Introduction - Implications of Emerging Micro-and Nanotechnologies - page 6

BOX 1-1
A Matter of Scale

We are used to thinking in a linear world. Changes in scale by many factors of
10 challenge both our intuition and our imagination. In going to the world of micro-
and nanoscale phenomena we move to smaller dimensions by factors of 1,000,
the micrometer being one one-thousandth of a millimeter (the diameter of the tip of
your pen) and the nanometer being a million times smaller than the pen tip, or one
one-thousandth of a micrometer. Figure 1-1-1 shows examples of the impact of the
nanoscale on macroscopic objects for both biological and artificial systems. To
visualize this scale change for everyday objects, consider your morning cup of
coffee. The width of the mug is about 80 millimeters (mm). Now consider the diam-
eter of a human hair, which is typically 50 micrometers (mm), a reduction in scale
by about 1,000. To reach the nanoworld yet another reduction of 1,000 is needed.
An object 50 nanometers (nm) high corresponds to a stack of about 200 atoms. If
packed without space between them, a billion of these nano-objects would fit within
a 50- × 50- × 50-micrometer cube!
The speed of moving objects is another way to visualize large changes in scale.
Consider a baby crawling. A person walking goes about 10 times as fast, a car
traveling at 60 mph is 100 times faster, and a jet fighter at the speed of sound is
1,000 times faster than the crawling baby. Factors of 1,000 in moving between the
macro-, micro-, and nanoworlds are truly large changes that challenge our intuitive
capabilities.

Natural
Organisms

Blood cells
~ 2-5 mm

Hair

~ 50 mm wide

Dog
~ 1 m

Cell membrane

DNA
~2 nm
wide

ATP synthase

1 m

Systems

1 mm

1 µ m

1 nm

Artificial
Systems

Building
Blocks

Functional
subsystems

Material
elements
& circui ts

Devices &
components

Nano particles
& structures

FIGURE 1-1-1 Dimensional scale. SOURCE: Wilson, B. 2001. AFRL Nano Science
and Technology Initiative. Briefing by Barbara Wilson, Chief Technologist, Air
Force Research Laboratory, to the Committee on Implications of Emerging Micro-
and Nanotechnologies, National Academy of Sciences, Irvine, Calif., December 18.