Difference between revisions of "Nanotechnology" - New World Encyclopedia

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[[Image:Nanogearandbug.jpg|thumb|250px|right|A [[mite]] next to a [[gear]] set produced using [[MEMS]], the precursor to nanotechnology. Courtesy Sandia National Laboratories, SUMMiTTM Technologies, www.mems.sandia.gov]]
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'''Nanotechnology''' comprises [[technology|technological]] developments on the [[nanometer]] scale, usually 0.1 to 100 nm. (One nanometer equals one thousandth of a [[micrometre]] or one millionth of a [[millimetre]].) The term has sometimes been applied to [[microscope|microscopic]] technology. This article discusses nanotechnology, nanoscience, and [[molecular nanotechnology]].
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[[Image:C60a.png|thumb|right|200px|Buckminsterfullerene C<sub>60</sub>, also known as the buckyball, is the simplest of the [[Allotropes of carbon|carbon structures]] known as [[fullerene]]s. Members of the fullerene family are a major subject of research falling under the nanotechnology umbrella.]]
  
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==Intro==
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'''Nanotechnology''' is a field of applied science and technology covering a broad range of topics. The main unifying theme is the control of matter on a scale smaller than 1 [[micro]]meter, normally between 1-100 nanometers, as well as the fabrication of devices on this same length scale. It is a highly [[Interdisciplinary|multidisciplinary]] field, drawing from fields such as [[colloid]]al science, [[Semiconductor device|device physics]], and [[supramolecular chemistry]]. Much speculation exists as to what new science and technology might result from these lines of research. Some view nanotechnology as a marketing term that describes pre-existing lines of research applied to the sub-micron size scale.
  
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===Definition===
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Despite the apparent simplicity of this definition, nanotechnology actually encompasses diverse lines of inquiry. Nanotechnology cuts across many disciplines, including [[colloid]]al science, [[chemistry]], [[applied physics]], [[materials science]], and even [[Mechanical engineering|mechanical]] and [[electrical engineering]]. It could variously be seen as an extension of existing sciences into the nanoscale, or as a recasting of existing sciences using a newer, more modern term. Two main approaches are used in nanotechnology: one is a "bottom-up" approach where materials and devices are built from [[Molecule|molecular]] components which [[self-assembly|assemble themselves]] chemically using principles of [[molecular recognition]]; the other being a "top-down" approach where nano-objects are constructed from larger entities without atomic-level control.
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{{toc}}
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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). Combined with refined processes such as [[electron beam lithography]] and [[molecular beam epitaxy]], these instruments allow the deliberate manipulation of nanostructures, and in turn led to the observation of novel phenomena. 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. 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 clothing.
  
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Nanotechnology is any technology which exploits phenomena and structures that can only occur at the nanometer scale, which is the scale of several atoms and small molecules.  The [[United States]]' [[National Nanotechnology Initiative]] [http://www.nano.gov/html/facts/whatIsNano.html website] defines it as follows: "Nanotechnology is the understanding and control of matter at dimensions of roughly 1 to 100 nanometers, where unique phenomena enable novel applications." Such phenomena include [[quantum confinement]]—which can result in different electromagnetic and optical properties of a material between [[nanoparticles]] and the bulk material; the [[Gibbs-Thomson effect]]—which is the lowering of the melting point of a material when it is nanometers in size; and such structures including [[carbon nanotubes]]. Nanoscience and nanotechnology are an extension of the field of [[materials science]], and materials science departments at universities around the world in conjunction with [[physics]], [[mechanical engineering]], [[bioengineering]], and [[chemical engineering]] departments are leading the breakthroughs in nanotechnology.
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{{Nanotech}}
  
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The related term '''nanoscience''' is used to describe the [[interdisciplinary]] fields of science devoted to the study of nanoscale phenomena employed in nanotechnology. This is the world of atoms, molecules, [[macromolecule]]s, [[quantum dot]]s, and macromolecular assemblies, and is dominated by surface effects such as [[Van der Waals force]] attraction, [[hydrogen bond]]ing, electronic charge, [[ionic bond]]ing, [[covalent bond]]ing, [[hydrophobe|hydrophobicity]], [[hydrophile|hydrophilicity]], and [[quantum tunneling|quantum mechanical tunneling]], to the virtual exclusion of [[macroscopic|macro-scale]] effects such as [[turbulence]] and [[inertia]]. For example, the vastly increased ratio of surface area to volume opens new possibilities in surface-based science, such as [[catalysis]].
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== History ==
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Nanoscience and nanotechnology only became possible in the 1910s with the development of the first tools to measure and make nanostructures. But the actual development started with the discovery of electrons and neutrons which showed scientists that matter can really exist on a much smaller scale than what we normally think of as small, and/or what they thought was possible at the time. It was at this time when curiosity for nanostructures had originated.
  
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===History of Use===
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The [[atomic force microscope]] (AFM) and the [[Scanning Tunneling Microscope]] (STM) are two early versions of scanning probes that launched nanotechnology. There are other types of [[scanning probe microscopy]], all flowing from the ideas of the scanning [[confocal microscope]] developed by [[Marvin Minsky]] in 1961 and the [[scanning acoustic microscope]] (SAM) developed by [[Calvin Quate]] and coworkers in the 1970s, that made it possible to see structures at the nanoscale. The tip of a scanning probe can also be used to manipulate nanostructures (a process called positional assembly). Feature-oriented scanning-positioning methodology suggested by Rostislav Lapshin appears to be a promising way to implement these nanomanipulations in automatic mode. However, this is still a slow process because of low scanning velocity of the microscope. Various techniques of nanolithography such as dip pen nanolithography, electron beam lithography or nanoimprint lithography were also developed. Lithography is a top-down fabrication technique where a bulk material is reduced in size to nanoscale pattern.
  
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The first mention of some of the distinguishing concepts in nanotechnology (but predating use of that name) was in "[[There's Plenty of Room at the Bottom]]", a talk given by physicist [[Richard Feynman]] at an [[American Physical Society]] meeting at [[Caltech]] on [[December 29]], [[1959]]. Feynman described a process by which the ability to manipulate individual atoms and molecules might be developed, using one set of precise tools to build and operate another proportionally smaller set, so on down to the needed scale. In the course of this, he noted, scaling issues would arise from the changing magnitude of various physical phenomena: gravity would become less important, surface tension and Van der Waals attraction would become more important, etc. This basic idea appears feasible, and [[exponential assembly]] enhances it with [[parallelism]] to produce a useful quantity of end products.
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The first distinguishing concepts in nanotechnology (but predating use of that name) was in "[[There's Plenty of Room at the Bottom]]," a talk given by physicist [[Richard Feynman]] at an [[American Physical Society]] meeting at [[Caltech]] on December 29, 1959 <ref>Alan Chodos, (ed.) [http://www.aps.org/publications/apsnews/200012/history.cfm ''American Physics Society'']"December 29, 1959: Feynman's Classic CalTech Lecture." Retrieved June 28, 2007.</ref>. Feynman described a process by which the ability to manipulate individual atoms and molecules might be developed, using one set of precise tools to build and operate another proportionally smaller set, so on down to the needed scale. In the course of this, he noted, scaling issues would arise from the changing magnitude of various physical phenomena: gravity would become less important, surface tension and [[Van der Waals force|Van der Waals attraction]] would become more important. This basic idea appears feasible, and [[exponential assembly]] enhances it with [[parallelism]] to produce a useful quantity of end products.
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[[Image:Allotropes of Carbon.png|thumb|200px|left| Eight allotropes of Carbon]]
  
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The term "nanotechnology" was defined by [[Tokyo Science University]] professor [[Norio Taniguchi]] in a [[1974]] paper (N. Taniguchi, "On the Basic Concept of 'Nano-Technology'," Proc. Intl. Conf. Prod. Eng. Tokyo, Part II, Japan Society of Precision Engineering, 1974.) as follows: "'Nano-technology' mainly consists of the processing of, separation, consolidation, and deformation of materials by one atom or one molecule." In the 1980s the basic idea of this definition was explored in much more depth by [[Eric Drexler| Dr. Eric Drexler]], who promoted the technological significance of nano-scale phenomena and devices through speeches and the books [[ Engines of Creation: The Coming Era of Nanotechnology]] and ''Nanosystems: Molecular Machinery, Manufacturing, and Computation,'' (ISBN 0-471-57518-6), and so the term acquired its current sense.
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The term "nanotechnology" was defined by [[Tokyo Science University]] Professor [[Norio Taniguchi]] in a 1974 paper <ref>N. Taniguchi. "On the Basic Concept of 'Nano-Technology'." ''Proc. Intl. Conf. Prod. Eng.'' Part II, (1974) (Tokyo: Japan Society of Precision Engineering)</ref> as follows: "'Nano-technology' mainly consists of the processing of, separation, consolidation, and deformation of materials by one atom or by one molecule." In the 1980s the basic idea of this definition was explored in much more depth by [[Eric Drexler|Dr. K. Eric Drexler]], who promoted the technological significance of nano-scale phenomena and devices through speeches and the book ''Engines of Creation: The Coming Era of Nanotechnology''<ref>K. Eric Drexler. 1992. ''Nanosystems: molecular machinery, manufacturing, and computation.'' (New York: Wiley. ISBN 0471575186) Nanosystems: Molecular Machinery, Manufacturing, and Computation.</ref>, and so the term acquired its current sense.
  
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More broadly, nanotechnology includes the many techniques used to create structures at a size scale below 100 nm, including those used for fabrication of [[nanowire]]s, those used in [[semiconductor fabrication]] such as deep ultraviolet [[photolithography|lithography]], [[electron beam lithography]], focused [[ion beam]] machining,[[Nanoimprint Lithography]] [[chemical vapor deposition|atomic layer deposition, and molecular vapor deposition]], and further including [[self-assembly|molecular self-assembly]] techniques such as those employing di-block [[copolymer]]s. It should be noted, however, that all of these techniques preceeded 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.
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Nanotechnology and nanoscience got started in the early 1980s with two major developments; the birth of [[Cluster (physics)|cluster]] science and the invention of the [[scanning tunneling microscope]] (STM). This development led to the discovery of [[fullerenes]] in 1986 and [[carbon nanotubes]] a few years later. In another development, the synthesis and properties of semiconductor [[nanocrystal]]s was studied. This led to a fast increasing number of metal oxide nanoparticles of [[quantum dots]]. The [[atomic force microscope]] was invented five years after the STM was invented. The AFM uses atomic force to "see" the atoms.
  
