1
Introduction t
1. Introduction to Nanotechnology
A biological system can be exceedingly small.
Many of the cells are very tiny, but they are
very active; they manufacture various substances;
they walk around; they wiggle; and they do all
kinds of marvelous things—all on a very small
scale. Also, they store information. Consider the
possibility that we too can make a thing very
small that does what we want—that we can
manufacture an object that maneuvers at that
level.
(From the talk “There’s Plenty of Room at the
Bottom,” delivered by Richard P. Feynman at the
annual meeting of the American Physical Society at
1.1 Nanotechnology –
Definition and Examples ....................... 1
1.2 Background and Research Expenditures . 4
1.3 Lessons from Nature (Biomimetics)......... 6
1.4 Applications in Different Fields .............. 7
1.5 Various Issues ...................................... 8
1.6 Research Training................................. 8
1.7 Organization of Handbook .................... 9
References .................................................. 9
the California Institute of Technology, Pasadena,
CA, on December 29, 1959.)
1.1 Nanotechnology – Definition and Examples
Nanotechnology literally means any technology done
on a nanoscale that has applications in the real
world. Nanotechnology encompasses the production
and application of physical, chemical, and biological
systems at scales ranging from individual atoms or
molecules to submicron dimensions, as well as the
integration of the resulting nanostructures into larger
systems. Nanotechnology is likely to have a profound
impact on our economy and society in the
early 21st century, comparable to that of semiconductor
technology, information technology, or cellular and
molecular biology. Science and technology research
in nanotechnology promises breakthroughs in areas
such as materials and manufacturing, nanoelectronics,
medicine and healthcare, energy, biotechnology, information
technology, and national security. It is widely
felt that nanotechnology will be the next industrial
revolution.
Nanometer-scale features are mainly built up from
their elemental constituents. Examples include chemical
synthesis, the spontaneous self-assembly of molecular
clusters (molecular self-assembly) from simple reagents
in solution, biological molecules (e.g., DNA) used as
building blocks for the production of three-dimensional
nanostructures, or quantum dots (nanocrystals) of arbitrary
diameter (about 10 to 105 atoms). The definition of
a nanoparticle is an aggregate of atoms bonded together
with a radius between 1 and 100 nm. It typically consists
of 10 to 105 atoms. A variety of vacuum deposition and
nonequilibrium plasma chemistry techniques are used to
produce layered nanocomposites and nanotubes. Atomically
controlled structures are produced using molecular
beam epitaxy and organometallic vapor phase epitaxy.
Micro- and nanosystem components are fabricated using
top-down lithographic and nonlithographic fabrication
techniques and range in size from micro- to nanometers.
Continued improvements in lithography for use in
the production of nanocomponents have resulted in line
widths as small as 10 nm in experimental prototypes.
The nanotechnology field, in addition to fabrication of
nanosystems, provides impetus to develop experimental
and computational tools.
The discovery of novel materials, processes, and
phenomena at the nanoscale and the development of new
experimental and theoretical techniques for research
provide fresh opportunities for the development of innovative
nanosystems and nanostructured materials. The
properties of materials at the nanoscale can be very different
from those at a larger scale. When the dimension
of a material is reduced from a large size, the properties
remain the same at first, then small changes occur, until
finally, when the size drops below 100 nm, dramatic
Introduction
2 Part Introduction
Size (nm)
0.1 1 10 100 1000 10 000 100 000
Human hair
50–100µm
DMD 12 µm
Red blood cell
8µm
Quantum-dot transistor
300 nm
Drain
Molecular gear
10 nm–100 nm
DNA 2.5nmC atom 0.16 nm
Yoke
Landing
tip
MEMS: Characteristic length less than 1mm,
larger than 100 nm
NEMS: Less than 100 nm
SWCNT transistor
15 nm
Fig. 1.1 Dimensions of MEMS and NEMS in perspective. MEMS/NEMS examples shown are of a vertical singlewalled
carbon nanotube (SWCNT) transistor (5 nm wide and 15 nm high) [1.1], of molecular dynamic simulations of
a carbon-nanotube-based gear [1.2], quantum-dot transistor obtained from [1.3], and DMD obtained from www.dlp.com
changes in properties can occur. If only one length of
a three-dimensional nanostructure is of nanodimension,
the structure is referred to as a quantum well; if two sides
are of nanometer length, the structure is referred to as
a quantum wire. A quantum dot has all three dimensions
in the nanorange. The word quantum is associated with
these three types of nanostructures because changes in
properties arise from the quantum-mechanical nature of
physics in the domain of the ultra small. Materials can
be nanostructured for new properties and novel performance.
