|
Items in cart [0] |
Questions? Call 888-624-8373 |
|
||||||||||||||||
|
||||||||||||||||
|
|
|||||||||||||||
| ||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 13
The Role of Materials in Future Industries
Session Chair—Lee Magid, University of Tennessee, Knoxville
Nanomaterials, Julia Weertman, Northwestern University
Biomaterials, David Tirrell, California Institute of Technology
Optical Materials, Rod Alferness, Lucent Technologies
Computational Materials Science, Sharon GIotzer, University of Michigan
1
Progress in industry and manufacturing and the nationls economic health rely on
the continual discovery, development, and use of new materials for new products. Some
of today's most exciting and groundbreaking science is focused on nanomaterials,
biomaterials, and materials for optical communications. As in all areas of cutting-edge
research, computation is playing an increasingly central role in the development and
understanding of materials systems.
NANOMATERIALS
Nanomaterials are a relatively newly recognized class of materials. They were
defined in this workshop as any material having at least one dimension less than 100
nanometers. While some naturally nanostructured materials are in use in commercial
applications, artificially manufactured nanomaterials have demonstrated some
particularly interesting and promising properties. Some examples of nanomaterial
structures are shown in Figure 3-~.
Nanolayer materials, such as those composed of thin layers of copper and nickel,
can be much stronger and harder than either of the two components alone. This
strengthening results from the disruption of some of the stress relief mechanisms in the
crystalline structure. Layered materials can also exhibit a high resistance to corrosion,
and there is evidence that the use of nanolayers can improve the fatigue life of
~~_~ ITS 1 ~ 1 _ · ~ , . -
~;~1~1~. ~~ano~ayerea semiconductor materials are being used to produce efficient
electronic and optoelectronic devices such as diode lasers.
Nanoparticle materials are attractive for nanoabrasive polishing, for highly
targeted drug delivery, and even for cosmetics such as sun block. Nanohole materials
find application as molecular sieves and nanograined materials, i.e., small-grain-size,
three-dimensional materials that exhibit significant increases in strength.
Nanotube materials consist of sheets of carbon atoms seamIessly wrapped in
cylinders only a few nanometers in diameter but up to a millimeter long. The number of
both specialized and large-scale applications of nanotubes is ~rc~win~ const~ntiv Their
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ is _ _ 1 1 ~ 1 1 , 1
plopcl~l~b Ud11 UC COllLI-OllCU Dy changing Ine orientation of the carbon sheet. Nanotubes
13
OCR for page 14
MATERIALS AND SOCIETY
can be macie to be semiconclucting or
conducting ant] have been user! to
strengthen polymers. They can also be
used as tips or probes for microscopy.
Nanomaterials show great
promise in new applications and new
manufacturing processes, but many
problems ant] challenges remain. The
development and application of
nanomaterials will neec! techniques to
produce powders of high quality in
sufficient quantities and at a low enough
cost to improve the low fracture
toughness and poor ductility of three-
climensional materials, to address the
difficulty of assembling
nanocomponents, and to improve the
thermal stability of nanostructures.
BIOMATERIALS
Biomaterials include, among
many things, the medical implants
carrier! by millions of Americans. Some
biomaterials are made from components
whose usefulness has been discovered
by serendipity. An example is
polymethy] methacrylate, or superglue,
which is used in intraocular lenses.
Another is shape-memory alloys, once a
curiosity but now used to keep aortal
stents round. The potential for newly
engineered materials to solve many of
the challenges for new implanted crevices is enormous
~ 1 1 · . ~
Particles,
diameter<] OOnm
Material with small
grain size, <1OOnm
Nanoscaie naultilayers
Material containing
nanoscale features
Carbon structures, e.g.,
C60, nanotubes, etc.
.
..
.
FIGURE 3-1 Examples of some basic nanomaterial
structures. SOURCE: Julia Weertman, Northwestern
University.
