Nanotechnology: Part One

Sažetak:

The field of nanotechnology covers a range of ultra-small scale technologies, which result from the ability to measure and manipulate matter at an atomic, molecular or cellular level.
Nanotechnology, in its traditional sense, means building things from the bottom up, with atomic precision however, over the past several decades the definition and application of the technology has changed.

Nanotechnology is the 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, using techniques and tools being developed today to make complete, high performance products.

Nanotechnology is a popular label given to a wide range of ultra-small scale technologies which result from the ability to measure and manipulate matter at an atomic, molecular or cellular level. Strictly speaking it is a misnomer because it is not one thing but plural - nanotechnologies. These encompass some existing science, like the surface chemistry of the small particles used in sunscreen and colloidal materials like milk. They offer new materials and devices. Nanotechnologies could take a miniaturising process like printed circuits still further.

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 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. 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. Or another way of putting it: a nanometer is the amount a man’s beard grows in the time it takes him to raise the razor to his face.

When K. Eric Drexler popularized the word ‘nanotechnology’ in the 1980’s, he was talking about building machines on the scale of molecules, a few nanometers wide-motors, robot arms, and even whole computers, far smaller than a cell. K. Eric Drexler spent the next ten years describing and analyzing these incredible devices, and responding to accusations of science fiction. Meanwhile, mundane technology was developing the ability to build simple structures on a molecular scale. As nanotechnology became an accepted concept, the meaning of the word shifted to encompass the simpler kinds of nanometer-scale technology. The U.S. National Nanotechnology Initiative was created to fund this kind of nanotech: their definition includes anything smaller than 100 nanometers with novel properties.

Much of the work being done today that carries the name ‘nanotechnology’ is not nanotechnology in the original meaning of the word. Nanotechnology, in its traditional sense, means building things from the bottom up, with atomic precision. This theoretical capability was envisioned as early as 1959 by the renowned physicist Richard Feynman.

Based on Feynman’s vision of miniature factories using nanomachines to build complex products, advanced nanotechnology (sometimes referred to as molecular manufacturing) will make use of positionally-controlled mechanochemistry guided by molecular machine systems. Formulating a roadmap for development of this kind of nanotechnology is now an objective of a broadly based technology roadmap project led by Battelle (the manager of several U.S. National Laboratories) and the Foresight Nanotech Institute.

Shortly after this envisioned molecular machinery is created, it will result in a manufacturing revolution, probably causing severe disruption. It also has serious economic, social, environmental, and military implications.

At the atomic level, remarkable new properties emerge, for good or ill. There is a need to test for any adverse health or environmental effects of nano-scale particles for example. New things could also be done - such as constructing devices from atoms upwards, diagnostic devices to monitor body processes, means speed up genetic analysis so that a GP could see immediately from a blood sample what genetic dispositions you may have, particles to travel through the bloodstream to deliver a specific dose of chemical to destroy a particular cancerous cell, making therapeutic implants in the body, etc. Much of this is futurologists’ speculation because a lot of the science is still at the stage of basic research. But the implications are far-reaching.

Although generally nanoparticles are considered an invention of modern science, they actually have a very long history. Specifically, nanoparticles were used by artisans as far back as in the 9th century Mesopotamia for generating a glittering effect on the surface of pot.

Even these days pottery from the Middle Ages and Renaissance often retain a distinct gold or copper colored metallic glitter. This so called lustre is caused by a metallic film that was applied to the transparent surface of a glazing. The lustre can still be visible if the film has resisted atmospheric oxidation and other weathering.

The lustre originates within the film itself, which contains silver and copper nanoparticles, dispersed homogeneously in the glassy matrix of the ceramic glaze. These nanoparticles were created by the artisans by adding copper and silver salts and oxides together with vinegar, ochre, and clay, on the surface of previously-glazed pottery. The object was then placed to a kiln and heated to about 600°C in a reducing atmosphere.

In the heat the glaze would soften, causing the copper and silver ions to migrate into the outer layers of the glaze. There the reducing atmosphere reduced the ions back to metals, which then came together forming the nanoparticles that give the colour and optical effects.

Lustre technique shows that craftsmen had a rather sophisticated empirical knowledge of materials. The technique originates in the islamic world. As Muslims were not allowed to use gold in artistic representations, they had to find a way to create a similar effect without using real gold. The solution they found was using lustre.

Michael Faraday provided the first description, in scientific terms, of the optical properties of nanometer-scale metals in his classic 1857 paper "Experimental relations of gold (and other metals) to light". The first mention of some of the distinguishing concepts in nanotechnology (but predating use of that name) was in 1867 by James Clerk Maxwell when he proposed as a thought experiment a tiny entity known as Maxwell's Demon able to handle individual molecules.

The first observations and size measurements of nano-particles was made during first decade of 20th century. They are mostly associated with Richard Adolf Zsigmondy who made detail study of gold sols and other nanomaterials with sizes down to 10 nm and less. He published a book in 1914. He used ultramicroscope that employs dark field method for seeing particles with sizes much less than light wavelength. Zsigmondy was also the first who used nanometer explicitly for characterizing particle size. He determined it as 1/1,000,000 of millimeter. He developed a first system classification based on particle size in nanometer range.

Finally, the last quarter of 20th century has seen tremendous advances in our ability to control and manipulate light. We can generate light pulses as short as a few femtoseconds (1 fs = 10−15 s). Light too has a size and this size is also on the hundred nanometer scale.

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