This field is opening new venues in science and
technology.
Micro- and nanosystems include micro/nanoelectromechanical
systems. MEMS refers to microscopic
devices that have a characteristic length of less than
1 mm but more than 100 nm and combine electrical
and mechanical components. NEMS refers to
nanoscopic devices that have a characteristic length
of less than 100 nm and combine electrical and mechanical
components. In mesoscale devices, if the
functional components are on a micro- or nanoscale,
they may be referred to as MEMS or NEMS,
respectively. These are referred to as intelligent
miniaturized systems comprising sensing, processing,
and/or actuating functions and combine electrical
and mechanical components. The acronym MEMS
originated in the USA. The term commonly used
in Europe is microsystem technology (MST), and
in Japan it is micromachines. Another term generally
used is micro/nanodevices. MEMS/NEMS terms
are also now used in a broad sense and include
electrical, mechanical, fluidic, optical, and/or biological
functions. MEMS/NEMS for optical applications
are referred to as micro/nanooptoelectromechanical
systems (MOEMS/NOEMS). MEMS/NEMS for electronic
applications are referred to as radio-
Introduction
Introduction to Nanotechnology 1.1 Nanotechnology – Definition and Examples 3
Table 1.1 Dimensions and masses in perspective. (a) Dimensions
in perspective
NEMS characteristic < 100 nm
length
MEMS characteristic length 1 mm and > 100 nm
Molecular gear ≈ 10 nm
Vertical SWCNT transistor ≈ 15 nm
Quantum-dots transistor 300 nm
Digital Micromirror 12 000 nm
Individual atoms Typically fraction
of a nm in diameter
DNA molecules ≈ 2.5 nm wide
Biological cells In the range of thousands
of nm in diameter
Human hair ≈ 75 000 nm in diameter
Table 1.2 (cont.) (b) Masses in perspective
NEMS built with cross As low as 10−20 N
sections of about 10 nm
Micromachines silicon As low as 1 nN
structure
Water droplet ≈ 10 µN
Eyelash ≈ 100 nN
frequency-MEMS/NEMS or RF-MEMS/RF-NEMS.
MEMS/NEMS for biological applications are referred
to as BioMEMS/BioNEMS.
To put the dimensions of MEMS and NEMS in perspective,
see Fig. 1.1 and Table 1.1. Individual atoms are
typically a fraction of a nanometer in diameter, DNA
molecules are about 2.5 nm wide, biological cells are in
the rage of thousands of nanometers in diameter, and
human hair is about 75 µm in diameter. The NEMS
shown in the figure range in size from 15 to 300 nm
and MEMS is 12 000 nm. The mass of a micromachined
silicon structure can be as low as 1 nN, and NEMS can
be built with a mass as low as 10−20 N with cross sections
of about 10 nm. In comparison, the mass of a drop
of water is about 10 µN, and the mass of an eyelash is
about 100 nN.
MEMS and emerging NEMS are expected to
have a major impact on our lives, comparable to
that of semiconductor technology, information technology,
or cellular and molecular biology [1.4, 5].
MEMS/NEMS are used in electromechanical, electronics,
information/communication, chemical, and
biological applications. The MEMS industry in 2004
was worth about $4.5 billion and with a projected annual
growth rate of 17% (Fig. 1.2) [1.6]. Growth of Si-based
8
7
6
5
4
3
2
1
0
20072006200520042003
30
20
10
0
2008200720062005200420032002
US $ (billions)
year
a) Global MEMS market segment
Microbolometers
RF MEMS
Bio & Microfluidics comp.