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The term nanotechnology is sometimes conflated with the more specific [[molecular nanotechnology]] (also known as "MNT"), a proposed form of advanced nanotechnology based on [http://www.e-drexler.com/ productive nanosystems]. Molecular nanotechnology would fabricate precise structures using [[mechanosynthesis]] to perform [http://wise-nano.org/ molecular manufacturing]. Molecular nanotechnology, though not yet extant, is expected to have a [http://www.crnano.org/overview.htm great impact] on society if realized. In August 2005, a [http://www.crnano.org/CTF.htm 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.
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== Fundamental concepts ==
  
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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. Thus there may be a danger that a nano [[Bubble_(economics)|bubble]] will form from the use of the term by scientists and entrepreneurs to garner funding, regardless of (and perhaps despite a lack of) interest in the transformative possibilities of more ambitious and far-sighted work. The diversion of support based on the promises of proposals like molecular manufacturing to more mundane projects also risks creating a perhaps unjustifiedly cynical impression of the most ambitious goals: an investor intrigued by [[molecular manufacturing]] who invests in 'nano' only to find typical [[materials science]] advances result might conclude that the whole idea is [[Technology_hype|hype]], unable to appreciate the [[bait-and-switch]] made possible by the vagueness of the term. On the other hand, some have argued that the publicity and competence in related areas generated by supporting such 'soft nano' projects is valuable, even if indirect, progress towards nanotechnology's most ambitious goals.
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One nanometer (nm) is one billionth, or 10<sup>-9</sup> of a meter. For comparison, typical carbon-carbon [[bond length]]s, or the spacing between these atoms in a molecule, are in the range .12-.15 nm, and a [[DNA]] double-helix has a diameter around 2 nm. On the other hand, the smallest [[Cell (biology)|cellular]] lifeforms, the bacteria of the genus [[Mycoplasma]], are around 200 nm in length.
  
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==New materials, devices, technologies==
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=== Larger to smaller: a materials perspective ===
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<<CLEAN UP THIS SECTION>>
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[[image:Atomic_resolution_Au100.JPG‎|left|250px|thumb|Image of [[Surface reconstruction|reconstruction]] on a clean [[Gold|Au]]([[Miller index|100]]) surface, as visualized using [[scanning tunneling microscopy]]. The individual [[atom]]s composing the surface are visible.]]
  
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As manufacturing technology becomes more sophisticated it naturally enters the realm of what is arbitrarily labeled nanotechnology. Nanotechnology is based on the fact that the [[properties]] of materials become markedly different when their size approaches that of a few hundreds or tens of atoms. [[Nanoparticle]]s (nanometer sized clusters of atoms), for example, have proved useful in [[catalysis]]. A material that is catalytically inactive on the [[Macroscopic|macroscale]] can behave as a very efficient catalyst when in the form of nanoparticles. For this and other reasons, if [[nanorobot|nanobots]] are ever created they will not simply be scaled down versions of contemporary robots (an image popularised by [[Eric Drexler]]). The different physics at these scales means that man-made nanodevices will probably bear much stronger resemblance to nature's nanodevices: made from [[protein]]s, [[DNA]] and [[biological membrane|membranes]], much like viruses. This idea is explored by [[Richard A. L. Jones]] in his book ''Soft Machines: Nanotechnology and Life'' (ISBN 0-19-852855-8).
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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]]. A number of physical phenomena become noticeably pronounced as the size of the system decreases. These include [[statistical mechanics|statistical mechanical]] effects, as well as [[quantum mechanics|quantum mechanical]] effects, for example the “[[quantum]] size effect” where the electronic properties of solids are altered with great reductions in particle size. This effect does not come into play by going from macro to micro dimensions. However, it becomes dominant when the nanometer size range is reached. Additionally, a number of [[physical properties]] change when compared to macroscopic systems. One example is the increase in surface area to volume of materials.
  
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One fundamental characteristic of nanotechnology is that nanodevices self-assemble. That is, they build themselves from the bottom up. [[Scanning probe microscopy]] is an important technique both for characterization and synthesis of nanomaterials. [[Atomic force microscope]]s and [[scanning tunneling microscope]]s can be used to look at surfaces and to move atoms around. By designing different tips for these microscopes, they can be used for carving out structures on surfaces and to help guide self-assembling structures. Atoms can be moved around on a surface with scanning probe microscopy techniques, but it is cumbersome, expensive and very time-consuming, and for these reasons it is quite simply not feasible to construct nanoscaled devices atom by atom. You don't want to assemble a billion transistors into a microchip by taking an hour to place each transistor, but these techniques can be used for things like helping to guide self-assembling systems.
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Materials reduced to the nanoscale can suddenly show very different properties compared to what they exhibit on a macroscale, enabling unique applications. For instance, opaque substances become transparent (copper); inert materials become catalysts (platinum); stable materials turn combustible (aluminum); solids turn into liquids at room temperature (gold); insulators become conductors (silicon). A material such as [[gold]], which is chemically inert at normal scales, can serve as a potent chemical [[catalyst]] at nanoscales. Much of the fascination with nanotechnology stems from these unique quantum and surface phenomena that matter exhibits at the nanoscale.
  
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One of the problems facing nanotechnology is how to assemble atoms and molecules into smart materials and working devices. [[Supramolecular chemistry]] is here a very important tool. Supramolecular chemistry is the chemistry beyond the molecule, and molecules are being designed to [[self-assembly|self-assemble]] into larger structures. In this case, biology is a place to find inspiration: cells and their pieces are made from self-assembling [[biopolymer]]s such as [[protein]]s and protein complexes. One of the things being explored is synthesis of [[organic compound|organic molecules]] by adding them to the ends of [[complementary DNA]] [[DNA#Overview of molecular structure|strands]] such as ----A and ----B, with molecules A and B attached to the end; when these are put together, the complementary DNA strands hydrogen bonds into a [[double helix]], ====AB, and the DNA molecule can be removed to isolate the product AB.
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=== Simple to complex: a molecular perspective ===
  
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Natural or man-made particles or artifacts often have qualities and capabilities quite different from their macroscopic counterparts. [[Gold]], for example, which is chemically inert at normal scales, can serve as a potent chemical [[catalyst]] at nanoscales.
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Modern [[Chemical synthesis|synthetic chemistry]] has reached the point where it is possible to prepare small [[molecule]]s to almost any structure. These methods are used today to produce a wide variety of useful chemicals such as [[drug|pharmaceuticals]] or commercial [[polymer]]s. This ability raises the question of extending this kind of control to the next-larger level, seeking methods to assemble these single molecules into [[Supramolecular assembly|supramolecular assemblies]] consisting of many molecules arranged in a well defined manner.
  
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"Nanosize" powder particles (a few nanometres in diameter, also called nano-particles) are potentially important in [[ceramic]]s, [[powder metallurgy]], the achievement of uniform nanoporosity, and similar applications. The strong tendency of small particles to form clumps ("agglomerates") is a serious technological problem that impedes such applications. However, a few dispersants such as ammonium citrate (aqueous) and imidazoline or [[oleyl alcohol]] (nonaqueous) are promising additives for deagglomeration. (Those materials are discussed in "Organic Additives And Ceramic Processing," by D. J. Shanefield, Kluwer Academic Publ., Boston.)
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These approaches utilize the concepts of [[molecular self-assembly]] and/or [[supramolecular chemistry]] to automatically arrange themselves into some useful conformation through a [[bottom-up]] approach. The concept of [[molecular recognition]] is especially important: molecules can be designed so that a specific conformation or arrangement is favored. The Watson-Crick [[Base pair|basepairing]] rules are a direct result of this, as is the specificity of an [[enzyme]] being targeted to a single [[Substrate (biochemistry)|substrate]], or the specific [[Protein folding|folding of the protein]] itself. Thus, two or more components can be designed to be complementary and mutually attractive so that they make a more complex and useful whole.
  
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In October 2004, researchers at the [[University of Manchester]] succeeded in forming a small piece of material only 1 atom thick called [[graphene]].[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15499015] [[Robert Freitas]] has suggested that graphene might be used as a [[deposition (chemistry)|deposition]] surface for a [[diamondoid]] [[mechanosynthesis]] tool.[http://www.molecularassembler.com/Papers/PathDiamMolMfg.htm]
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Such bottom-up approaches should, broadly speaking, be able to produce devices in parallel and much cheaper than top-down methods, but could potentially be overwhelmed as the size and complexity of the desired assembly increases. Most useful structures require complex and thermodynamically unlikely arrangements of atoms. Nevertheless, there are many examples of self-assembly based on molecular recognition in [[biology]], most notably [[Base pair|Watson-Crick basepairing]] and [[enzyme]]-[[Substrate (biochemistry)|substrate]] interactions. The challenge for nanotechnology is whether these principles can be used to engineer novel constructs in addition to natural ones.
  
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As of [[August 23]] 2004, [[Stanford University]] has been able to construct a transistor from single-walled carbon nanotubes and organic molecules. These single-walled carbon nanotubes are basically a rolled up sheet of carbon atoms. They have accomplished creating this transistor making it two nanometers wide and able to maintain current three nanometers in length. To create this transistor they cut metallic nanotubes in order to form electrodes, and afterwards placed one or two organic materials to form a [[semiconductor|semiconducting]] channel between the [[electrode]]s. It is projected that this new achievement will be available in different applications in two to five years.
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=== Molecular nanotechnology ===
  
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[http://news.com.com/Barrett+No+end+in+sight+for+Moores+Law/2100-1006_3-5594779.html News.com] reported on [[March 1st]] [[2005]] that [[Intel]] is preparing to introduce [[central processing unit|processors]] with features measuring 65 nanometers. The company’s current engineers believe that 5 nanometer processes are actually proving themselves to be more and more feasible. The company showed pictures of these transistor prototypes measuring 65, 45, 32, and 22 nanometers. However, the company spoke about how their expectations for the future are for new processors featuring 15,10, 7, and 5 nanometers.
 
  
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Currently the prototypes use [[CMOS]] (complementary metal-oxide semiconductors); however, according to Intel smaller scales will rely on quantum dots, polymer layers, and nanotube technology.
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Molecular nanotechnology, sometimes called molecular manufacturing, is a term given to the concept of engineered nanosystems (nanoscale machines) operating on the molecular scale. It is especially associated with the concept of a [[molecular assembler]], a machine that can produce a desired structure or device atom-by-atom using the principles of [[mechanosynthesis]]. 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.
  
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[http://www.PhysOrg.com PhysOrg.com] writes about the use of [[plasmons]] in the world. Plasmons are waves of electrons traveling along the surface of metals. They have the same frequency and [[electromagnetic field]] as light; however, the sub-wavelength size allows them to use less space. These plasmons act like light waves in glass on metal, allowing engineers to use any of the same tricks such as multiplexing, or sending multiple waves. With the use of plasmons information can be transferred through chips at an incredible speed; however, these plasmons do have drawbacks. For instance, the distance plasmons travel before dying out depends on the metal, and even currently they can travel several millimeters, while chips are typically about a centimeter across from each other. In addition, the best metal currently available for plasmons to travel farther is aluminum. However, most industries that manufacture chips use copper over aluminum since it is a better [[electrical conduction|electrical conductor]]. Furthermore, the [[computer cooling|issue of heat]] will have to be looked upon. The use of plasmons will definitely generate heat but the amount is currently unknown.
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When the term "nanotechnology" was independently coined and popularized by [[Eric Drexler]] (who at the time was unaware of an [[History of nanotechnology|earlier usage]] by [[Norio Taniguchi]]) 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 molecular machines were possible: by the countless examples found in biology, it is known that billions of years of evolutionary feedback can produce sophisticated, [[stochastic]]ally optimized biological machines. It is hoped that developments in nanotechnology will make possible their construction by some other means, perhaps using [[biomimetic]] principles. However, Drexler and other researchers have proposed that advanced nanotechnology, although perhaps initially implemented by biomimetic means, ultimately could be based on mechanical engineering principles, namely, a manufacturing technology based on the mechanical functionality of these components (such as gears, bearings, motors, and structural members) that would enable programmable, positional assembly to atomic specification PNAS-1981. The physics and engineering performance of exemplar designs were analyzed in Drexler's book <ref>Ibid. [http://www.e-drexler.com/d/06/00/Nanosystems/toc.html Nanosystems: Molecular Machinery, Manufacturing, and Computation]</ref>. But Drexler's analysis is very qualitative and does not address very pressing issues, such as the "fat fingers" and "Sticky fingers" problems, which are problems related to the difficulty in handling and assembling on the nanoscale. In general it is very difficult to assemble devices on the atomic scale, as all one has to position atoms are other atoms of comparable size and stickiness.
  
