Nanotechnology

Nanotechnology is the manipulation of matter with at least one dimension sized from 1 to 100 nanometers (nm). At this scale, commonly known as the nanoscale, surface area and quantum mechanical effects become important in describing properties of matter. This definition of nanotechnology includes all types of research and technologies that deal with these special properties. It is common to see the plural form "nanotechnologies" as well as "nanoscale technologies" to refer to research and applications whose common trait is scale. An earlier understanding of nanotechnology referred to the particular technological goal of precisely manipulating atoms and molecules for fabricating macroscale products, now referred to as molecular nanotechnology.

A near-synonym of "nanotechnology" is nanoscience (i.e., nanophysics, nanochemistry, nanobiology and nanoinformatics); however, the term "nanoscience" emphasizes the pure science aspects of the field, whilst nanotechnology, methods and processes (e.g., nanolithography and nanobiosensing) are the concrete output of applied nanosciences (e.g., nanoengineering and nanomedicine).

Nanotechnology defined by scale includes fields of science such as surface science, organic chemistry, molecular biology, semiconductor physics, energy storage, engineering, microfabrication, and molecular engineering. The associated research and applications range from extensions of conventional device physics to [molecular self-assembly](/wiki/molecular-self-assembly), from developing new materials with dimensions on the nanoscale to direct control of matter on the atomic scale.

Nanotechnology may be able to create new materials and devices with diverse applications, such as in nanomedicine, nanoelectronics, agricultural sectors, biomaterials energy production, and consumer products. However, nanotechnology raises issues, including concerns about the toxicity and environmental impact of nanomaterials, and their potential effects on global economics, as well as various doomsday scenarios. These concerns have led to a debate among advocacy groups and governments on whether special regulation of nanotechnology is warranted.

Origins

The concepts that seeded nanotechnology were first discussed in 1959 by physicist Richard Feynman in his talk There's Plenty of Room at the Bottom, in which he described the possibility of synthesis via direct manipulation of atoms.

The term "nano-technology" was first used by Norio Taniguchi in 1974, though it was not widely known. Inspired by Feynman's concepts, K. Eric Drexler used the term "nanotechnology" in his 1986 book Engines of Creation: The Coming Era of Nanotechnology, which achieved popular success and helped thrust nanotechnology into the public sphere. In it, he proposed the idea of a nanoscale "assembler" that would be able to build a copy of itself and of other items of arbitrary complexity with atom-level control. Also in 1986, Drexler co-founded The Foresight Institute to increase public awareness and understanding of nanotechnology concepts and implications.

The emergence of nanotechnology as a field in the 1980s occurred through the convergence of Drexler's theoretical and public work, which developed and popularized a conceptual framework, and experimental advances that drew additional attention to the prospects. In the 1980s, two breakthroughs helped to spark the growth of nanotechnology. First, the invention of the scanning tunneling microscope in 1981 enabled visualization of individual atoms and bonds, and was successfully used to manipulate individual atoms in 1989. The microscope's developers Gerd Binnig and Heinrich Rohrer at IBM Zurich Research Laboratory received a Nobel Prize in Physics in 1986. Binnig, Quate and Gerber also invented the analogous atomic force microscope that year.

Second, fullerenes (buckyballs) were discovered in 1985 by Harry Kroto, Richard Smalley, and Robert Curl, who together won the 1996 Nobel Prize in Chemistry. C60 was not initially described as nanotechnology; the term was used regarding subsequent work with related carbon nanotubes (sometimes called graphene tubes or Bucky tubes) which suggested potential applications for nanoscale electronics and devices. The discovery of carbon nanotubes is attributed to Sumio Iijima of NEC in 1991, for which Iijima won the inaugural 2008 Kavli Prize in Nanoscience.

In the early 2000s, the field garnered increased scientific, political, and commercial attention that led to both controversy and progress. Controversies emerged regarding the definitions and potential implications of nanotechnologies, exemplified by the Royal Society's report on nanotechnology. Challenges were raised regarding the feasibility of applications envisioned by advocates of molecular nanotechnology, which culminated in a public debate between Drexler and Smalley in 2001 and 2003.

Meanwhile, commercial products based on advancements in nanoscale technologies began emerging. These products were limited to bulk applications of nanomaterials and did not involve atomic control of matter. Some examples include the Silver Nano platform for using silver nanoparticles as an antibacterial agent, nanoparticle-based sunscreens, carbon fiber strengthening using silica nanoparticles, and carbon nanotubes for stain-resistant textiles.

Governments moved to promote and fund research into nanotechnology, such as American the National Nanotechnology Initiative, which formalized a size-based definition of nanotechnology and established research funding, and in Europe via the European Framework Programmes for Research and Technological Development.

By the mid-2000s scientific attention began to flourish. Nanotechnology roadmaps centered on atomically precise manipulation of matter and discussed existing and projected capabilities, goals, and applications.

Fundamental concepts

Nanotechnology is the science and engineering of functional systems at the molecular scale. In its original sense, nanotechnology refers to the projected ability to construct items from the bottom up making complete, high-performance products.

One nanometer (nm) is one billionth, or 10−9, of a meter. By comparison, typical carbon–carbon bond lengths, or the spacing between these atoms in a molecule, are in the range 0.12–0.15 nm, and DNA's diameter is around 2 nm. On the other hand, the smallest cellular life forms, the bacteria of the genus Mycoplasma, are around 200 nm in length. By convention, nanotechnology is taken as the scale range 1 to 100 nm, following the definition used by the American National Nanotechnology Initiative. The lower limit is set by the size of atoms (hydrogen has the smallest atoms, which have an approximately 0.25 nm kinetic diameter). The upper limit is more or less arbitrary, but is around the size below which phenomena not observed in larger structures start to become apparent and can be made use of. These phenomena make nanotechnology distinct from devices that are merely miniaturized versions of an equivalent macroscopic device; such devices are on a larger scale and come under the description of microtechnology.

To put that scale in another context, the comparative size of a nanometer to a meter is the same as that of a marble to the size of the earth.

Two main approaches are used in nanotechnology. In the "bottom-up" approach, materials and devices are built from molecular components which assemble themselves chemically by principles of molecular recognition. In the "top-down" approach, nano-objects are constructed from larger entities without atomic-level control.

Areas of physics such as nanoelectronics, nanomechanics, nanophotonics and nanoionics have evolved to provide nanotechnology's scientific foundation.

Larger to smaller: a materials perspective

Several phenomena become pronounced as system size decreases. These include statistical mechanical effects, as well as quantum mechanical effects, for example, the "quantum size effect" in which the electronic properties of solids are altered.