DLP (micromirrors)
MOEMS
Gyroscopes
Accelerometers
Pressure sensors
Inkjet head
year
US $ (billions)
b) Global nanotechnology market segment
Nanodevices
Nanotools
Nanomaterials
Fig. 1.2 Global MEMS and nanotechnology market seg-
ments
MEMS may slow down, and nonsilicon MEMS may
pick up during the next decade. The NEMS industry
was worth about $10 billion dollars in 2004, mostly in
nanomaterials (Fig. 1.2) [1.7]. It is expected to expand
in this decade, in nanomaterials, biomedical applications,
and nanoelectronics or molecular electronics. For
example, miniaturized diagnostics could be implanted
for early diagnosis of illness. Targeted drug delivery devices
are under development. Due to the enabling nature
of these systems and because of the significant impact
they can have on both commercial and defense applications,
industry as well as federal governments have taken
a special interest in seeing growth nurtured in this field.
MEMS/NEMS are the next logical step in the “silicon
revolution.”
Introduction
4 Part Introduction
1.2 Background and Research Expenditures
On December 29, 1959 at the California Institute of
Technology, Nobel Laureate Richard P. Feynman gave a
talk at the annual meeting of the American Physical Society
that has become a classic in 20th-century science
lectures. The talk was titled “There’s Plenty of Room at
theBottom”[1.8]. Hepresented atechnological vision of
extreme miniaturization in 1959, several years before the
word “chip” became part of the lexicon. He talked about
the problem of manipulating and controlling things on
a small scale. Extrapolating from known physical laws,
Feynman envisioned a technology using the ultimate
toolbox of nature, building nanoobjects atom by atom or
molecule by molecule. Since the 1980s, many inventions
and discoveries in the fabrication of nanoobjects have
4
3
2
1
0
200220012000199919981997 2003
3
2
1
0
R&D expenditure (US $ billions)
a) Public expenditure in nanotechnology R&D
R&D expenditure (US $ billions)
b) Public and private expenditure in nanotechnology R&D
in 2004
NNI
(USA)
FP6
(EU)
Europe USA Japan Others
EC 0.48
Member
states +
associated
1.40
Private
1.30
Private
1.70
Private
1.40
Public
1.90
Public
0.90
States
0.40
Federal
0.99
Europe
USA
Others
Japan
Fig. 1.3a,b Breakdown of public expenditure in nanotechnology
R&D (a) around the world (source: European
Commission 2003) and (b) by public and private resources
in 2004 (source: European Commission 2005; private figures
based upon Lux Research)
been testament to his vision. In recognition of this reality,
in 1998 the White House National Science and Technology
Council (NSTC) created the Interagency Working
Group on Nanoscience, Engineering, and Technology
(IWGN). In a January 2000 speech at the same institute,
former President Bill Clinton talked about the exciting
promise of “nanotechnology” and, more broadly,
the importance of expanding research in nanoscale science
and technology. Later that month, he announced
in his State of the Union Address an ambitious $497
million federal, multiagency national nanotechnology
initiative (NNI) in the 2001 fiscal year budget and made
the NNI a top science and technology priority [1.9,10].
The objective of this initiative was to form a broad-based
coalition in which academia, the private sector, and local,
state, and federal governments would work together to
push the envelope of nanoscience and nanoengineering
to reap nanotechnology’s potential social and economic
benefits.
Funding for this initiative in the US has continued
to rise. In January 2003, the US Senate introduced a bill
to establish a National Nanotechnology Program. On
4
3
2
1
0
Japan
U
SAG
erm
any
U
K
Taiw
an
South
K
oreaA
ustralia
China
France
Italy
R&D expenditure (US $ billions)
Public and private expenditure in nanotechnology R&D in 2004
Government/institutional
Corporate/private
2004 global total
Corporate/private – $ 6.6 billion
Government/institutional – $ 3.7 billion
Fig. 1.4 Breakdown of public and private expenditures
in nanotechnology R&D in 2004 in various countries
(Lawrence 2005)
Introduction
Introduction to Nanotechnology 1.2 Background and Research Expenditures 5
a) Worldwide publications
in nanotechnology
(1997–1999)
Others
5%
Candidate
countries
and Russia
8%
Europe
34%
USA and
Canada
28%
Asia
25%
b) Worldwide patents
in nanotechnology
Others
3%
Europe
39%
USA and
Canada
45%
Asia
13%
Fig. 1.5a,b Breakdown of (a) worldwide publications and
(b) worldwide patents (source: European Commission
2003)
December 3, 2003, President George W. Bush signed
into law the 21st Century Nanotechnology Research and
Development Act. The legislation put into law programs
and activities supported by the National NanotechnologyInitiative.