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The further developments in the field of nanotechnology focuses on the [[oscillation]] of a nanomachine for [[telecommunication]]. The article states that in Boston an antenna-like sliver of [[silicon]] one-tenth the width of a human hair oscillated in a lab in a [[Boston University]] basement. This team led by Professor Pritiraj Mohanty developed the sliver of silicon. Since the technology functions at the speeds of [[gigahertz]] this could help make communication devices smaller and exchange information at gigahertz speeds. This nanomachine is comprised of 50 billion atoms and is able to oscillate at 1.49 billion times per second. The antenna moves over a distance of one-tenth of a [[picometer]].
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Another view, put forth by Carlo Montemagno <ref> [http://www.cnsi.ucla.edu/institution/personnel?personnel%5fid=105488 Carlo Montemagno], UCLA People: "Carlo Montemagno." Retrieved November 30, 2007. </ref> is that future nanosystems will be hybrids of silicon technology and biological molecular machines. Yet another view, put forward by the late [[Richard Smalley]], is that mechanosynthesis is impossible due to the difficulties in mechanically manipulating individual molecules. This led to an exchange of letters <ref>[http://pubs.acs.org/cen/coverstory/8148/8148counterpoint.html ''American Chemical and Engineering News''] Retrieved June 28, 2007.</ref> in the [[American Chemical Society|ACS]] publication [[Chemical & Engineering News]] in 2003.
  
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==Advanced nanotechnology==
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Though biology clearly demonstrates that molecular machine systems are possible, non-biological molecular machines are today only in their infancy. Leaders in research on non-biological molecular machines are Dr. Alex Zettl and his colleagues at Lawrence Berkeley Laboratories and UC Berkeley. They have constructed at least three distinct molecular devices whose motion is controlled from the desktop with changing voltage: a nanotube [[nanomotor]], a molecular actuator <ref>B. C. Regan, et al. ''Nano Letters'' 5(9)(2005):1730-1733.[http://www.physics.berkeley.edu/research/zettl/pdf/312.NanoLett5regan.pdf ''Nano Crystal Powered Motor''] Retrieved June 28, 2007.</ref>, and a nanoelectromechanical relaxation oscillator <ref>B. C. Regan, et al. "Surface-tesion-driven nanoelectromechanical relaxation" ''Applied Physics Letters'' 86 (2005):123119.(UC Berkeley). </ref> An experiment indicating that positional molecular assembly is possible was performed by Ho and Lee at [[Cornell University]] in 1999. They used a scanning tunneling microscope to move an individual carbon monoxide molecule (CO) to an individual iron atom (Fe) sitting on a flat silver crystal, and chemically bound the CO to the Fe by applying a voltage.
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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, [[stochastic]]ally 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 [http://www.crnano.org/developing.htm other researchers] have proposed that advanced nanotechnology, although perhaps initially implemented by biomimetic means, ultimately could be based on mechanical engineering principles.
 
  
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Sandia National Labs currently produces "Self Assembling Nano Inks" which can be used in standard inkjet printers.
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== Current research ==
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As the inks dry they assemble into arrays, cavities, q-dots etc.
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[[Image:Rotaxane.jpg|thumbnail|250px|Graphical representation of a [[rotaxane]], useful as a molecular switch.]]
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[[Image:Achermann7RED.jpg|200px|thumb|right|This device transfers energy from nano-thin layers of [[quantum well]]s to [[nanocrystal]]s above them, causing the nanocrystals to emit visible light <ref> [http://www.sandia.gov/news-center/news-releases/2004/micro-nano/well.html Wireless nanocrystals efficiently radiate visible light] Sandina National Labs. Retrieved June 28, 2007.</ref>]]
  
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A company called nanoink builds a "rapid prototyping" nano structure fabication machine which picks up atom chains and deposits them in a precise manner per the build file.
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Nanotechnology is a very broad term, there are many different but sometimes overlapping subfields that could fall under its umbrella. The following avenues of research could be considered subfields of nanotechnology. Note that these categories are not concrete and a single subfield may overlap many of them, especially as the field of nanotechnology continues to mature.
  
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Determining a set of pathways for the development of [[molecular nanotechnology]] is now an objective of a broadly based [[technology roadmaps|technology roadmap]] project [http://physorg.com/news4656.html] led by [[Battelle Memorial Institute | Battelle]] (the manager of several U.S. National Laboratories) and the [[Foresight Institute]]. That roadmap should be completed by late 2006. In August 2005, a [http://www.crnano.org/CTF.htm task force] consisting of 50+ international experts from various fields was organized by the [[Center for Responsible Nanotechnology]] to study the societal implications of advanced nanotechnology.
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=== Nanomaterials ===
  
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==Interdisciplinary ensemble==
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This includes subfields which develop or study materials having unique properties arising from their nanoscale dimensions.
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A definitive feature of nanotechnology is that it constitutes an interdisciplinary ensemble of several fields of the natural sciences that are, in and of themselves, actually highly specialized. Thus, physics plays an important role—alone in the construction of the microscope used to investigate such phenomena but above all in the laws of [[quantum mechanics]]
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* [[Colloid]] science has given rise to many materials which may be useful in nanotechnology, such as [[carbon nanotube]]s and other [[fullerene]]s, and various nanoparticles and nanorods.
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* Nanoscale materials can also be used for bulk applications; most present commercial applications of nanotechnology are of this flavor.
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* Progress has been made in using these materials for medical applications.
  
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==Potential risks==
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=== Bottom-up approaches ===
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===Goo===
 
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An often cited worst-case for everyone [[scenario planning|scenario]] is "[[grey goo]]", a hypothetical substance into which the surface objects of the earth might be transformed by self-replicating [[nanobots]] running amok, a process which has been termed [[global ecophagy]]. Defenders point out that smaller objects are more susceptible to damage from [[background radiation|radiation]] and heat (due to greater surface area-to-volume ratios): nanomachines would quickly fail when exposed to harsh climates. This argument depends on the speed of which such nanomachines might be able to reproduce.
 
  
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Recently, [http://www.crnano.org/PR-IOP.htm new analysis] has shown that this "grey goo" danger is less likely than originally thought.  [[K. Eric Drexler]] considers an accidental "[[grey goo]]" scenario extremely unlikely and says so in later editions of ''Engines of Creation''.  The "[[grey goo]]" scenario begs the Tree Sap Answer: what chances exist that one's car could spontaneously mutate into a wild car, run off-road and live in the forest off tree sap? However, other long-term major risks to society and the environment have been identified.
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These seek to arrange smaller components into more complex assemblies.
 +
* DNA Nanotechnology utilizes the specificity of [[Base pair|Watson-Crick basepairing]] to construct well-defined structures out of [[DNA]] and other [[nucleic acid]]s.
 +
* More generally, molecular self-assembly seeks to use concepts of supramolecular chemistry, and molecular recognition in particular, to cause single-molecule components to automatically arrange themselves into some useful conformation.
  
−
A variant on this is "[[Green Goo]]", a scenario in which [[nanobiotechnology]] creates a self-replicating nano machine which consumes all organic particles, living or dead, creating a slime -like non-living organic mass.
+
=== Top-down approaches ===
  
−
Both of these would, however, be limited by the same mechanism limiting all life forms (who generally already behave this way): available energy.
+
These seek to create smaller devices by using larger ones to direct their assembly.
 +
* Many technologies descended from conventional [[Semiconductor fabrication|solid-state silicon methods]] for fabricating [[microprocessor]]s are now capable of creating features smaller than 100 nm, falling under the definition of nanotechnology. [[Giant magnetoresistance]]-based [[hard disk drive]]s already on the market fit this description, as do [[atomic layer deposition]] (ALD) techniques.
 +
* Solid-state techniques can also be used to create devices known as [[nanoelectromechanical systems]] or NEMS, which are related to [[microelectromechanical systems]] (MEMS).
 +
* [[Atomic force microscope]] tips can be used as a nanoscale "write head" to deposit a chemical on a surface in a desired pattern in a process called [[dip pen nanolithography]]. This fits into the larger subfield of [[nanolithography]].
  
−
===Poison/Toxicity===
+
=== Functional approaches ===
−
For the near-term, critics of nanotechnology point to the potential toxicity of new classes of nanosubstances that could adversely affect the stability of cell membranes or disturb the immune system when inhaled or digested. Objective risk assessment can profit from the bulk of experience with long-known microscopic materials like carbon soot or asbestos fibres.
 
  
−
There is a possibility that nanoparticles in drinking water could be dangerous to humans and/or other animals. Colon cells exposed to nano titanium dioxide particles have been found to decay at a quicker than normal rate. Titanium dioxide nanoparticles are often used in sunscreens, as they make them transparent, compared to bigger titanium dioxide particles, which make the sunscreen appear white.
+
These seek to develop components of a desired functionality without regard to how they might be assembled.
 +
* [[Molecular electronics]] seeks to develop molecules with useful electronic properties. These could then be used as single-molecule components in a nanoelectronic device.  
 +
* Synthetic chemical methods can also be used to create [[synthetic molecular motors]], such as in a so-called nanocar.
  
−
===Weapons===
+
=== Speculative ===
−
The weaponization of nanotechnology is a potential application. While advanced nanomaterials obviously have applications for improving existing weapons and military hardware through novel properties (such as improved strength to weight ratios or modified reflectivity to EM radiation for stealth applications), and molecular electronics could be used to build ruggedized computer systems for missiles, there is no obvious way for nanotechnology in any of its practical forms nowadays and into the foreseeable future to be weaponized beyond what is already possible with other technologies such as genetic engineering. While conceivably we could design nanomachines which attacked biological systems or the components of vehicles (i.e. a nanomachine which consumed the rubber in tires would quickly disable many vehicles), such designs are a far off concept.  In terms of efficacy, they might be compared to weapon concepts such as genetically engineered bacteria or viruses, which are similar in intended and practical function and still generally are unattractive tactical weapons, though their terrorism applications are clear.
 
