Page 29 - Science at the nanoscale

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June 9, 2009
Chapter Two
Classical Physics
at the Nanoscale
It is often said that “physics is different at the nanoscale”. This
statement cannot be true, since the laws of physics as we know
them today are certainly valid at the nanoscale. Perhaps what is
often meant is that new phenomena or “new physics” are often
observed when we build novel structures, materials and devices
at the nanoscale.
Nevertheless, it is true that at the nanoscale, classical physics
begins to give way to quantum physics in terms of description
of physical phenomena. When we try to describe the properties
of electrons, classical physics fails and we have to use the quan-
tum mechanical wave description of matter to explain the physics
observed. The length scale of electrons is in any case much smaller
than that of atoms and molecules, even though they determine
many materials properties such as conductivity, magnetism and
so on. This subject of quantum physics will be dealt with in the
next chapter.
At the scale of nano- and micro-particles however, we can ch02
adequately describe many physical phenomenon with classical
physics. We often ask questions such as: Why do dust particles
float in the air instead of falling to the ground? Why does a small
drop of water not spread but remain round? Why do micron-sized
wheels have so little inertia? At this scale, the behaviour of objects
is different from what we experience in our daily lives. This is
because at the small scale, forces such as friction and surface ten-
sion often dominate over forces such as gravity.
Science at the Nanoscale: An Introductory Textbook
by Chin Wee Shong, Sow Chorng Haur & Andrew T S Wee
Copyright c
2010 by Pan Stanford Publishing Pte Ltd
www.panstanford.com
978-981-4241-03-8