Over
the past twenty years, the science and engineering of nanomechanical systems
(NEMS) has developed into a quite extended and rapidly growing area of research.
The first examples of such mechanical systems, advanced by the application of
semiconductor lithographic techniques to the fabrication of mechanically active
devices, included cantilevers where the application of a force as small as a few
piconewtons would cause measurable displacements, and structures fabricated with
size scales such that the fundamental mechanical mode was in the 100 MHz band.
Extensive efforts exploring different materials and methods to support these
structures has supported the advent of very high quality factor mechanical
resonators with frequencies ranging from the MHz band well into the GHz band of
frequencies. This has allowed the development of nanomechanical resonators as
time-keeping systems competitive with macroscale quartz crystals; as
radiofrequency filters for the cellphone industry; and increasingly as systems
with strong potential for fundamental experiments in quantum mechanics as well
as applications to quantum information technology. Nanomechanical systems also
are playing an increasingly important and central role as ultrasensitive
detectors of mass, displacement, acceleration, force or spin. The applications
that have become possible include measurements of forces between individual
biomolecules, forces originating in the magnetic resonant response of single
electron and nuclear spins, and noise that arises from mass fluctuations
involving single molecules. As a result, this area of research attracts a large
number of researchers from around the world. By their nature, nanomechanical
systems are interdisciplinary, since they can couple to electrical circuits or
optical cavities and they have potential applications in sensing,
telecommunications, biophysics, and photonics, topics which are studied not only
in condensed matter but also in the applied physics.