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29 September 2012

UNDERSTANDING NANOTECHNOLOGY

The prefix "nano" means one billionth. One nanometer (abbreviated as 1 nm) is 1/1,000,000,000 of a meter, which is close to 1/1,000,000,000 of a yard. To get a sense of the nano scale, a human hair measures 50,000 nanometers across, a bacterial cell measures a few hundred nanometers across, and the smallest features that are commonly etched on a commercial microchip as of February 2002 are around 130 nanometers across. The smallest things seeable with the unaided human eye are 10,000 nanometers across. Just ten hydrogen atoms in a line make up one nanometer. It's really very small indeed.

Nanoscience is, at its simplest, the study of the fundamental principles of molecules and structures with at least one dimension roughly between 1 and 100 nanometers. These structures are known, perhaps uncreatively, as nanostructures. Nanotechnology is the application of these nanostructures into useful nanoscale devices. That isn't a very sexy or fulfilling definition, and it is certainly not one that seems to explain the hoopla. To explain that, it's important to understand that the nanoscale isn't just small, it's a special kind of small.

Anything smaller than a nanometer in size is just a loose atom or small molecule floating in space as a little dilute speck of vapor. So nanostructures aren't just smaller than anything we've made before, they are the smallest solid things it is possible to make. Additionally, the nanoscale is unique because it is the size scale where the familiar day-to-day property of materials like conductivity, hardness, or melting point meet the more exotic properties of the atomic and molecular world such as wave-particle duality and quantum effects. At the nanoscale, the most fundamental properties of materials and machines depend on their size in a way they don't at any other scale. For example, a nanoscale wire or circuit component does not necessarily obey Ohm's law, the venerable equation that is the foundation of modern electronics. Ohm's law relates current, voltage, and resistance, but it depends on the concept of electrons flowing down a wire like water down a river, which they cannot do if a wire is just one atome wide and the electrons need to traverse it one by one. This coupling of size with the most fundamental chemical, electrical, and physical properties of materials is key to all nanoscience.

Nanotechnology should not be confused with its sister field, which is even more of a mouthful -- microelectromechanical systems (MEMS). MEMS scientists and engineers are interested in very small robots with manipulator arms that can do things like flow through the bloodstream, deliver drugs, and repair tissue. These tiny robots could also have a host of other applications including manufacturing, assembling, and repairing larger systems. MEMS is already used in triggering mechanisms for automobile airbags as well as other applications. But while MEMS does have some crossover with nanotechnology, they are by no means the same. For one thing, MEMS is concerned with structures between 1,000 and 1,000,000 nanometers, much bigger than the nanoscale. Further, nanoscience and nanotechnology are concerned with all properties of structures on the nanoscale, whether they are chemical, physical, quantum, or mechanical. It is more diverse and stretches into dozens of subfields. Nanotech is not nanobots.

Nanotechnology has been making its presence felt in industry for some time, and many applications are already standard. Because of the current national debate regarding energy policy and oil, a perfect example may be petroleum refining. Zeolites, the molecular sieves, are now used to extract as much as 40 percent more gasoline from a barrel of crude than the catalysts they replaced. This technique was first developed by Mobil and by some estimates saves approximately 400 million barrels of oil per year (around $12 billion) in the United States alone.

So, what forms of nanotechnology are we most likely to see and touch? Perhaps first on the list of consumer nanogoods are smart materials such as coatings and laminates. Even though you may not put "coatings and laminates" on your grocery list, they are around you everyday. In this case, they are thin layers of various materials that are engineered at the nanoscale to enhance of other products in various ways. For examples, the windows in Audi A4 series cars are coated with glass laminates that block harmful ultraviolet radiation that can cause skin cancer. German and Japanese manufacturers such as Nanogate Technologies have started selling bathroom and kitchen tile that cannot get dirty since it is impossible for dirt and grit particles to cling to the coating in much the same way that food cannot stick to Teflon pans. Slowly, clunky TV-like cathode-ray tubes (CRTs) have been replaced by flat-panel liquid-crystal displays (LCDs). LCDs are more energy efficient, cause less eyestrin, and are more compact than CRTs. But the viewable area of LCDs is typically smaller than that of CRTs (few exceed 24 inches) their images are generally less bright, and they must be viewed directly, not from the side. Also, LCDs tend to refresh the images that they display slowly, which can cause animation and video to look sloppy. Enter light-emitting diode displays.

Citation Source:
Mark A. Ratner & Daniel Ratner. 2003. Nanotechnology: A Gentle Introduction to the Next Big Idea. Prentice Hall Professional.

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