  
−
Nanotechnology could be used to create highly undetectable or concealable surveillance devices - molecular sized microphones, cameras, and homing beacons are well within the realms of possibility.  The societal impact of such devices would depend on many factors, including who has access to them, how well they work, and how they are used.
+
These subfields seek to [[Futures studies|anticipate]] what inventions nanotechnology might yield, or attempt to propose an agenda along which inquiry might progress. These often take a big-picture view of nanotechnology, with more emphasis on its [[Implications of nanotechnology|societal implications]] than the details of how such inventions could actually be created.
 +
* [[Molecular nanotechnology]] is a proposed approach which involves manipulating single molecules in finely controlled, deterministic ways. This is more theoretical than the other subfields and is beyond current capabilities.
 +
* [[Nanorobotics]] centers on self-sufficient machines of some functionality operating at the nanoscale. There are hopes for applying nanorobots in medicine <ref>Z. Ghalanbor, S.A. Marashi, and B. Ranjbar. 2005. "Nanotechnology helps medicine: nanoscale swimmers and their future applications." ''Medical Hypotheses'' 65 (1): 198-199.</ref> <ref>T. Kubik, K. Bogunia-Kubik, and M. Sugisaka. 2005. "Nanotechnology on duty in medical applications." ''Current Pharmaceutical Biotechnology'' 6 (1): 17-33.</ref> <ref>A. Cavalcanti, and R.A. Freitas, Jr. 2005. "Nanorobotics control design: a collective behavior approach for medicine." ''IEEE Transactions on Nanobioscience'' 4 (2): 133-140.</ref>, while it might not be easy to do such a thing because of several drawbacks of such devices  
 +
<ref>R.C. Shetty. 2005. "Potential pitfalls of nanotechnology in its applications to medicine: immune incompatibility of nanodevices." ''Medical Hypotheses'' 65 (5): 998-999.</ref> Nevertheless, progress on innovative materials and methodologies has been demonstrated with some patents granted about new nanomanufacturing devices for future commercial applications, which also progressively helps in the development towards nanorobots with the use of embedded nanobioelectronics concept.
  
 +
* [[Programmable matter]] based on [[artificial atom]]s seeks to design materials whose properties can be easily and reversibly externally controlled.
 +
* Due to the popularity and media exposure of the term nanotechnology, the words [[pico]]technology and [[femto]]technology have been coined in analogy to it, although these are only used rarely and informally.
  
−
== See also ==
+
== Tools and techniques ==
−
* [[List of nanotechnology topics]]
+
 
 +
[[Image:AFMsetup.jpg|thumb|left|300px|Typical [[Atomic force microscope|AFM]] setup. A [[Microfabrication|microfabricated]] [[cantilever]] with a sharp tip is deflected by features on a sample surface, much like in a [[phonograph]] but on a much smaller scale. A [[laser]] beam reflects off the backside of the cantilever into a set of [[photodetector]]s, allowing the deflection to be measured and assembled into an image of the surface.]] Another technique uses SPT™s (surface patterning tool) as the molecular “ink cartridge.” Each SPT is a microcantilever-based micro-fluidic handling device. SPTs contain either a single microcantilever print head or multiple microcantilevers for simultaneous printing of multiple molecular species. The integrated microfluidic network  transports fluid samples from reservoirs located on the SPT through microchannels to the distal end of the cantilever. Thus SPTs can be used to print materials that include biological samples such as proteins, DNA, RNA, and whole viruses, as well as non-biological samples such as chemical solutions, colloids and particle suspensions. SPTs are most commonly used with molecular printers.
 +
 
 +
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 and which were results of nanotechnology research.
 +
 
 +
The top-down approach anticipates nanodevices that must be built piece by piece in stages, much as manufactured items are currently made. [[Scanning probe microscopy]] is an important technique both for characterization and synthesis of nanomaterials. [[Atomic force microscope]]s and [[scanning tunneling microscope]]s can be used to look at surfaces and to move atoms around. By designing different tips for these microscopes, they can be used for carving out structures on surfaces and to help guide self-assembling structures. By using, for example, feature-oriented scanning-positioning approach, atoms can be moved around on a surface with scanning probe microscopy techniques. At present, it is expensive and time-consuming for mass production but very suitable for laboratory experimentation.
 +
 
 +
In contrast, bottom-up techniques build or grow larger structures atom by atom or molecule by molecule. These techniques include [[chemical synthesis]], [[self-assembly]] and positional assembly. Another variation of the bottom-up approach is [[molecular beam epitaxy]] or MBE. Researchers at [[Bell Telephone Laboratories]] like John R. Arthur, Alfred Y. Cho, and Art C. Gossard developed and implemented MBE as a research tool in the late 1960s and 1970s. Samples made by MBE were key to the discovery of the fractional quantum Hall effect for which the 1998 [[Nobel Prize in Physics]] was awarded. MBE allows scientists to lay down atomically-precise layers of atoms and, in the process, build up complex structures. Important for research on semiconductors, MBE is also widely used to make samples and devices for the newly emerging field of [[spintronics]].
 +
 
 +
Newer techniques such as Dual Polarization Interferometry are enabling scientists to measure quantitatively the molecular interactions that take place at the nano-scale.
 +
 
 +
== Applications ==
 +
 
 +
Although there has been much hype about the potential applications of nanotechnology, most current commercialized applications are limited to the use of "first generation" passive nanomaterials. These include titanium dioxide nanoparticles in sunscreen, cosmetics and some food products; silver nanoparticles in food packaging, clothing, disinfectants and household appliances; zinc oxide nanoparticles in sunscreens and cosmetics, surface coatings, paints and outdoor furniture varnishes; and cerium oxide nanoparticles as a fuel catalyst.  The Woodrow Wilson Center for International Scholars' Project on Emerging Nanotechnologies hosts an inventory of consumer products which now contain nanomaterials<ref>[http://www.nanotechproject.org/44 ''A Nanotechnology Consumer Products Inventory'' ] Woodrow Wilson International Center for Scholars
 +
Retrieved June 29, 2007.</ref>
 +
 
 +
However further applications which require actual manipulation or arrangement of nanoscale components await further research. Though technologies currently branded with the term 'nano' are sometimes little related to and fall far short of the most ambitious and transformative technological goals of the sort in molecular manufacturing proposals, the term still connotes such ideas. Thus there may be a danger that a "nano bubble" will form, or is forming already, from the use of the term by scientists and entrepreneurs to garner funding, regardless of interest in the transformative possibilities of more ambitious and far-sighted work.
 +
 
 +
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.<ref>David M. Berube. 2006. ''Nano-hype: the truth behind the nanotechnology buzz.'' (Amherst, NY: Prometheus Books. ISBN 1591023513) </ref>" This published study 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."
 +
 
 +
== Implications ==
 +
 
 +
Due to the far-ranging claims that have been made about potential applications of nanotechnology, a number of concerns have been raised about what effects these will have on our society if realized, and what action if any is appropriate to mitigate these risks.  Short-term issues include the effects that widespread use of nanomaterials would have on human health and the environment.  Longer-term concerns center on the implications that new technologies will have for society at large, and whether these could possibly lead to either a post scarcity economy, or alternatively exacerbate the wealth gap between developed and developing nations.
  
−
=== Prominent individuals in nanotechnology ===
+
=== Health and environmental issues ===
−
* [[Richard Feynman]]
 
−
* [[Norio Taniguchi]]
 
−
* [[K. Eric Drexler]]
 
−
* [[Robert Freitas]]
 
−
* [[Ralph Merkle]]
 
−
* [[Sumio Iijima]]
 
−
* [[Richard Smalley]]
 
−
* [[Erwin Müller]]
 
−
* [[Gerd Binnig]]
 
−
* [[David Britz]]
 
−
* [[Heinrich Rohrer]]
 
−
* [[Raymond Kurzweil]]
 
−
* [[Paul Alivisatos]]
 
−
* [[Chris Phoenix]]
 
−
* [[Mike Treder]]
 
−
* [[Tim McKnight]]
 
−
* [[Phaedon Avouris]]
 
−
* [[James Fraser Stoddart]]
 
−
* [[Richard Colton]]
 
  
−
== External links ==
+
There is a growing body of scientific evidence which demonstrates the potential for some [[nanomaterials]] to be [[toxic]] to humans or the environment <ref>Peter HM Hoet, et al. "Nanoparticles – known and unknown health risks." ''Journal of Nanobiotechnology'' 2(2004):12 [http://www.jnanobiotechnology.com/content/2/1/12 Nanoparticles – known and unknown health risks]Review and Abstract. Retrieved June 28, 2007.</ref><ref> Gunter Oberdorster. "Nanotoxicology: An Emerging Discipline Evolving from Studies of Ultrafine Particles." [http://www.ehponline.org/members/2005/7339/7339.html Environmental Health Perspectives] 113 (7) (July 2005) Review and Abstract.  Retrieved June 28, 2007.</ref><ref>Günter Oberdörster, et al. [http://www.particleandfibretoxicology.com/content/2/1/8/ Particle and Fibre Toxicology] ''Particle and Fibre Toxicology'' Retrieved June 28, 2007. </ref>.
  
−
====Articles====
+
The smaller a [[Nanoparticle|particle]], the greater its surface area to volume ratio and the higher its chemical reactivity and biological activity. The greater chemical reactivity of nanomaterials results in increased production of [[reactive oxygen species]] (ROS), including [[free radical]]s. ROS production has been found in a diverse range of nanomaterials including carbon [[fullerene]]s, [[carbon nanotube]]s and nanoparticle metal oxides. ROS and free radical production is one of the primary mechanisms of [[Nanotoxicity|nanoparticle toxicity]]; it may result in oxidative stress, inflammation, and consequent damage to proteins, membranes and DNA <ref>A. Nel, T. Xia, L. Mưadler, and N. Li. 2006. "Toxic potential of materials at the nanolevel." ''Science'' 311(5761)(2006):622-627.</ref>.  
−
* [http://www.smalltimes.com/document_display.cfm?document_id=7161 Molecular Nanotechnology: Fully Loaded with Benefits and Risks], by Mike Treder, published 2004 in [http://www.wfs.org/futurist.htm ''The Futurist'']
 
−
* [http://www.nanoindian.com Nanotechnology in India] Nanotechnology Gateway of India
 
−
* [http://topics.developmentgateway.org/nanotechnology Nanotechnology for Development]
 
−
* [http://www.trnmag.com/Stories/2005/030905/Nanotubes_boost_molecular_devices_Brief_030905.html Stanford University transistors]
 
−
* [http://mprc.pku.edu.cn/courses/architecture/spring2005/20nmpressfoils.pdf Intel prototypes]
 
−
* [http://news.com.com/Barrett+No+end+in+sight+for+Moores+Law/2100-1006_3-5594779.html News.com, March 1 2005 "Barrett: No end in sight for Moore's Law"]
 
−
* [http://pubs.acs.org/cen/coverstory/8148/8148counterpoint.html Drexler and Smalley make the case for and against 'molecular assemblers']
 
−
* Margaret E. Kosal, [http://www.thebulletin.org/article.php?art_ofn=so04kosal "Is Small Scary?"], ''Bulletin of the Atomic Scientists'', September/October 2004.
 
