieve a given result. Examples include electricity-generating wind turbines and electric motors. For all applications where collateral heat
production is not required, nanotechnology-enabled light-emitting diodes can replace incandescent filaments. They can achieve a similar luminous
output for much less power than incandescent lamps. The heat produced by the latter may be of value in a domestic context (e.g., contributing to
space heating in winter) that is simply wasted in the case of outdoor street lighting (although the esthetic effect is very agreeable). Note that,
however, the actual operational efficiency of a device in a given functional context typically represents only a fraction of the overall effectiveness in
achieving the intended function. For example, if the intended function of street lighting is to reduce road accidents, there is probably an ergonomic
limit to the number of lamps per unit length of street above which energy saving becomes insignificant. Although data are hard to come by, it seems
that few amenities have been properly analyzed in this manner. It may well be that a 50% reduction in the number of lamps could be effected without
diminution of the functional effect. Such a reduction would be equivalent to a really significant technological advance in the device technology.
Miniaturizing computer chips diminishes the heat dissipated per floating point operation (but, at present, not by as much as the increased number
of floating point operations per unit area enabled by the miniaturization, cf. Section 7.5). Devices in which bits are represented as electron spins
rather than as electron charges will dissipate practically no heat.

Resource Extraction
Current technologies used to extract metal from ores use vastly more energy than is theoretically required. Nanotechnology can be brought to bear
on this problem in many different ways. Biomimicry seems a very attractive route to explore especially since living organisms are extremely good at
extracting very dilute raw materials from their environment, operating at room temperature and, seemingly, close to the thermodynamic limit.
Localized Manufacture
Possibly the greatest ultimate contribution of nanotechnology, once the stage of the personal nanofactory has been reached, to energy
conservation will be through the great diminution of the need to transport raw materials and finished products around the world. The amount of
energy currently consumed by transport in one form or another is something between 30 and 70% of total energy consumption. A reduction by an
order of magnitude is perhaps achievable.
The above are realizable to a degree using already-available nanotechnology—the main issue is whether costs are low enough to make them
economically viable.

12.3.3. Health

Impacts can be summarized under the following headings:
Diagnosis
Many diagnostic technologies should benefit from the contributions of nanotechnology. Superior contrast agents based on nanoparticles have
already demonstrated enhancement of tissue imaging. Nanoscale biochemical sensors offer potentially superior performance and less
invasiveness, to the extent that implanted devices may be able to continuously sense physiological parameters. More powerful computers able to
apply pattern recognition techniques to identify pathological conditions from a multiplicity of indicators provide an indirect diagnostic benefit.
Therapy
The most prominent development has been the creation of functionally rich nanostructured drug packaging, enabling the more effective delivery of
awkward molecules to their targets. Implants with controlled drug-eluting capability enabled by nanostructured coatings have also been
demonstrated. Indirect therapeutic impacts include more powerful computers accelerating the numerical simulation stage of drug discovery, and
nano-enabled microreactors facilitating the affordable production of customized medicines, which depends at least in part on the availability of
individual patient genomes.
Surgery
Miniaturized devices are making surgery less and less invasive. The basic surgical tools are unlikely to be miniaturized below the microscale,
however, but their deployment may be enhanced by nanoscale features such as ultralow friction coatings and built-in sensors for in situ monitoring