Science entered the twentieth century with newfound knowledge that our world is composed of fundamental building blocks, atoms and molecules, that are extremely small--approximately a nanometer in any dimension. (The prefix "nano," meaning one-billionth, comes from the Greek word nanos, meaning dwarf) As the twenty-first century begins, science has begun to manipulate these building blocks one at a time, on the brink of constructing nano-sized machines and components that can make many products lighter, stronger, smarter, cheaper, cleaner, and more precise. This new field is called nanotechnology, a word coined by engineer K. Eric Drexler in 1981.
The invention of the scanning probe microscope (SPM)opened a new window into the molecular and atomic realm. With it comes the ability to view individual molecules and atoms, and in some cases to watch their progression as a system evolves. Now that they can be viewed, nanotechnology seeks to take the next step and manipulate these nano-particles, building tools and other constructions from the bottom up.
Researchers at AT&T Bell Laboratories carved a few early microdevices out of silicon in 1987, and in 1991 "carbon nanotubes" were first created by Sumio Iijima of the NEC Corporation. Based on the 1985 discovery of buckminsterfullerene, a new form of carbon labeled C60, nanotubes are tiny tubes consisting of rolled up carbon hexagons. They are 10,000 times smaller than a human hair, and have potential use as minuscule wires, in ultrasmall electronic devices, and as tiny sensors. In the future nanotechnologists hope to make nano-machines consisting of only a few thousand atoms. Such materials, prepared one building block at a time, could possess unusual properties such as superstrength.
How to build such devices? An SPM could change a surface, depositing individual atoms and molecules in a desired pattern, for example. Scientists have used this technique to form patterns, in one case the letters of their employer, IBM. However, such SPMs need to be cooled to very low temperatures to accomplish such feats, only a few degrees Kelvin, and are still far too slow to construct sizeable objects.
Nanotechnologists believe they may be able to work around this problem in several ways. One is to use large molecules as the building blocks of the nanomachines, thus requiring fewer trips back to the brickpile, if you will. Another is self-assembly, where the building blocks come together without human intervention to form an ordered system, billions at a time. This is not unprecedented--cells, for example, contain all the information they need to assemble themselves. Long chains of amino acids twist and turn back onto themselves to form three-dimensional proteins. The atoms in steel rearrange as it is heated or cooled, changing its strength and flexibility. Researchers hope to learn from such processes, and to zero in on building blocks that are "sticky"--that fit together naturally due to their individual electric charges, their shapes, or other qualities. Diamond might become a building material, since it has over 50 times the strength-to-weight ratio of steel.
Nanoscale equivalents of "arms" and "hands" need to be developed. Current proposals for molecular-scale positional devices resemble normal-sized robotic devices, but are about one ten-millionth as big. A robotic arm, for example, might be composed of a few million atoms, be about 100 nm long and 30 around. Trillions of such devices could occupy a few cubic millimeters, a speck slightly larger than a pinhole.
Such robotic arms could be used to create other robots, such as tiny surgical robots to repair the body from the inside out, or seek-out and destroy a virus. Or they may make more traditional machines, but on a nano-scale: gears, shafts, bearings, belts, motors, and improved circuitry for digital logic. Chemist George Whitesides and colleagues have already succeeded in finding a way to create microscopic molds from which thousands of computer chips or other miniature components may be cast.
Nanotechnology is still a few decades off, scientist say, but they believe they have the basic knowledge, understanding, and tools to bring it about. In other words, they believe the advancement of nanotechnology is now a matter of engineering, and no longer science.
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