−
* [http://www.isracast.com/tech_news/091205_tech.htm Nano armor - Protecting the soldiers of tomorrow] - An article from IsraCast
 
−
* [http://store.britannica.com/content/pdf/Nanotech.pdf "Nanotechnology"]. First two pages of article from the ''Encyclopaedia Britannica'' via the Encyclopaedia Britannica Store.
 
  
−
====Journals and News====
+
The extremely small size of nanomaterials also means that they are much more readily taken up by the human body than larger sized particles. Nanomaterials are able to cross biological membranes and access [[Cell (biology)|cells]], tissues and organs that larger-sized particles normally cannot. Nanomaterials can gain access to the blood stream following inhalation or ingestion . At least some nanomaterials can penetrate the skin; even larger microparticles may penetrate skin when it is flexed . Broken skin is an ineffective particle barrier, suggesting that acne, eczema, wounds or severe sunburn may enable skin uptake of nanomaterials more readily. Once in the blood stream, nanomaterials can be transported around the body and are taken up by organs and tissues including the brain, heart, liver, kidneys, spleen, bone marrow and nervous system. Nanomaterials have proved toxic to human tissue and cell cultures, resulting in increased oxidative stress, inflammatory [[cytokine]] production and [[Necrosis|cell death]] . Unlike larger particles, nanomaterials may be taken up by cell [[mitochondria]] and the [[cell nucleus]]. Studies demonstrate the potential for nanomaterials to cause [[DNA]] [[mutation]] and induce major structural damage to mitochondria, even resulting in cell death.  
−
* [http://www.nanowerk.com Nanowerk News] — news updated daily
 
−
* [http://www.nanodaddy.com Hot Research Articles in Nanotechnology]- Compiled by Nanotechnologists
 
−
* [http://nanonovus.com — daily weblog
 
−
*[http://CRNano.typepad.com Responsible Nanotechnology] - daily weblog
 
−
* [http://www.nanotechnology.com/blogs/blognano Darrell Brookstein of nanotechnology.com] - daily weblog
 
−
* [http://www.nanotechnology.com/blogs/steveedwards Steve Edwards of nanotechnology.com] - daily weblog
 
−
* [http://www.nanobound.com Nanobound Weblog] - daily weblog
 
−
* [http://www.azonano.com/Materials.asp?Letter=_ Nanotechnology and Nanomaterials A to Z]
 
−
* [http://www.whatsnextnetwork.com/technology/index.php?cat=65 Recent Developments In Nanotechnology]
 
−
* [http://www.iop.org/EJ/journal/0957-4484 Nanotechnology], electronic journal since [[1990]], available on web and CD-ROM.
 
−
* [http://pubs.acs.org/journals/nalefd/ Nano Letters], electronic journal published by American Chemical Society.
 
−
* [http://aspbs.com/jnn/ Journal of Nanoscience and Nanotechnology]
 
−
* [http://www.aspbs.com/ctn/ Journal of Computational and Theoretical Nanoscience]
 
−
* [http://nanotechwire.com/ Nanotechnology news and related research]
 
−
* [http://www.NTalert.com/ Nanotechnology news links - updated daily]
 
−
* [http://nanotech-now.com/ Nanotechnology basics, news, and general information]
 
−
* [http://www.smalltimes.com/ Small Times: News about MEMS, Nanotechnology and Microsystems]
 
−
* [http://nanotechweb.org nanotechweb.org: nanotechnology news, products, jobs, events and information]
 
  
−
====Laboratories====
+
Size is therefore a key factor in determining the potential toxicity of a particle. However it is not the only important factor. Other properties of nanomaterials that influence toxicity include: chemical composition, shape, surface structure, surface charge, aggregation and solubility, and the presence or absence of [[functional group]]s of other chemicals . The large number of variables influencing toxicity means that it is difficult to generalize about health risks associated with exposure to nanomaterials – each new nanomaterial must be assessed individually and all material properties must be taken into account.  
−
* [http://www.nint.ca/ Canada's Flagship Nanotechnology Institute]
 
−
* [http://www.nanofab.ualberta.ca/ University of Alberta's Nanofabrication Facility]
 
−
* [http://www.memsnet.org/ The MEMS and Nanotechnology Clearinghouse / The world's most popular portal for Nanotechnology information, jobs, and events]
 
−
* [http://www.london-nano.ucl.ac.uk/ The London Centre for Nanotechnology / A research centre jointly set up by University College London and Imperial College London]
 
−
* [http://www.cnsi.ucla.edu/ The California NanoSystems Institute]
 
−
* [http://www.mems-exchange.org/ The MEMS and Nanotechnology Exchange / A repository of Nanotechnology fabrication information]
 
−
* [http://smalley.rice.edu/ The Smalley Group / Carbon Nanotechnology Laboratory]
 
−
* [http://cben.rice.edu/ Center for Biological and Environmental Nanotechnology]
 
−
* [http://bios.ewi.utwente.nl Bios: The Lab-on-a-Chip Group, Universiteit Twente ]
 
−
* [http://www.cnm.utexas.edu/ Center for Nano & Molecular Science & Technology- CNM at UT Austin]
 
−
* [http://cnst.rice.edu/ Center for Nanoscale Science and Technology at Rice University]
 
−
* [http://biomems.uwaterloo.ca/ Advanced Micro/Nanodevices Lab at the University of Waterloo]
 
−
* [http://www.cns.cornell.edu/ Cornell University Center for Nanoscale Systems]
 
−
* [http://www.cnf.cornell.edu/ Cornell NanoScale Science & Technology Facility (CNF)]
 
−
* [http://www.mesaplus.utwente.nl/ MESA+ Institute for Nanotechnology - Universiteit Twente]
 
−
* [http://www.ns.tudelft.nl The Kavli Institute of Nanoscience Delft]
 
−
* [http://www.uta.edu/engineering/nano/ NanoFab Research and Teaching Facility at the University of Texas at Arlington]
 
−
* [http://www.nanotech.utdallas.edu/ NanoTech Institute at the University of Texas at Dallas]
 
−
* [http://unit.aist.go.jp/nanotech/index.html Nanotechnology Research Institute] - [[National Institute of Advanced Industrial Science and Technology]]
 
−
* [http://www.macdiarmid.ac.nz/ The MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand]
 
  
−
====Nanotechnology and Society====
+
In its seminal 2004 report<ref>[http://www.nanotec.org.uk/finalReport.htm ''Nanoscience and nanotechnologies: opportunities and uncertainties''] The Royal Society Retrieved June 29, 2007.</ref>, the United Kingdom's Royal Society recommended that nanomaterials be regulated as new chemicals, that research laboratories and factories treat nanomaterials "as if they were [[Hazardous material|hazardous]]," that release of nanomaterials into the environment be avoided as far as possible, and that products containing nanomaterials be subject to new safety testing requirements prior to their commercial release. Yet regulations world-wide still fail to distinguish between materials in their nanoscale and bulk form. This means that nanomaterials remain effectively unregulated; there is no regulatory requirement for nanomaterials to face new health and safety testing or environmental impact assessment prior to their use in commercial products, if these materials have already been approved in bulk form.
−
*[http://CRNano.org Center for Responsible Nanotechnology]
 
−
*[http://www.law.harvard.edu/programs/lwp Labor and Worklife Program at Harvard Law School, Nanotechnology Initiative]
 
−
*[http://www.etcgroup.org ETC group] Action group on Erosion, Technology and Concentration
 
−
*[http://www.bioethicsanddisability.org/nanotechnology.html Bioethics and Disability] Nanotechnology
 
−
*[http://www.nanotechwatch.org NanotechWatch.org] Nanotechnology news: the hype and the reality of this emerging technology
 
−
*[http://cns.ucsb.edu/index.html CNS-UCSB]  Center for Nanotechnology in Society
 
  
−
====Other====
+
The health risks of nanomaterials are of particular concern for workers who may face occupational exposure to nanomaterials at higher levels, and on a more routine basis, than the general public.
−
* [http://www.nanodaddy.com Latest Nanotechnology Research News and Careers]
 
−
* [http://www.ntcgmbh.com Research Results used in Industrial Applications ]
 
−
* [http://www.nanotechnology.com/ Nanotechnology.com] News, information, and exclusive articles
 
−
* [http://www.nano-map.de Nano-map.de] - Nano-map is a graphical tool for the visualization of the regional distribution of relevant nanotechnology institutions in Germany including major enterprises, SMEs, networks, research centers, university institutes, funding agencies, technology transfer and financing institutions.
 
−
* [http://www.nanowerk.com/ Nanowerk] - A free database to research 800 nanomaterials from over 75 manufacturers
 
−
* [http://www.foresight.org/ Foresight Institute]
 
−
* [http://icon.rice.edu/ International Council on Nanotechnology]
 
−
* [http://www.MolecularAssembler.com Molecular Assembler website]
 
−
* [http://www.nanoindian.com Nanotechnology in India]
 
−
* [http://www.nanobuildings.com/ NanoBuildings - Buildings for Advanced Technology Workshops]
 
−
* [http://www.nano.gov/ National Nanotechnology Initiative]
 
−
* [http://nanoDiamond.info/ NanoDiamond] atomic level design of a very high strength-to-weight ratio material
 
−
* [http://www.nanotec2005.com/ Nanotec Congress in Brazil]
 
−
* [http://nprl.bham.ac.uk/ UK research]
 
−
* [http://www.wise-nano.org Wise-Nano] A Wiki project, initiated by the [http://crnano.org/ Center for Responsible Nanotechnology] and devoted to [[Molecular engineering|Molecular Manufacturing]]
 
−
*[http://www.etcgroup.org/article.asp?newsid=375 The Big Down] - The first Civil Society Critique of Nanoscale technologies from [http://www.etcgroup.org ETC Group]
 
−
* [[PNAS]] supplement: [http://www.pnas.org/content/vol99/suppl_2/ ''Nanoscience: Underlying Physical Concepts and Phenomena'']
 
−
* [http://www.nanomedicine.com Medical nanorobotics textbooks online]
 
−
* [http://www.zyvex.com/nano/ Nanotechnology by Dr.Ralph Merkle]
 
−
* [http://www.nanoindustries.com/ Nanotechnology Industries]
 
−
* [http://www.knhproductions.ca/nisnano/ Documentary on Nanotechnology]
 
−
* [http://www.human-evolution.org/nano.php Nanotechnology: Is it Real?]
 
−
* [http://www.physorg.com/news3415.html Plasmons (Physorg)]
 
−
* [http://www.nanocrete.com nanotechnology applied to concrete manufacturing]
 
−
* [http://whatsnextnetwork.com/technology/index.php/2005/06/22/nanoparticles_transport_cancer_killing_d Nanotechnology & Cancer Cures]
 
−
* [http://www.nanotechnologybasics.com/ Nanotechnology Basics]
 
−
* [http://www.microtec-d.com Nanomaterials used in BioMEMS]
 
−
* [http://www.nano-biology.net Nanomedicine Resources - labs, literature, jobs, news, discussion - academic focus]
 
−
* [http://www.micronit.com Nanofluidics]
 
−
* [http://www.michaelmarshallsmith.com/books.htm#wymi Short Story, "Hell Hath Enlarged Herself", by Michael Marshall Smith.]  Deals with possible worst-case outcome of nanotechnology.
 