Thebillgavenanotechnologyapermanent
home in the federal government and authorized $3.7
billion to be spent in the 4-year period beginning in
October 2005 on nanotechnology initiatives at five
federal agencies. The funds would provide grants to
researchers, coordinate R&D across five federal agencies
[National Science Foundation (NSF), Department
ofEnergy(DOE),NASA,NationalInstituteofStandards
and Technology (NIST), and Environmental Protection
Agency (EPA)], establish interdisciplinary research centers,
and accelerate technology transfer into the private
sector. In addition, the departments of Defense (DOD),
Homeland Security, Agriculture, and Justice, as well as
the National Institutes of Health (NIH), also fund large
R&D activities. They currently account for more than
one third of the federal nanotechnology budget.
The European Union (EU) made nanosciences and
nanotechnologies a priority in the Sixth Framework Program
(FP6) in 2002 for the period 2003–2006. They
had dedicated modest funds in FP4 and FP5. FP6 was
Start-up companies
in nanotechnology
(1997–2002)
Asia
4%
Rest of
World
11%
Switzerland
4%
Others
5%
USA
55%
Europe
29%
Germany
11%
UK
6%
France
4%
Fig. 1.6 Breakdown of startup companies around the world
(1997–2002) (source: CEA, Bureau d’Etude Marketing)
tailored to better help structure European research and
to cope with the strategic objectives set out in Lisbon
in 2000. Japan identified nanotechnology as one of its
main research priorities in 2001. The funding levels increased
sharply from $400 million in 2001 to around
$950 million in 2004. In 2003, South Korea embarked
on a 10-year program with around $2 billion of public
funding, and Taiwan has committed around $600 million
of public funding over 6 years. Singapore and China
are also investing on a large scale. Russia is well funded
as well.
Figure 1.3a shows the public expenditure breakdown
in nanotechnology R&D around the world, with
about US$5 billion in 2004, being about equal by USA,
Japan, and Europe. Next we compare public expenditure
on a per-capita basis. The average expenditures
per capita for the US, EU-25, and Japan were about
$3.7, $2.4, and $6.2, respectively [1.11]. Figure 1.3b
shows the breakdown of expenditures in 2004 by public
and private sources with more than $10 billion spent on
nanotechnology research. Two thirds of this came from
corporate and private funding. The private expenditure
in the United States and Japan was slightly larger than
that of the public, whereas in Europe it was about one
third. Figure 1.4 shows the public and private expenditure
breakdown in 2004 in various countries. Japan
Introduction
6 Part Introduction
and the US had the largest expenditure, followed by
Germany, Taiwan, South Korea, UK, Australia, China,
France, and Italy. Figure 1.5 shows the breakdown of
worldwide publications and patents. The US and Canada
led, followed by Europe and Asia. Figure 1.6 shows
the breakdown in startup companies around the world
(1997–2002). Entrepreneurship in the USA is clearly
evident followed by Europe.
1.3 Lessons from Nature (Biomimetics)
Nanotechnology is a new word, but it is not an entirely
new field. Nature has many objects and processes that
function on a micro- to nanoscale [1.9,12]. The understanding
of these functions can guide us to imitate and
produce nanodevices and nanomaterials. Abstractions of
good design from nature are referred to as biomimetics.
Billions of years ago, molecules began organizing
into the complex structures that could support life.
Photosynthesis harnesses solar energy to support plant
life. Molecular ensembles present in plants, which include
light-harvesting molecules such as chlorophyll
arranged within the cells on the nanometer to micrometer
scales, capture light energy and convert it into the
chemical energy that drives the biochemical machinery
of plant cells. Live organs use chemical energy in the
body. The flagellum, a type of bacteria, rotates at over
10 000 RPM [1.13]. This is an example of a biological
molecular machine. The flagellum motor is driven by
the proton flow caused by the electrochemical potential
differences across the membrane. The diameter of the
bearing is about 20–30 nm with an estimated clearance
of about 1 nm.