Drug Every systems have great commercial and societal impact. Traditional
internal drug delivery methods use polymeric materials that dissolve or diffuse the drugs.
One new approach is the use of microneedIes, currently mace from silicon, that can inject
drugs painlessly. Another approach is the "pharmacy on a chip," where conventional
lithography makes many reservoirs on a chip and electrical impulses selectively rupture a
membrane ant! deliver the required close of the chosen drug.
Materials for implementing the array technologies needled for genomic and
proteomic studies present new challenges. Making arrays of genes is relatively
straightforward, because all genes have very similar chemistries. However, forming
protein arrays is much more difficult, because proteins vary so widely. Moreover, simple
polymer substrates cannot provide the amount of information required. New materials
with new surface properties are needled.
14
OCR for page 15
MATERIALS IN FUTURE INDUSTRIES
Microfluidic devices can move fluids through a maze of microscopic channels
and chambers that have been fabricated with the same lithographic techniques used today
for microelectronics production. They can be used, for instance, to separate cells, and
they can have input channels as small as 10 micrometers. Although microfluidic devices
are cost competitive with conventional cell sorters, materials challens,P.~ still limit the
speed and capacity of the microfluidic approach.
~ ~ a.=, ~ v ... ...,.. ~ Ace_
The assembly of hybrid organic and inorganic materials exploits the ability of a
small amount of organic material to organize the inorganic component of a hybrid
material. An exciting example of an application for this type of structure is the use of
peptides to distinguish gallium arsenide from silicon and silicate.
1
MATERIALS FOR OPTICAL COMMUNICATIONS
Materials advances have enabled some of the great leaps in electronic switching
and communication over the past 30 years, as shown in Figure 3-2. In order to continue
this daunting trend, today's devices are moving steadily toward materials that use optical
characteristics to increase their functionality.
.
Optical materials that are already being implemented in communication systems
Include erbium-doped fibers that permit optical signals to be amplified without the use of
electronics. Implementation of this technology can lead to increases in capacity by a
factor of close to 1,000 when combined with wavelength-dispersive multiplexing, which
uses up to 80 or so multiple wavelengths, with each wavelength carrying a separate
communications channel. The resultant increase in power can mean that signal boosters
are needed only every 50 miles, allowing telephone calls and e-mails to be transmitted
optically across oceans or continents without going through an electronic system.
These and other innovative fiber materials are being used today. However, over
long distances, intrinsic fiber material nonlinearities fundamentally limit the system
performance. New materials and approaches to overcome these limitations and provide
linearity include photonic band gap materials and "holey" fibers. Fabrication of holey
fibers fibers designed with tiny holes along their length is difficult. but the nav~ff of
being able to engineer the fiber properties is considerable.
New systems are increasingly needed for routing the communications along these
high-capacity networks. These systems now resemble highways with complex
interchanges where signals are split and rerouted toward their final destination. One
enabling technology is MEMS, which can make such high-capacity switches with very
low losses and switching densities unmatched by electronic switches. The arrays of
mirrors can easily be scaled up, and switch times of milliseconds, while slow, are
sufficient.
Optical signal devices hold great promise for replacing electronic switching
devices. Optical-controlled switching will require a nonlinear gate materin1 ~ mntP.rinl~
. 1 1 , 1 , · ~
~ : _ _ A ~
_ ~ ~ ^~—* ~~— ~ A$~~ B ~~
~ecnnology Inal remains Immature. because optical-optical nonlinear interactions are
weak, such devices use proportionally more power. Advances in gate materials will be
needed to increase their efficiency.
15
OCR for page 16
MATERIALS AND SOCIETY
ODO
~ 1 0~3
I
CD
~~ ~0
_
~ ..
v
-~e
,.,...
it, ~ . ~ ~ - .... ~ .. ~ .... , ~
O.001 ~-'~'"' -' -~-:~ :~ ~~ 'I':: ~~.~'- ' ~.~.'.~ ~ ~ .' ' '.' ~: ~ -.~ ~ ~ ~'~ '.'.