  
−
====Scientists in the Field====
+
=== Broader societal implications and challenges ===
  
−
Dr. David G. Grier, of New York University, has developed a method of rapidly modulating laser beams via a dynamic [[spatial light modulator]] (SLM) in the form of a phase only hologram. (http://www.physics.nyu.edu/grierlab/)[[robots]]
+
Beyond the toxicity risks to human health and the environment which are associated with first-generation nanomaterials, nanotechnology has broader societal implications and poses broader social challenges. Social scientists have suggested that nanotechnology's social issues should be understood and assessed not simply as "downstream" risks or impacts, but as challenges to be factored into "upstream" research and decision making, in order to ensure technology development that meets social objectives. Many social scientists and civil society organisations further suggest that [[technology assessment]] and governance should also involve public participation <ref>Phil Macnaghten, et al. [http://csec.lancs.ac.uk/docs/nano%20project%20sci%20com%20proofs%20nov05.pdf "Nanotechnology, Governance, and Public Deliberation: What Role for Social Sciences?"] ''Science Communication'' 27 (2) (Dec 2005):1-24. Retrieved June 29, 2007.</ref>.
  
−
== References ==
+
Some observers suggest that nanotechnology will build incrementally, as did the eighteenth and nineteenth century [[industrial revolution]], until it gathers pace to drive a nanotechnological revolution that will radically reshape our economies, our labor markets, international trade, international relations, social structures, civil liberties, our relationship with the natural world and even what we understand to be human. Others suggest that it may be more accurate to describe nanotechnology-driven changes as a “technological [[tsunami]].”
  
−
* {{Book reference|Author=Daniel J. Shanefield|Year=1996|Title=Organic Additives And Ceramic Processing|Publisher=Kluwer Academic Publishers|ID=ISBN 0792397657[http://www.criandoofertas.com.br .]}}
+
The implications of the analysis of such a powerful new technology remain sharply divided. Optimists, including many governments, see nanotechnology delivering environmentally benign material abundance for all by providing universal clean water supplies; atomically engineered food and crops resulting in greater agricultural productivity with less labor requirements; nutritionally enhanced interactive ‘smart’ foods; cheap and powerful [[energy]] generation; clean and highly efficient manufacturing; radically improved formulation of [[drug]]s, diagnostics and organ replacement; much greater [[Information technology|information storage and communication]] capacities; interactive ‘smart’ appliances; and increased human performance through convergent technologies <ref>[http://www.ostp.gov/NSTC/html/iwgn/iwgn.fy01budsuppl/nni.pdf ''National Nanotechnology Initiative''] National Science and Technology Council. (Feb. 2002) Retrieved June 29, 2007.</ref>.
  
−
* [http://www.nanotechproject.org/ Project on Emerging Nanotechnologies]
+
Nano skeptics suggest that nanotechnology will simply exacerbate problems stemming from existing socio-economic inequity and the unequal distribution of power by creating greater inequities between rich and poor through an inevitable nano-divide (the gap between those who control the new nanotechnologies and those whose products, services or labor are displaced by them); destabilizing international relations through a growing nano arms race and increased potential for [[bioweapon]]ry; providing the tools for ubiquitous surveillance, with significant implications for [[civil liberty]]; breaking down the barriers between life and non-life through [[nanobiotechnology]], and redefining even what it means to be human.
  
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* [http://cben.rice.edu/ Centre for Biological and Environmental Nanotechnology]
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== See also ==
  
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* [http://www.nanobusiness.org/ NanoBusiness Alliance]
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* [[Carbon]]
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* [[Fullerene]]
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* [[Molecule]]
  
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* {{Book reference|Author=Hunt, Geoffrey & Mehta, Michael (eds)|Year=2006|Title=Nanotechnology: Risk Ethics, & Law|Publisher=Earthscan, London| date:2006]}}
+
== Notes ==
 +
<references/>
  
 +
==References==
 +
 +
* Drexler, K. Eric [http://www.imm.org/PNAS.html ''Molecular engineering: An approach to the development of general capabilities for molecular manipulation''] Retrieved June 29, 2007.
 +
* Friends of the Earth "Nanotechnology, sunscreens and cosmetics: Small ingredients, big risks" Friends of the Earth, 2006.
 +
* Hoet, Peter H.M., et al. [http://www.jnanobiotechnology.com/content/2/1/12 Nanoparticles – known and unknown health risks] ''Journal of Nanobiotechnology'' 2 (2004):12 Retrieved June 29, 2007.
 +
* Jones, Richard A. L. 2004. ''Soft machines: nanotechnology and life.'' Oxford: Oxford University Press. ISBN 0198528558
 +
* Lakhtakia, A. 2004. ''The handbook of nanotechnology: nanometer structure theory, modelling, and simulation.'' Bellingham, Wash: SPIE. ISBN 081945186X
 +
* Li, Ning, et al. [http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1241427 ''Ultrafine particulate pollutants induce oxidative stress and mitochondrial damage.'']. Retrieved June 29, 2007.
 +
* Nalwa, Hari Singh. 2004. ''Encyclopedia of nanoscience and nanotechnology.'' Stevenson Ranch, Calif: American Scientific Publishers. ISBN 1588830012
 +
* Phoenix, Chris [http://www.crnano.org/developing.htm ''Developing Molecular Manufacturing''] Retrieved June 29, 2007.
 +
* Rieth, Michael, and W. Schommers. 2006. ''Handbook of theoretical and computational nanotechnology.'' Stevenson Ranch, Calif: American Scientific Publishers. ISBN 158883042X
 +
* The Royal Society [http://www.nanotec.org.uk/finalReport.htm Nanoscience and Nanotechnologies: Opportunities and Uncertainties] The Royal Society. Retrieved June 29, 2007.
 +
* Ryman-Rasmussen, Jessica P. et al.[http://toxsci.oxfordjournals.org/cgi/reprint/91/1/159 ''Penetration of Intact skin by Quantum Dots with Diverse Physiochemical Properties''] Retrieved June 29, 2007.
 +
* Smith, Roger [http://www.ctonet.org/documents/Nanotech_analysis.pdf ''Nanotechnology: A Brief Technology Analysis'']''Nanotechnology: A Brief Technology Analysis.'' CTOnet.org, 2004. Retrieved June 29, 2007.
 +
* Sten, Lin. 1999. ''Souls, Slavery, and Survival in the Molenotech Age.'' St. Paul, MN: Paragon House. ISBN 1557787794
 +
* Tolstoshev, Arius [http://www.earthpolicy.org.au/nanotech.pdf ''Nanotechnology: Assessing the Environmental Risks for Australia''] Earth Policy Centre, September 2006. Retrieved June 29, 2007.
 +
*Wang, Fei and A. Lakhtakia. 2006. ''Selected papers on nanotechnology—theory and modeling.'' Bellingham, Wash: SPIE Press.
 +
* Zhao, Yuliang and Hari Singh Nalwa. 2007. ''Nanotoxicology: interactions of nanomaterials with biological systems.'' Nanotechnology book series, 19. Stevenson Ranch, Calif: American Scientific Publishers. ISBN 1588830888
 +
 +
== External links ==
 +
All links retrieved November 10, 2022.
 +
* [http://www.nanotech-now.com Nanotechnology Now]
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* [http://www.nanohub.org/ nanoHUB - Online Nanotechnology resource with simulation programs, seminars and lectures]
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* [http://www.cheresources.com/nanotech1.shtml Capitalizing on Nanotechnolgy's Enormous Promise]
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* [http://www.nanolab.ucla.edu/ UCLA Nanoelectronics Research Facility]
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* [http://www.cnsi.ucla.edu/ California Nanosystems Institute at UCLA]
  
 
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Latest revision as of 02:44, 11 March 2023

Buckminsterfullerene C60, also known as the buckyball, is the simplest of the carbon structures known as fullerenes. Members of the fullerene family are a major subject of research falling under the nanotechnology umbrella.

Nanotechnology is a field of applied science and technology covering a broad range of topics. The main unifying theme is the control of matter on a scale smaller than 1 micrometer, normally between 1-100 nanometers, as well as the fabrication of devices on this same length scale. It is a highly multidisciplinary field, drawing from fields such as colloidal science, device physics, and supramolecular chemistry. Much speculation exists as to what new science and technology might result from these lines of research. Some view nanotechnology as a marketing term that describes pre-existing lines of research applied to the sub-micron size scale.

Despite the apparent simplicity of this definition, nanotechnology actually encompasses diverse lines of inquiry. Nanotechnology cuts across many disciplines, including colloidal science, chemistry, applied physics, materials science, and even mechanical and electrical engineering. It could variously be seen as an extension of existing sciences into the nanoscale, or as a recasting of existing sciences using a newer, more modern term. Two main approaches are used in nanotechnology: one is a "bottom-up" approach where materials and devices are built from molecular components which assemble themselves chemically using principles of molecular recognition; the other being a "top-down" approach where nano-objects are constructed from larger entities without atomic-level control.

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). Combined with refined processes such as electron beam lithography and molecular beam epitaxy, these instruments allow the deliberate manipulation of nanostructures, and in turn led to the observation of novel phenomena. 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. 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 clothing.

"Buckyball" C60 molecule
Topics
History · Implications
Applications · Organizations
Popular culture · List of topics
Subfields and related fields
Nanomedicine
Molecular self-assembly
Molecular electronics
Scanning probe microscopy
Nanolithography
Molecular nanotechnology
Nanomaterials
Nanomaterials · Fullerene
Carbon nanotubes
Fullerene chemistry
Applications · Popular culture
Timeline · Carbon allotropes
Nanoparticles · Quantum dots
Colloidal gold · Colloidal silver
Molecular nanotechnology
Molecular assembler
Mechanosynthesis
Nanorobotics · Grey goo
K. Eric Drexler
Engines of Creation

History

Nanoscience and nanotechnology only became possible in the 1910s with the development of the first tools to measure and make nanostructures. But the actual development started with the discovery of electrons and neutrons which showed scientists that matter can really exist on a much smaller scale than what we normally think of as small, and/or what they thought was possible at the time. It was at this time when curiosity for nanostructures had originated.

The atomic force microscope (AFM) and the Scanning Tunneling Microscope (STM) are two early versions of scanning probes that launched nanotechnology. There are other types of scanning probe microscopy, all flowing from the ideas of the scanning confocal microscope developed by Marvin Minsky in 1961 and the scanning acoustic microscope (SAM) developed by Calvin Quate and coworkers in the 1970s, that made it possible to see structures at the nanoscale. The tip of a scanning probe can also be used to manipulate nanostructures (a process called positional assembly). Feature-oriented scanning-positioning methodology suggested by Rostislav Lapshin appears to be a promising way to implement these nanomanipulations in automatic mode. However, this is still a slow process because of low scanning velocity of the microscope. Various techniques of nanolithography such as dip pen nanolithography, electron beam lithography or nanoimprint lithography were also developed. Lithography is a top-down fabrication technique where a bulk material is reduced in size to nanoscale pattern.