In the context of tribology, some biological systems
have antiadhesion surfaces. First, many plant leaves
(such as the lotus leaf) are covered by a hydrophobic
cuticle, which is composed of a mixture of large
hydrocarbon molecules that have a strong aversion to
water. Second, the surface has a unique roughness distribution
[1.14, 15]. It has been reported that for some
leaf surfaces, the roughness of the hydrophobic leaf surface
decreases wettability, which is reflected in a greater
contact angle of water droplets on such surfaces.
“Geckos” (a family of lizards) are known for their
amazing climbing ability. They can run up any wall, run
across the ceiling, and stick to ceilings. They rely on the
extreme miniaturization and multiplication of contact
elements. Soles of geckos are covered with about half
a million submicrometer keratin hairs, called spatulae,
which are what make their feet, known as “gecko feet”,
so sticky. Each hair is 30–130 µm long and is only one
tenth the diameter of a human hair and contains hundreds
of projections terminating in 0.2–0.5 µm spatula-shaped
structures. The foot typically has about 5000 hair/mm2.
Each hair produces a tiny force (≈ 100 nN), primarily
due to van der Waals attraction, and possibly capillary
interactions (meniscus contribution), and millions
of hairs acting together create a large adhesive force
on the order of 10 N with a pad area of approximately
100 mm2 [1.16], sufficient to keep geckos firmly on
their feet, even when upside down on a glass ceiling.
The bonds between hair and a surface can be easily
broken by “peeling,” in the same way one removes
a strip of adhesive tape, allowing geckos to run across
ceilings.
Spiders, a family of anthropods (spiders, insects, and
crustaceans) can stick to smooth, overhanging surfaces
also because of a large number of hairs and the microstructure
of the hairs on their feet. Spiders use claws
to attach to rough surfaces but have scopulae (tufts of
hairs) on their feet to adhere to smooth surfaces. The
scopulae hairs of the jumping spider, Evarcha arcuata,
branch into a very large number of smaller hairs
or setulae, whose broadened ends have a contact area
of about 2×105 nm2 [1.17]. The number of setulae per
foot is about 80, 000 giving a total of about 7 00, 000
contact points for the spider’s eight legs [1.17]. This
provides a large amount of adhesive force because of
van der Waals attraction added on all legs. The hair
surface (cuticle) is sealed with a topographically microconfigured
wax layer. These surfaces are reportedly
nonwettable, so capillary interactions are not expected
to be significant.
Scientists are attempting to create a new type of
adhesive tape by mimicking the structure of gecko or
spider feet. Geim et al. [1.18] reported the fabrication
of a “gecko” tape made by microfabrication of dense
arrays of flexible plastic pillars that are little more than
2 µm tall with a pitch on a similar scale.
Introduction
Introduction to Nanotechnology 1.4 Applications in Different Fields 7
1.4 Applications in Different Fields
Science and technology continue to move forward in
making the fabrication of micro/nanodevices and systems
possible for a variety of industrial, consumer, and
biomedical applications (see, e.g., [1.19, 20]). A variety
of MEMS devices have been produced, and some
are commercially used [1.12, 21–29]. Several types of
sensors are used in industrial, consumer, defense, and
biomedical applications. Various micro/nanostructures
or micro/nanocomponents are used in microinstruments
and other industrial applications such as micromirror
arrays. The largest “killer” MEMS applications include
accelerometers (some 90 million units installed
in vehicles in 2004), silicon-based piezoresistive pressure
sensors for manifold absolute pressure sensing
for engines and for disposable blood pressure sensors
(about 30 million units and about 25 million units,
respectively), capacitive pressure sensors for tire pressure
measurements (about 37 million units in 2005),
thermal inkjet printheads (about 500 million units in
2004), and digital micromirror arrays (about $700 million
in revenue in 2004). Other applications of MEMS
devices include chemical/biosensors and gas sensors,
microresonators, infrared detectors, and focal plane arrays
for earth observations, space science, and missile
defense applications, picosatellites for space applications,
fuel cells, and many hydraulic, pneumatic, and
other consumer products. MEMS devices are also being
explored for use in magnetic storage systems
(Bhushan [1.30]), where they are being developed for
supercompact and ultrahigh-recording-density magnetic
disk drives.
