nanotechnology - Fundamental concepts, Current research, Speculation, Societal implications, Further reading

The science of construction in which dimensions of the components are less than 100 nanometres (nm; 10^?9 of a metre), this is c.100 000 times thinner than a human hair. The term was introduced by Nomo Taniguchi in 1974 to refer to mechanical machining methods. Top-down nanotechnology concentrates on manufacturing on this very small scale. Techniques such as photolithography are used to make transistors for integrated circuits; the smaller the transistor, and the closer together they are packed, the higher the processing power of the chip. An Intel Pentium chip has about 1·5 million transistors. A specialized Dynamic Random Access (DRAM) chip carries 64 million transistors. Bottom-up nanotechnology builds with individual atoms. A Scanning Tunnelling Microscope (STM) is used to manipulate and arrange individual atoms exactly as required. A recent development has been the Nanomanipulator, which senses the electric fields of the atoms; this uses 3-D computer graphics and virtual reality technology to allow the scientists to see and feel the atoms as they move them. In 1985, naturally occurring crystals called fullerenes were discovered. One type is the Buckminsterfullerene (nicknamed a Buckyball), a hollow carbon ball which is so strong that it can be used as tiny ball bearings. Rolling up a sheet of carbon atoms produces a tube which is only a nanometre wide. If metals are sucked up the tiny tube and the straw then dissolved, the result is a nanowire which can be used in microelectric circuits. The application of nanotechnology may result in revolutionary methods of atom-by-atom manufacturing and surgery on a cellular scale, as well as the creation of computers of great compactness and power.

Nanotechnology is a term describing a broad range of avenues of current scientific inquiry, all having in common a focus on understanding and controlling the structure of matter on a scale below 100 nanometers. Nanotechnology has as its goal the realization of novel materials and devices with features on the nanoscale, with active research proceeding into such varied aspects as their design, synthesis, characterization, and application.

Despite the apparent simplicity of this definition, nanotechnology actually encompasses a very diverse group of lines of inquiry, each taking different approaches and using different methods to progress towards different applications. Nanotechnology cuts across many disciplines, including colloid science, chemistry, physics, biology, and other scientific fields; Two main approaches are used in nanotechnology: one is a "bottom-up" approach where materials and devices are built from smaller (molecular) components which assemble themselves chemically using principles such as molecular recognition;

The impetus for nanotechnology has stemmed from a renewed interest in colloidal science, coupled with a new generation of analytical tools such as the atomic force microscope (AFM) and the scanning tunneling microscope (STM). Nanotechnology is also used as an umbrella term to describe emerging or novel technological developments associated with microscopic dimensions. Despite the great promise of numerous nanotechnologies such as quantum dots and nanotubes, real applications that have moved out of the lab and into the marketplace have mainly utilized the advantages of colloidal nanoparticles in bulk form, such as suntan lotion, cosmetics, protective coatings, and stain resistant textiles.

Fundamental concepts

Use of the term

Most broadly, nanotechnology includes the many techniques used to create structures at a size scale below 100 nanometers.

Nanotechnological techniques include those used for fabrication of nanowires, those used in semiconductor fabrication such as deep ultraviolet lithography, electron beam lithography, focused ion beam machining, nanoimprint lithography, atomic layer deposition, and molecular vapor deposition, and further including molecular self-assembly techniques such as those employing di-block copolymers. However, all of these techniques preceded the nanotech era, and are extensions in the development of scientific advancements rather than techniques which were devised with the sole purpose of creating nanotechnology or which were results of nanotechnology research.

Technologies currently branded with the term 'nano' are little related to and fall far short of the most ambitious and transformative technological goals of the sort in molecular manufacturing proposals, but the term still connotes such ideas.

The National Science Foundation (a major source of funding for nanotechnology in the United States) funded researcher David Berube to study the field of nanotechnology. His findings are published in the monograph “Nano-Hype: The Truth Behind the Nanotechnology Buzz.” This published study (with a foreword by Mihail Roco, head of the NNI) concludes that much of what is sold as “nanotechnology” is in fact a recasting of straightforward materials science, which is leading to a “nanotech industry built solely on selling nanotubes, nanowires, and the like” which will “end up with a few suppliers selling low margin products in huge volumes."

