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Comparison:
Grain
of Beach Sand
500 micrometers
Pollen
Grains
25 to 50 micrometers
Wavelength
of visible light 500 nanometers = 0.5
micrometers
Ribosome
25 nanometers = 0.025 micrometers
Atoms
~0.1 nanometer = 0.0001micrometers |
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Assembler
"A
general-purpose device for molecular manufacturing capable of guiding
chemical reactions by positioning molecules" (Drexler,
293) This device would be like a nano-scale manufacturing plant,
taking in simple raw materials and individually placing atoms to build up a
more complex structure. It would have to be somehow programmed before
hand.
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Bottom Up vs. Top Down
The established approach has forever been to whittle down a chunk
of material down to a desired size or shape, and this is referred to as
the “Top-Down” approach. Just
like cast iron objects and carved wooden tools are produced on a
human-sized scale, the same processes are used on the micro scale.
A laser is focused to a very tight beam and burns away the material
in a very limited area. more commonly referred to as micro machining.
There are others who have devised a “Bottom-Up” approach
instead. This involves the
individual manipulation of atoms or molecules in order to move them into
position. Atoms are places in a
predefined order and as they are placed they bond together to form some
structure. This method is often what is implied when speaking of
"Nanotechnology" because top-down approaches are not viable
options at the atomic scale. This is also much different than
the genetic approaches which involve chemical baths. Rather than
relying on the self-assembly of chemistry or biology, experimenters in
this area visually look at where the atom is going when they place it.
The first example of this was in 1989 when scientists for IBM
placed 35 individual xenon atoms to form the letters “IBM."
(Regis,
11)
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Electron
Microscope
"An electron-optical
instrument in which a beam of electrons focused by means of an electron
lens is used to produce an enlarged image of a minute object on a
fluorescent screen or photographic plate." (Webster's)
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Fabrication
"The act or process
of constructing from diverse and usually standardized parts." (Webster's)
Fabrication is the manufacturing of components, in this case on the
molecular scale.
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Lithography
A thin
layer of the desired material is coated onto a surface that can later be
eaten away from the back. A beam of particles or light is then
precisely projected onto the layer and burns away certain portions of
it. With more complex devices more steps are included but in general
lithography is the etching of a surface to produce a desired pattern.
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Macro-scale vs. Micro-scale:
When
comparing Nanotechnology and it's applications to the Real World, the
prefixes micro and micro are often used. As in economics, these
refer to the big picture (macro) and the individual (micro). Things
that we can see and touch, such as paper, books, clothing, etc., are seen
in the macro perspective and often apply to the point where nanotechnology
might someday be used to create household products. Micro in this
comparison is not used strictly as a term of magnitude such as a
micrometer, but simply to refer to those things that cannot be seen with
the human eye. |
STM
& AFM
A Scanning Tunneling Microscope
(STM) is a device used to view atoms by moving a very precise tip over the
surface of an object. The device measures the distance between the
tip and the surface by measuring the current that is jumping the gap
between the two. As the tip is moved along the differences in this
current can be mapped and used as a representation of what the surface
looks like.
An Atomic Force Microscope (AFM)
actually touches the surface of the object. As it is dragged along
the surface of the object, directional sensors measure movements of the
tip in the XY and Z directions. These movements are then used to map
out the atoms on the surface. (Drexler, 93) |
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