NEMS are produced by nanomachining in a typical
top-down and bottom-up approach, largely relying
on nanochemistry [1.31–37]. Examples of NEMS include
microcantilevers with integrated sharp nanotips
for scanning tunneling microscopy (STM) and atomic
force microscopy (AFM), quantum corral formed using
STM by placing atoms one by one, AFM cantilever
array (Millipede) for data storage, AFM tips for nanolithography,
dip-pen lithography for printing molecules,
nanowires, carbon nanotubes, quantum wires, quantum
boxes, quantum-dot transistors, nanotube-based sensors,
biological (DNA) motors, molecular gears by attaching
benzene molecules to the outer walls of carbon nanotubes,
devices incorporating nanometer-thick films (e.g.,
in giant magnetoresistive or GMR read/write magnetic
heads and magneticmedia) for magneticrigid disk drives
and magnetic tape drives, nanopatterned magnetic rigid
disks, and nanoparticles (e.g., nanoparticles in magnetic
tape substrates and magnetic particles in magnetic tape
coatings).
Nanoelectronics can be used to build computer memory
using individual molecules or nanotubes to store bits
of information, molecular switches, molecular or nanotube
transistors, nanotube flat-panel displays, nanotube
integrated circuits, fast logic gates, switches, nanoscopic
lasers, and nanotubes as electrodes in fuel cells.
BioMEMS/BioNEMS are increasingly used in commercial
and defense applications; see, e.g., [1.38–44].
They are used for chemical and biochemical analyses
(biosensors) in medical diagnostics (e.g., DNA, RNA,
proteins, cells, blood pressure and assays, and toxin
identification) [1.44,45], tissue engineering [1.46], and
implantable pharmaceutical drug delivery [1.47, 48].
Biosensors, also referred to as biochips, deal with liquids
and gases. There are two types. A large variety of biosensors
are based on micro/nanofluidics. Micro/nanofluidic
devices offer the ability to work with smaller reagent
volumes and shorter reaction times, and perform analyses
multiple times at once. The second type of biosensors
includes micro/nanoarrays that perform one type of analysis
thousands of times. Micro/nanoarrays are a tool
used in biotechnology research to analyze DNA or proteins
to diagnose diseases or discover new drugs. Also
called DNA arrays, they can identify thousands of genes
simultaneously [1.41]. They include a microarray of silicon
nanowires, roughly a few nanometers in size, to
selectively bind and detect even a single biological molecule,
such as DNA or protein, using nanoelectronics to
detect the slight electrical charge caused by such binding,
or a microarray of carbon nanotubes to electrically
detect glucose.
After the tragedy of September 11, 2001, concern
over biological and chemical warfare has led to the development
of handheld units with bio- and chemical
sensors for the detection of biological germs, chemical
or nerve agents, and mustard agents and to chemical precursors
to protect subways, airports, water supply, and
the population at large [1.49].
BioMEMS/BioNEMS are also being developed
for minimal invasive surgery including endoscopic
surgery, laser angioplasty, and microscopic surgery.
Other applications include implantable drug-delivery
devices—micro/nanoparticles with drug molecules encapsulated
in functionalized shells for site-specific
targeting applications and a silicon capsule with
a nanoporous membrane filled with drugs for long-term
delivery.
Introduction
8 Part Introduction
1.5 Various Issues
There is an increasing need for a multidisciplinary,
system-oriented approach to the manufacture of micro/nanodevices
that function reliably. This can only
be achieved through the cross-fertilization of ideas from
different disciplines and the systematic flow of information
and people among research groups. Common
potential failure mechanisms for MEMS/NEMS requiring
relative motion that need to be addressed in order
to increase their reliability are adhesion, friction, wear,
fracture, fatigue, and contamination [1.50–53]. Surface
micro/nanomachined structures often include smooth
and chemically active surfaces. Due to a large surface
area to volume ratio in MEMS/NEMS, they are particularly
prone to stiction (high static friction) as part
of normal operation. Fracture occurs when the load on
a microdevice is greater than the strength of the material.
Fracture is a serious reliability concern, particularly for
brittle materials used in the construction of these components,
since it can immediately or would eventually
lead to catastrophic failures. Additionally, debris can be
formed from the fracturing of microstructures, leading
to other failure processes. For less brittle materials, repeated
loading over a long period of time causes fatigue
that would also lead to the breaking and fracturing of the
device. In principle, this failure mode is relatively easy
to observe and simple to predict. However, the material
properties of thin films are often not known, making
fatigue predictions error prone.