Effects of the nanoscale

A unique aspect of nanotechnology is the vastly increased ratio of surface area to volume present in many nanoscale materials, which opens new possibilities in surface-based science, such as catalysis.

Nanotechnology can be thought of as extensions of traditional disciplines towards the explicit consideration of these properties. Additionally, traditional disciplines can be re-interpreted as specific applications of nanotechnology. Broadly speaking, nanotechnology is the synthesis and application of ideas from science and engineering towards the understanding and production of novel materials and devices.

General fields involved with proper characterization of these systems include physics, chemistry, and biology, as well as mechanical and electrical engineering. However, due to the inter- and multidisciplinary nature of nanotechnology, subdisciplines such as physical chemistry, materials science, or biomedical engineering are considered significant or essential components of nanotechnology. The manufacture of polymers based on molecular structure, or the design of computer chip layouts based on surface science are examples of nanotechnology in modern use. Colloidal suspensions also play an essential role in nanotechnology.

Materials reduced to the nanoscale can suddenly show very different properties compared to what they exhibit on a macroscale, enabling unique applications. Much of the fascination with nanotechnology stems from these unique quantum and surface phenomena that matter exhibits at the nanoscale.

Tools and techniques

Nanoscience and nanotechnology only became possible in the 1910's with the development of the first tools to measure and make nanostructures.

The atomic force microscope (AFM) and the Scanning Tunneling Microscope (STM) are two early versions of scanning probes that launched nanotechnology.

The tip of scanning probes can also be used to manipulate nanostructures (a process called positional assembly).

Lithography is a top-down fabrication technique where a bulk material is reduced in size to nanoscale pattern.

In contrast, bottom-up techniques build or grow larger structures atom by atom or molecule by molecule.

Newer techniques such as Dual Polarisation Interferometry are enabling scientists to measure quantitatively the molecular interactions that take place at the nano-scale.

Potential difficulties

One very basic problem facing nanotechnology, a problem which is widely ignored, is the issue of scale.

For example let's see what happens when we try to scale down a typical machine, say a drill.

Now let's try to scale it down to smaller dimensions, still very far from nanosize.

This basic problem is why while we have super-miniature electronic integrated circuits, the same technology can't be used to make miniature and functioning mechanical devices-- there's just too much friction at small scales.

It's not only friction that is a major problem, but also surface tension.

These scaling issues have to be kept in mind while evaluating any kind of nanotechnology.

Another one of the problems facing nanotechnology concerns how to assemble atoms and molecules into smart materials and working devices.

Current research

As nanotechnology is a very broad term, there are many disparate but sometimes overlapping subfields that could fall under its umbrella. The following avenues of research could be considered subfields of nanotechnology:

This list is incomplete; Nanomaterials includes subfields which develop or study materials having unique properties arising from their nanoscale dimensions: Colloid science has given rise to many materials which may be useful in nanotechnology, such as carbon nanotubes and other fullerenes, and various nanoparticles and nanorods. most present commerical applications of nanotechnology are of this flavor. Top-down approaches seek to create smaller devices by using larger ones to direct their assembly: Many technologies descended from conventional solid-state silicon methods for fabricating microprocessors are now capable of creating featres smaller than 100 nm, falling under the definition of nanotechnology.

Note that these categories are fairly nebulous and a single subfield may overlap many of them, especially as the field of nanotechnology continues to mature.

See also List of nanotechnology applications.