The first distinguishing concepts in nanotechnology (but predating use of that name) was in "There's Plenty of Room at the Bottom," a talk given by physicist Richard Feynman at an American Physical Society meeting at Caltech on December 29, 1959 [1]. Feynman described a process by which the ability to manipulate individual atoms and molecules might be developed, using one set of precise tools to build and operate another proportionally smaller set, so on down to the needed scale. In the course of this, he noted, scaling issues would arise from the changing magnitude of various physical phenomena: gravity would become less important, surface tension and Van der Waals attraction would become more important. This basic idea appears feasible, and exponential assembly enhances it with parallelism to produce a useful quantity of end products.

Eight allotropes of Carbon

The term "nanotechnology" was defined by Tokyo Science University Professor Norio Taniguchi in a 1974 paper [2] as follows: "'Nano-technology' mainly consists of the processing of, separation, consolidation, and deformation of materials by one atom or by one molecule." In the 1980s the basic idea of this definition was explored in much more depth by Dr. K. Eric Drexler, who promoted the technological significance of nano-scale phenomena and devices through speeches and the book Engines of Creation: The Coming Era of Nanotechnology[3], and so the term acquired its current sense.

Nanotechnology and nanoscience got started in the early 1980s with two major developments; the birth of cluster science and the invention of the scanning tunneling microscope (STM). This development led to the discovery of fullerenes in 1986 and carbon nanotubes a few years later. In another development, the synthesis and properties of semiconductor nanocrystals was studied. This led to a fast increasing number of metal oxide nanoparticles of quantum dots. The atomic force microscope was invented five years after the STM was invented. The AFM uses atomic force to "see" the atoms.

Fundamental concepts

One nanometer (nm) is one billionth, or 10-9 of a meter. For comparison, typical carbon-carbon bond lengths, or the spacing between these atoms in a molecule, are in the range .12-.15 nm, and a DNA double-helix has a diameter around 2 nm. On the other hand, the smallest cellular lifeforms, the bacteria of the genus Mycoplasma, are around 200 nm in length.

Larger to smaller: a materials perspective

Image of reconstruction on a clean Au(100) surface, as visualized using scanning tunneling microscopy. The individual atoms composing the surface are visible.

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. A number of physical phenomena become noticeably pronounced as the size of the system decreases. These include statistical mechanical effects, as well as quantum mechanical effects, for example the “quantum size effect” where the electronic properties of solids are altered with great reductions in particle size. This effect does not come into play by going from macro to micro dimensions. However, it becomes dominant when the nanometer size range is reached. Additionally, a number of physical properties change when compared to macroscopic systems. One example is the increase in surface area to volume of materials.

Materials reduced to the nanoscale can suddenly show very different properties compared to what they exhibit on a macroscale, enabling unique applications. For instance, opaque substances become transparent (copper); inert materials become catalysts (platinum); stable materials turn combustible (aluminum); solids turn into liquids at room temperature (gold); insulators become conductors (silicon). A material such as gold, which is chemically inert at normal scales, can serve as a potent chemical catalyst at nanoscales. Much of the fascination with nanotechnology stems from these unique quantum and surface phenomena that matter exhibits at the nanoscale.

Simple to complex: a molecular perspective

Modern synthetic chemistry has reached the point where it is possible to prepare small molecules to almost any structure. These methods are used today to produce a wide variety of useful chemicals such as pharmaceuticals or commercial polymers. This ability raises the question of extending this kind of control to the next-larger level, seeking methods to assemble these single molecules into supramolecular assemblies consisting of many molecules arranged in a well defined manner.

These approaches utilize the concepts of molecular self-assembly and/or supramolecular chemistry to automatically arrange themselves into some useful conformation through a bottom-up approach. The concept of molecular recognition is especially important: molecules can be designed so that a specific conformation or arrangement is favored. The Watson-Crick basepairing rules are a direct result of this, as is the specificity of an enzyme being targeted to a single substrate, or the specific folding of the protein itself. Thus, two or more components can be designed to be complementary and mutually attractive so that they make a more complex and useful whole.

Such bottom-up approaches should, broadly speaking, be able to produce devices in parallel and much cheaper than top-down methods, but could potentially be overwhelmed as the size and complexity of the desired assembly increases. Most useful structures require complex and thermodynamically unlikely arrangements of atoms. Nevertheless, there are many examples of self-assembly based on molecular recognition in biology, most notably Watson-Crick basepairing and enzyme-substrate interactions. The challenge for nanotechnology is whether these principles can be used to engineer novel constructs in addition to natural ones.

Molecular nanotechnology

Molecular nanotechnology, sometimes called molecular manufacturing, is a term given to the concept of engineered nanosystems (nanoscale machines) operating on the molecular scale. It is especially associated with the concept of a molecular assembler, a machine that can produce a desired structure or device atom-by-atom using the principles of mechanosynthesis. 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.

When the term "nanotechnology" was independently coined and popularized by Eric Drexler (who at the time was unaware of an earlier usage by Norio Taniguchi) 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 molecular machines were possible: by the countless examples found in biology, it is known that billions of years of evolutionary feedback can produce sophisticated, stochastically optimized biological machines. It is hoped that developments in nanotechnology will make possible their construction by some other means, perhaps using biomimetic principles. However, Drexler and other researchers have proposed that advanced nanotechnology, although perhaps initially implemented by biomimetic means, ultimately could be based on mechanical engineering principles, namely, a manufacturing technology based on the mechanical functionality of these components (such as gears, bearings, motors, and structural members) that would enable programmable, positional assembly to atomic specification PNAS-1981. The physics and engineering performance of exemplar designs were analyzed in Drexler's book [4]. But Drexler's analysis is very qualitative and does not address very pressing issues, such as the "fat fingers" and "Sticky fingers" problems, which are problems related to the difficulty in handling and assembling on the nanoscale. In general it is very difficult to assemble devices on the atomic scale, as all one has to position atoms are other atoms of comparable size and stickiness.

Another view, put forth by Carlo Montemagno [5] is that future nanosystems will be hybrids of silicon technology and biological molecular machines. Yet another view, put forward by the late Richard Smalley, is that mechanosynthesis is impossible due to the difficulties in mechanically manipulating individual molecules. This led to an exchange of letters [6] in the ACS publication Chemical & Engineering News in 2003.

Though biology clearly demonstrates that molecular machine systems are possible, non-biological molecular machines are today only in their infancy. Leaders in research on non-biological molecular machines are Dr. Alex Zettl and his colleagues at Lawrence Berkeley Laboratories and UC Berkeley. They have constructed at least three distinct molecular devices whose motion is controlled from the desktop with changing voltage: a nanotube nanomotor, a molecular actuator [7], and a nanoelectromechanical relaxation oscillator [8] An experiment indicating that positional molecular assembly is possible was performed by Ho and Lee at Cornell University in 1999. They used a scanning tunneling microscope to move an individual carbon monoxide molecule (CO) to an individual iron atom (Fe) sitting on a flat silver crystal, and chemically bound the CO to the Fe by applying a voltage.

Current research

Graphical representation of a rotaxane, useful as a molecular switch.
This device transfers energy from nano-thin layers of quantum wells to nanocrystals above them, causing the nanocrystals to emit visible light [9]

Nanotechnology is a very broad term, there are many different but sometimes overlapping subfields that could fall under its umbrella. The following avenues of research could be considered subfields of nanotechnology. Note that these categories are not concrete and a single subfield may overlap many of them, especially as the field of nanotechnology continues to mature.

Nanomaterials

This 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.
  • Nanoscale materials can also be used for bulk applications; most present commercial applications of nanotechnology are of this flavor.
  • Progress has been made in using these materials for medical applications.

Bottom-up approaches

These seek to arrange smaller components into more complex assemblies.

  • DNA Nanotechnology utilizes the specificity of Watson-Crick basepairing to construct well-defined structures out of DNA and other nucleic acids.
  • More generally, molecular self-assembly seeks to use concepts of supramolecular chemistry, and molecular recognition in particular, to cause single-molecule components to automatically arrange themselves into some useful conformation.

Top-down approaches

These 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 features smaller than 100 nm, falling under the definition of nanotechnology. Giant magnetoresistance-based hard disk drives already on the market fit this description, as do atomic layer deposition (ALD) techniques.
  • Solid-state techniques can also be used to create devices known as nanoelectromechanical systems or NEMS, which are related to microelectromechanical systems (MEMS).
  • Atomic force microscope tips can be used as a nanoscale "write head" to deposit a chemical on a surface in a desired pattern in a process called dip pen nanolithography. This fits into the larger subfield of nanolithography.

Functional approaches

These seek to develop components of a desired functionality without regard to how they might be assembled.

  • Molecular electronics seeks to develop molecules with useful electronic properties. These could then be used as single-molecule components in a nanoelectronic device.
  • Synthetic chemical methods can also be used to create synthetic molecular motors, such as in a so-called nanocar.

Speculative

These subfields seek to anticipate what inventions nanotechnology might yield, or attempt to propose an agenda along which inquiry might progress. These often take a big-picture view of nanotechnology, with more emphasis on its societal implications than the details of how such inventions could actually be created.

  • Molecular nanotechnology is a proposed approach which involves manipulating single molecules in finely controlled, deterministic ways. This is more theoretical than the other subfields and is beyond current capabilities.
  • Nanorobotics centers on self-sufficient machines of some functionality operating at the nanoscale. There are hopes for applying nanorobots in medicine [10] [11] [12], while it might not be easy to do such a thing because of several drawbacks of such devices

[13] Nevertheless, progress on innovative materials and methodologies has been demonstrated with some patents granted about new nanomanufacturing devices for future commercial applications, which also progressively helps in the development towards nanorobots with the use of embedded nanobioelectronics concept.

  • Programmable matter based on artificial atoms seeks to design materials whose properties can be easily and reversibly externally controlled.
  • Due to the popularity and media exposure of the term nanotechnology, the words picotechnology and femtotechnology have been coined in analogy to it, although these are only used rarely and informally.

Tools and techniques

Typical AFM setup. A microfabricated cantilever with a sharp tip is deflected by features on a sample surface, much like in a phonograph but on a much smaller scale. A laser beam reflects off the backside of the cantilever into a set of photodetectors, allowing the deflection to be measured and assembled into an image of the surface.

Another technique uses SPT™s (surface patterning tool) as the molecular “ink cartridge.” Each SPT is a microcantilever-based micro-fluidic handling device. SPTs contain either a single microcantilever print head or multiple microcantilevers for simultaneous printing of multiple molecular species. The integrated microfluidic network transports fluid samples from reservoirs located on the SPT through microchannels to the distal end of the cantilever. Thus SPTs can be used to print materials that include biological samples such as proteins, DNA, RNA, and whole viruses, as well as non-biological samples such as chemical solutions, colloids and particle suspensions. SPTs are most commonly used with molecular printers.

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 and which were results of nanotechnology research.