Many MEMS/NEMS devices operate near their thermal
dissipation limit. They may encounter hot spots that
may cause failures, particularly in weak structures, such
as diaphragms or cantilevers. Thermal stressing and relaxation
caused by thermal variations can create material
delamination and fatigue in cantilevers. In large temperature
changes, as experienced in outer space, bimetallic
beams will also experience warping due to mismatched
coefficients of thermal expansion. Packaging has been
a big problem. The contamination, which probably happens
in packaging and during storage, also can strongly
influence the reliability of MEMS/NEMS. For example,
a particulate dust that lands on one of the electrodes of
a comb drive can cause catastrophic failure. There are
no MEMS/NEMS fabrication standards, which makes it
difficult to transfer fabrication steps in MEMS/NEMS
between foundaries.
Obviously, studies of determination and suppression
of active failure mechanisms affecting this new and
promising technology are critical to a high reliability of
MEMS/NEMS and are determining factors in successful
practical application.
Adhesion between a biological molecular layer and
the substrate, referred to as “bioadhesion,” and reduction
of friction and wear of biological layers, biocompatibility,
and biofouling for BioMEMS/BioNEMS are
important.
Mechanical properties are known to exhibit a dependence
on specimen size. Mechanical property evaluation
of nanometer-scaled structures is carried out to help
design reliable systems since good mechanical properties
are of critical importance in such applications.
Some of the properties of interest are Young’s modulus
of elasticity, hardness, bending strength, fracture
toughness, and fatigue life. Finite element modeling is
carried out to study the effects of surface roughness and
scratches on stresses in nanostructures. When nanostructures
are smaller than a fundamental physical length
scale, conventional theory may no longer apply, and
new phenomena emerge. Molecular mechanics is used
to simulate the behavior of a nanoobject.
The societal, ethical, political, and health/safety implications
are receiving considerable attention [1.11].
One of the prime reasons is to avoid some of the public
skepticism that surrounded the debate over biotech
advances such as genetically modified foods, while at
the same time dispelling some of the misconceptions
the public may already have about nanotechnology.
Health/safety issues need to be addressed as well. For example,
onekey question is what happens to nanoparticles
(such as buckyballs or nanotubes) in the environment
and whether they are toxic in the human body if ingested.
1.6 Research Training
With a decreasing number of people in western countries
going into science and engineering and with the
rapid progress being made in nanoscience and nanotechnology,
the problem of a trained work force is
expected to be acute. Education and training is essential
to produce a new generation of scientists, engineers,
and skilled workers with the flexible and interdisciplinary
R&D approach necessary for rapid progress
in nanosciences and nanotechnology [1.54]. The question
is being asked: Is the traditional separation of
Introduction
Introduction to Nanotechnology References 9
academic disciplines into physics, chemistry, biology,
and various engineering disciplines meaningful at the
nano level? Generic skills and entrepreneurship are
needed to translate scientific knowledge into products.
Scientists and engineers in cooperation with relevant experts
should address the societal, ethical, political, and
health/safety implications of their work for society at
large.
To increase the pool of students interested in science
and technology, science needs to be projected as exciting
at the high school level. Interdisciplinary curricula
relevant for nanoscience and nanotechnology need to
be developed. This requires revamping the education,
developing new courses and course materials including
textbooks [1.28,36,53,55–57] and instruction manuals,
and training new instructors.
1.7 Organization of Handbook
The handbook integrates knowledge from the point of
view of fabrication, mechanics, materials science, and
reliability. Organization of the book is straightforward.
The handbook is divided into eight parts. The first
part of the book includes an introduction to nanostructures,
micro/nanofabrication, methods, and materials.
The second part introduces various MEMS/NEMS and
BioMEMS/BioNEMS devices. The third part introduces
scanning probe microscopy. The fourth part provides an
overview of nanotribology and nanomechanics, which
will prepare the reader for understanding the tribology
and mechanics of industrial applications. The fifth
part provides an overview of molecularly thick films for
lubrication. The sixth part focuses on industrial applications,
and the seventh part focuses on microdevice
reliability. Finally, the last part focuses on technological
convergence from the nanoscale as well as the social,
ethical, and political implications of nanotechnology.
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Introduction