Speculation

Molecular manufacturing

Advanced nanotechnology, sometimes called molecular manufacturing, is a term given to the concept of engineered nanosystems (nanoscale machines) operating on the molecular scale. By the countless examples found in biology it is currently known that billions of years of evolutionary feedback can produce sophisticated, stochastically optimized biological machines, and it is hoped that developments in nanotechnology will make possible their construction by some shorter means, perhaps using biomimetic principles. However, K Eric Drexler and other researchers have proposed that advanced nanotechnology, although perhaps initially implemented by biomimetic means, ultimately could be based on mechanical engineering principles (see also mechanosynthesis)

When the term "nanotechnology" was independently coined and popularized by Eric Drexler, who at the time was unaware of Taniguchi's usage, it referred to a future manufacturing technology based on molecular machine systems. The premise was that molecular-scale biological analogies of traditional machine components demonstrated that molecular machines were possible, and that a manufacturing technology based on the mechanical functionality of these components (such as gears, bearings, motors, and structural members) would enable programmable, positional assembly to atomic specification (see the original reference PNAS-1981).

Another view, put forth by Carlo Montemagno, is that future nanosystems will be hybrids of silicon technology and biological molecular machines, and his group's research is directed toward this end.

The seminal experiment proving that positional molecular assembly is possible was performed by Ho and Lee at Cornell University in 1999.

Though biology clearly demonstrates that molecular machine systems are possible, non-biological molecular machines are today only in their infancy.

Manufacturing in the context of productive nanosystems is not related to, and should be clearly distinguished from, the conventional technologies used to manufacture nanomaterials such as carbon nanotubes and nanoparticles.

There exists the potential to design and fabricate artificial structures analogous to natural cells and even organisms.

Possible approaches to nanodevice design

Some nanodevices self-assemble. Shanefield, Kluwer Academic Publ., Boston.)

Societal implications

Potential risks of nanotechnology can broadly be grouped into three areas:

the risk to health and environment from nanoparticles and nanomaterials;

In August 2005, a task force consisting of 50+ international experts from various fields was organized by the Center for Responsible Nanotechnology to study the societal implications of molecular nanotechnology .

Determining a set of pathways for the development of molecular nanotechnology is now an objective of a broadly based technology roadmap project led by Battelle (the manager of several U.S. National Laboratories) and the Foresight Institute.

Risks from nanoparticles

The mere presence of nanomaterials (materials that contain nanoparticles) is not in itself a threat.

In addressing the health and environmental impact of nanomaterials we need to differentiate two types of nanostructures: (1) Nanocomposites, nanostructured surfaces and nanocomponents (electronic, optical, sensors etc.), where nanoscale particles are incorporated into a substance, material or device (“fixed” nano-particles); These free nanoparticles could be nanoscale species of elements, or simple compounds, but also complex compounds where for instance a nanoparticle of a particular element is coated with another substance (“coated” nanoparticle or “core-shell” nanoparticle).

There seems to be consensus that, although one should be aware of materials containing fixed nanoparticles, the immediate concern is with free nanoparticles.

Because nanoparticles are very different from their everyday counterparts, their adverse effects cannot be derived from the known toxicity of the macro-sized material.

To complicate things further, in talking about nanoparticles it is important that a powder or liquid containing nanoparticles is almost never monodisperse, but will contain a range of particle sizes.

The lethal dose over six months for lab rats, of different kinds of nanoparticles are often characterized by a Skov Kjaer index, named after the scientist Kasper Skov Kjaer.

Health issues

There are several potential entry routes for nanoparticles into the body.

How these nanoparticles behave inside the organism is one of the big issues that needs to be resolved. Apart from what happens if non-degradable or slowly degradable nanoparticles accumulate in organs, another concern is their potential interaction with biological processes inside the body: because of their large surface, nanoparticles on exposure to tissue and fluids will immediately absorb onto their surface some of the macromolecules they encounter.

Environmental issues

Not enough data exists to know for sure if nanoparticles could have undesirable effects on the environment.

Health and environmental issues combine in the workplace of companies engaged in producing or using nanomaterials and in the laboratories engaged in nanoscience and nanotechnology research.

To properly assess the health hazards of engineered nanoparticles the whole life cycle of these particles needs to be evaluated, including their fabrication, storage and distribution, application and potential abuse, and disposal.