~ 970 ~ 975 t 980 1985 ~ 990 ~ 995 2~)0Q 20~)5
FIGURE 3-2 Technology roadmap for lightwave electronics, showing the data rate capabilities enabled over the
past 30 years. The materials used for electronics have ranged from silicon to gallium arsenide to indium
phosphide. The devices these materials are used in are also many: They include bipolar transistors, metal oxide
semiconductor field-effect transistors (MOSFETs), metal electron semiconductor field-effect transistors
(MESFETs), heterojunction bipolar transistors (HBTs), and high-electron-mobility transistors (HEMTs). The
transmission characteristics these materials have enabled in optical carriers (OCs) have improved from less than
500 million bits per second (Mbps) to over 40 billion bits per second (Gbps). SOURCE: Cherry Murray, Lucent
Technologies.
COMPUTATIONAL MATERIALS SCIENCE
Computational approaches have ma(le tremendous progress at all length scales
relevant to materials. These inclucle the macroscale (human dimensions), the microscale
(atomic climensions), and the mesoscale, which bridges the two regimes.
At the macroscale, researchers have long used such traditional methods as finite
element analysis to predict mechanical and other properties of materials. These methods
are now being coupled with image processing approaches to impart aclclitional physical
cletail to the mociels.
At the smallest scales, quantum mechanical ah initio (or electronic structure)
calculations have predicted optical spectra in nanoscopic quantum clots. These models
also predict the great mechanical strength of carbon nanotubes. Despite the excitement
surrounding new materials, the simulation capabilities of these relatively new methods
are currently limited to small calculations, typically for less than a thousand atoms.
Improver! algorithms and computer speeds will be needled to mode! larger systems.
Bridging the considerable gap between quantum mechanical simulations of small
collections of atoms ant! macroscale calculations of materials properties are the molecular
and mesoscale simulation methods. These may include tens of thousands to a billion
atoms simulatecl using particle-basecl or field-based methocls. Such methods can provide
insight into materials phenomena on the scale of several nanometers to several hundreds
16
OCR for page 17
MATERIALS IN FUTURE INDUSTRIES
of microns, and on time scales from picoseconds to seconds or even hours, depending on
the material or process modeled. Dendritic growth during solidification and polymer
phase separation, for example, is often modeled with these methods.
A goal for computational materials science is to play the same role in materials as
molecular modeling does in the pharmaceutical industry. Challenges to reaching this goal
include developing approaches to seamlessly integrate multiscale simulation methods and
techniques to handle large quantities of data, training researchers, and sustaining the
multidisciplinary infrastructure needed to attack and solve the problems.
In general, the development of reliable mesoscale theory and methods will aid the
better understanding and development of complex materials such as self-assembled
nanotubes and quantum dots, bioinspired and biological materials, and nanoengineered
materials designed molecule by molecule.
Over the next decade, the use of computational methods to design, discover, and
optimize nanomaterials, biomaterials, and optical materials will become increasingly
prevalent. One workshop participant cited the view that the United States economy was
built on materials: steel, aluminum, glass, cast iron, and plastics. Although these
industries are still responsible for much of our growth, the new materials that are the
subject of this report will play an increasingly important role.
Comments from the Speakers
"Computational approaches to simulate materials and anticipate behavior enable a
modern approach to materials design, discovery, and optimization."
Sharon Glotzer, University of Michigan
"The enormous advances in optical communication systems over the past 5 years are
largely due to materials advances on many fronts."
Rod Alferness, Lucent Technologies
"Nanomaterials are an exciting but very disparate class of materials which come in an
ever increasing array of forms with a wide variety of applications."
Julia Weertman, Northwestern University
"Biomaterials encompass the traditional bioengineering of medical implants to newer
areas of drug delivery, tissue engineering, materials for array technologies, microfluidics,
and hybrid materials."
David Tirrell, California Institute of Technology
17
OCR for page 18
Representative terms from entire chapter:
computational materials