The top-down approach anticipates nanodevices that must be built piece by piece in stages, much as manufactured items are currently made. Scanning probe microscopy is an important technique both for characterization and synthesis of nanomaterials. Atomic force microscopes and scanning tunneling microscopes can be used to look at surfaces and to move atoms around. By designing different tips for these microscopes, they can be used for carving out structures on surfaces and to help guide self-assembling structures. By using, for example, feature-oriented scanning-positioning approach, atoms can be moved around on a surface with scanning probe microscopy techniques. At present, it is expensive and time-consuming for mass production but very suitable for laboratory experimentation.

In contrast, bottom-up techniques build or grow larger structures atom by atom or molecule by molecule. These techniques include chemical synthesis, self-assembly and positional assembly. Another variation of the bottom-up approach is molecular beam epitaxy or MBE. Researchers at Bell Telephone Laboratories like John R. Arthur, Alfred Y. Cho, and Art C. Gossard developed and implemented MBE as a research tool in the late 1960s and 1970s. Samples made by MBE were key to the discovery of the fractional quantum Hall effect for which the 1998 Nobel Prize in Physics was awarded. MBE allows scientists to lay down atomically-precise layers of atoms and, in the process, build up complex structures. Important for research on semiconductors, MBE is also widely used to make samples and devices for the newly emerging field of spintronics.

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

Applications

Although there has been much hype about the potential applications of nanotechnology, most current commercialized applications are limited to the use of "first generation" passive nanomaterials. These include titanium dioxide nanoparticles in sunscreen, cosmetics and some food products; silver nanoparticles in food packaging, clothing, disinfectants and household appliances; zinc oxide nanoparticles in sunscreens and cosmetics, surface coatings, paints and outdoor furniture varnishes; and cerium oxide nanoparticles as a fuel catalyst. The Woodrow Wilson Center for International Scholars' Project on Emerging Nanotechnologies hosts an inventory of consumer products which now contain nanomaterials[14]

However further applications which require actual manipulation or arrangement of nanoscale components await further research. Though technologies currently branded with the term 'nano' are sometimes little related to and fall far short of the most ambitious and transformative technological goals of the sort in molecular manufacturing proposals, the term still connotes such ideas. Thus there may be a danger that a "nano bubble" will form, or is forming already, from the use of the term by scientists and entrepreneurs to garner funding, regardless of interest in the transformative possibilities of more ambitious and far-sighted work.

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.[15]" This published study 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."

Implications

Due to the far-ranging claims that have been made about potential applications of nanotechnology, a number of concerns have been raised about what effects these will have on our society if realized, and what action if any is appropriate to mitigate these risks. Short-term issues include the effects that widespread use of nanomaterials would have on human health and the environment. Longer-term concerns center on the implications that new technologies will have for society at large, and whether these could possibly lead to either a post scarcity economy, or alternatively exacerbate the wealth gap between developed and developing nations.

Health and environmental issues

There is a growing body of scientific evidence which demonstrates the potential for some nanomaterials to be toxic to humans or the environment [16][17][18].

The smaller a particle, the greater its surface area to volume ratio and the higher its chemical reactivity and biological activity. The greater chemical reactivity of nanomaterials results in increased production of reactive oxygen species (ROS), including free radicals. ROS production has been found in a diverse range of nanomaterials including carbon fullerenes, carbon nanotubes and nanoparticle metal oxides. ROS and free radical production is one of the primary mechanisms of nanoparticle toxicity; it may result in oxidative stress, inflammation, and consequent damage to proteins, membranes and DNA [19].

The extremely small size of nanomaterials also means that they are much more readily taken up by the human body than larger sized particles. Nanomaterials are able to cross biological membranes and access cells, tissues and organs that larger-sized particles normally cannot. Nanomaterials can gain access to the blood stream following inhalation or ingestion . At least some nanomaterials can penetrate the skin; even larger microparticles may penetrate skin when it is flexed . Broken skin is an ineffective particle barrier, suggesting that acne, eczema, wounds or severe sunburn may enable skin uptake of nanomaterials more readily. Once in the blood stream, nanomaterials can be transported around the body and are taken up by organs and tissues including the brain, heart, liver, kidneys, spleen, bone marrow and nervous system. Nanomaterials have proved toxic to human tissue and cell cultures, resulting in increased oxidative stress, inflammatory cytokine production and cell death . Unlike larger particles, nanomaterials may be taken up by cell mitochondria and the cell nucleus. Studies demonstrate the potential for nanomaterials to cause DNA mutation and induce major structural damage to mitochondria, even resulting in cell death.

Size is therefore a key factor in determining the potential toxicity of a particle. However it is not the only important factor. Other properties of nanomaterials that influence toxicity include: chemical composition, shape, surface structure, surface charge, aggregation and solubility, and the presence or absence of functional groups of other chemicals . The large number of variables influencing toxicity means that it is difficult to generalize about health risks associated with exposure to nanomaterials – each new nanomaterial must be assessed individually and all material properties must be taken into account.

In its seminal 2004 report[20], the United Kingdom's Royal Society recommended that nanomaterials be regulated as new chemicals, that research laboratories and factories treat nanomaterials "as if they were hazardous," that release of nanomaterials into the environment be avoided as far as possible, and that products containing nanomaterials be subject to new safety testing requirements prior to their commercial release. Yet regulations world-wide still fail to distinguish between materials in their nanoscale and bulk form. This means that nanomaterials remain effectively unregulated; there is no regulatory requirement for nanomaterials to face new health and safety testing or environmental impact assessment prior to their use in commercial products, if these materials have already been approved in bulk form.

The health risks of nanomaterials are of particular concern for workers who may face occupational exposure to nanomaterials at higher levels, and on a more routine basis, than the general public.

Broader societal implications and challenges

Beyond the toxicity risks to human health and the environment which are associated with first-generation nanomaterials, nanotechnology has broader societal implications and poses broader social challenges. Social scientists have suggested that nanotechnology's social issues should be understood and assessed not simply as "downstream" risks or impacts, but as challenges to be factored into "upstream" research and decision making, in order to ensure technology development that meets social objectives. Many social scientists and civil society organisations further suggest that technology assessment and governance should also involve public participation [21].

Some observers suggest that nanotechnology will build incrementally, as did the eighteenth and nineteenth century industrial revolution, until it gathers pace to drive a nanotechnological revolution that will radically reshape our economies, our labor markets, international trade, international relations, social structures, civil liberties, our relationship with the natural world and even what we understand to be human. Others suggest that it may be more accurate to describe nanotechnology-driven changes as a “technological tsunami.”

The implications of the analysis of such a powerful new technology remain sharply divided. Optimists, including many governments, see nanotechnology delivering environmentally benign material abundance for all by providing universal clean water supplies; atomically engineered food and crops resulting in greater agricultural productivity with less labor requirements; nutritionally enhanced interactive ‘smart’ foods; cheap and powerful energy generation; clean and highly efficient manufacturing; radically improved formulation of drugs, diagnostics and organ replacement; much greater information storage and communication capacities; interactive ‘smart’ appliances; and increased human performance through convergent technologies [22].

Nano skeptics suggest that nanotechnology will simply exacerbate problems stemming from existing socio-economic inequity and the unequal distribution of power by creating greater inequities between rich and poor through an inevitable nano-divide (the gap between those who control the new nanotechnologies and those whose products, services or labor are displaced by them); destabilizing international relations through a growing nano arms race and increased potential for bioweaponry; providing the tools for ubiquitous surveillance, with significant implications for civil liberty; breaking down the barriers between life and non-life through nanobiotechnology, and redefining even what it means to be human.

See also

Notes

  1. ↑ Alan Chodos, (ed.) American Physics Society"December 29, 1959: Feynman's Classic CalTech Lecture." Retrieved June 28, 2007.
  2. ↑ N. Taniguchi. "On the Basic Concept of 'Nano-Technology'." Proc. Intl. Conf. Prod. Eng. Part II, (1974) (Tokyo: Japan Society of Precision Engineering)
  3. ↑ K. Eric Drexler. 1992. Nanosystems: molecular machinery, manufacturing, and computation. (New York: Wiley. ISBN 0471575186) Nanosystems: Molecular Machinery, Manufacturing, and Computation.
  4. ↑ Ibid. Nanosystems: Molecular Machinery, Manufacturing, and Computation
  5. ↑ Carlo Montemagno, UCLA People: "Carlo Montemagno." Retrieved November 30, 2007.
  6. ↑ American Chemical and Engineering News Retrieved June 28, 2007.
  7. ↑ B. C. Regan, et al. Nano Letters 5(9)(2005):1730-1733.Nano Crystal Powered Motor Retrieved June 28, 2007.
  8. ↑ B. C. Regan, et al. "Surface-tesion-driven nanoelectromechanical relaxation" Applied Physics Letters 86 (2005):123119.(UC Berkeley).
  9. ↑ Wireless nanocrystals efficiently radiate visible light Sandina National Labs. Retrieved June 28, 2007.
  10. ↑ Z. Ghalanbor, S.A. Marashi, and B. Ranjbar. 2005. "Nanotechnology helps medicine: nanoscale swimmers and their future applications." Medical Hypotheses 65 (1): 198-199.
  11. ↑ T. Kubik, K. Bogunia-Kubik, and M. Sugisaka. 2005. "Nanotechnology on duty in medical applications." Current Pharmaceutical Biotechnology 6 (1): 17-33.
  12. ↑ A. Cavalcanti, and R.A. Freitas, Jr. 2005. "Nanorobotics control design: a collective behavior approach for medicine." IEEE Transactions on Nanobioscience 4 (2): 133-140.
  13. ↑ R.C. Shetty. 2005. "Potential pitfalls of nanotechnology in its applications to medicine: immune incompatibility of nanodevices." Medical Hypotheses 65 (5): 998-999.
  14. ↑ A Nanotechnology Consumer Products Inventory Woodrow Wilson International Center for Scholars Retrieved June 29, 2007.
  15. ↑ David M. Berube. 2006. Nano-hype: the truth behind the nanotechnology buzz. (Amherst, NY: Prometheus Books. ISBN 1591023513)
  16. ↑ Peter HM Hoet, et al. "Nanoparticles – known and unknown health risks." Journal of Nanobiotechnology 2(2004):12 Nanoparticles – known and unknown health risksReview and Abstract. Retrieved June 28, 2007.
  17. ↑ Gunter Oberdorster. "Nanotoxicology: An Emerging Discipline Evolving from Studies of Ultrafine Particles." Environmental Health Perspectives 113 (7) (July 2005) Review and Abstract. Retrieved June 28, 2007.
  18. ↑ Günter Oberdörster, et al. Particle and Fibre Toxicology Particle and Fibre Toxicology Retrieved June 28, 2007.
  19. ↑ A. Nel, T. Xia, L. Mưadler, and N. Li. 2006. "Toxic potential of materials at the nanolevel." Science 311(5761)(2006):622-627.
  20. ↑ Nanoscience and nanotechnologies: opportunities and uncertainties The Royal Society Retrieved June 29, 2007.
  21. ↑ Phil Macnaghten, et al. "Nanotechnology, Governance, and Public Deliberation: What Role for Social Sciences?" Science Communication 27 (2) (Dec 2005):1-24. Retrieved June 29, 2007.
  22. ↑ National Nanotechnology Initiative National Science and Technology Council. (Feb. 2002) Retrieved June 29, 2007.

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