Regarding the risks from molecular manufacturing, an often cited worst-case scenario is "grey goo", a hypothetical substance into which the surface of the earth might be transformed by self-replicating nanobots running amok. Here, the malignant substance is not nanobots but rather self-replicating organisms engineered through nanotechnology.

Possible military applications

Societal risks from the use of nanotechnology have also been raised. On the instrumental level, these include the possibility of military applications of nanotechnology (for instance, as in implants and other means for soldier enhancement like those being developed at the Institute for Soldier Nanotechnologies at MIT ) as well as enhanced surveillance capabilities through nano-sensors.

Potential benefits and risks for developing countries

Nanotechnologies may provide new solutions for the millions of people in developing countries who lack access to basic services, such as safe water, reliable energy, health care, and education. The 2004 UN Task Force on Science, Technology and Innovation noted that some of the advantages of nanotechnology include production using little labor, land, or maintenance, high productivity, low cost, and modest requirements for materials and energy.

Many developing countries, for example Costa Rica, Chile, Bangladesh, Thailand, and Malaysia, are investing considerable resources in research and development of nanotechnologies.

Potential opportunities of nanotechnologies to help address critical international development priorities include improved water purification systems, energy systems, medicine and pharmaceuticals, food production and nutrition, and information and communications technologies. Nanotechnologies are already incorporated in products that are on the market. Other nanotechnologies are still in the research phase, while others are concepts that are years or decades away from development.

Applying nanotechnologies in developing countries raises similar questions about the environmental, health, and societal risks described in the previous section. Additional challenges have been raised regarding the linkages between nanotechnology and development.

Protection of the environment, human health and worker safety in developing countries often suffers from a combination of factors that can include but are not limited to lack of robust environmental, human health, and worker safety regulations;

Very little is known about the risks and broader impacts of nanotechnology. At a time of great uncertainty over the impacts of nanotechnology it will be challenging for governments, companies, civil society organizations, and the general public in developing countries, as in developed countries, to make decisions about the governance of nanotechnology.

Companies, and to a lesser extent governments and universities, are receiving patents on nanotechnology. The rapid increase in patenting of nanotechnology is illustrated by the fact that in the US, there were 500 nanotechnology patent applications in 1998 and 1,300 in 2000.

There is a clear link between commodities and poverty. Many applications of nanotechnology are being developed that could impact global demand for specific commodities. Other nanotechnology applications may result in increases in demand for certain commodities.

In 2003, Meridian Institute began the Global Dialogue on Nanotechnology and the Poor: Opportunities and Risks (GDNP) to raise awareness of the opportunities and risks of nanotechnology for developing countries, close the gaps within and between sectors of society to catalyze actions that address specific opportunities and risks of nanotechnology for developing countries, and identify ways that science and technology can play an appropriate role in the development process. The GDNP has released several publicly accessible papers on nanotechnology and development, including "Nanotechnology and the Poor: Opportunities and Risks - Closing the Gaps Within and Between Sectors of Society"; "Nanotechnology, Water, and Development";

Intellectual property issues

On the structural level, critics of nanotechnology point to a new world of ownership and corporate control opened up by nanotechnology. The claim is that, just as biotechnology's ability to manipulate genes went hand in hand with the patenting of life, so too nanotechnology's ability to manipulate molecules has led to the patenting of matter. For example, two corporations, NEC and IBM, hold the basic patents on carbon nanotubes, one of the current cornerstones of nanotechnology.

A need for regulation?

Regulatory bodies such as the Environmental Protection Agency and the Food and Drug Administration in the U.S. or the Health & The Material Safety Data Sheet that must be issued for certain materials often does not differentiate between bulk and nanoscale size of the material in question.

Studies of the health impact of airborne particles are the closest thing we have to a tool for assessing potential health risks from free nanoparticles.

Looking at all available data, it must be concluded that current risk assessment methodologies are not suited to the hazards associated with nanoparticles;

Regulatory bodies in the U.S. as well as in the EU have concluded that nanoparticles form the potential for an entirely new risk and that it is necessary to carry out an extensive analysis of the risk.