InSites is a quarterly newsletter that highlights the personalities and projects of the Waste Management Research and Education Institute (WMREI) of The University of Tennessee. WMREI is an affiliate of the EERC.
WMREI was created in 1985 as a state-funded Center of Excellence. Research areas include solid-, hazardous-, and nuclear-waste management; waste minimization; and pollution prevention.
Biotechnology is the focal point of the institute's technical research, while issues involving public attitudes and federal/state policies related to waste-management issues are the primary concerns of the institute's policy research.
For additional information about InSites, or to be added to our mailing list, please write InSites, WMREI, The University of Tennessee, 311 Conference Building, Knoxville, TN 37996-4134, call 865-974-1156, or fax 865-974-1838. Or, if you prefer, email us.
Table of Contents
INSITES SCALES DOWN to the NANOMETER ,
By David Brill, Editor
PROCEED with CAUTION ,
By Jack Barkenbus
Nature Lights the Way ,
By Kris Christen
BALANCING PROMISE with PRUDENCE
,
Gary Sayler Keeping Microbes off the Menu Needling a Killer Tiny Switches, Huge Results Visualizing at the Nanoscale Joint Appointment Nanotech’s
Sensitive Side 
INSITES SCALES DOWN
to the NANOMETER
BIG SCIENCE HAS USHERED IN THE NEW millennium by thinking small. Very small.
The metric standard for this new science is the nanometer, which roughly measures
one-billionth of a meter (that’s eight zeros, if you care to count them).
To put that into perspective, consider that a human hair measures about 100,000
nanometers wide, and a dust mite measures 200,000 nanometers from tip to tail.
Minute though this scale may be, nanoscience is advancing technologies that
may soon revolutionize fields as wide ranging as medicine and agriculture,
data processing and textiles, transportation and environmental protection,
national security and food safety.
Researchers at the University of Tennessee (UT) are playing an important role
at the forefront of what many regard as the next industrial revolution. Much
of their research is taking place in collaboration with scientists from Oak
Ridge National Laboratory’s (ORNL) Center for Nanophase Materials Sciences,
one of five Centers created nationwide by the U.S. Department of Energy. Many
of UT’s nanoscientists hold joint appointments at both institutions. We open
this special 12-page issue with two thoughtful essays on the future of nanotechnology,
its potential, and the oversight and regulatory schemes that should play a
role in guiding its path. The first, “Proceed with Caution,” is by Jack Barkenbus,
policy director for UT’s Waste Management Research and Education Institute
(WMREI), the publisher of InSites. The second, “Nanotech’s Future: Balancing
Promise with Prudence,” is by WMREI’s director Gary Sayler.
The balance of this edition takes a look at some of the individual research
initiatives underway at UT and ORNL. We hope these stories incline you to
think expansively about an exciting—and rapidly evolving—science that operates
on the smallest of scales.
—David Brill, Editor
* * *
Contact David Brill, Director, The University of Tennessee.
PROCEED WITH CAUTION
Social oversight of nanotechnology needs to keep pace with the technology’s
growth and application.
Nanoscience and nanotechnology clearly have the potential to solve some of
our most daunting medical problems, help clean up the environment, and create
next-generation computers with huge advances in speed and information- storage
capacity. The enormous level of funding committed to supporting the multi-agency
National Nanotechnology Initiative, and the bipartisan backing the initiative
enjoys, are testimony to the strong, collective vision we have of science
and technology adding immeasurably to our future welfare. The United States
is not alone in this enterprise, as other countries in Europe and Asia are
also major investors in this arena.
The astonishing potential of nanotechnology and the excitement it engenders
among the scientific community and business leaders sometimes outpace public
understanding. Indeed, nanotechnology is difficult to portray in terms familiar
to the public and to those seeking to scrutinize its development. For one
thing, the notion of working at such a miniaturized scale is mindboggling.
For another, nanoscience is not a single discipline, but exists at the convergence
of biosciences, physics, chemistry, and materials sciences. In fact, nanoscience
and nanotechnology are less a distinct field than a further development and
refinement of existing sciences.
And finally, it is difficult for the industry growing up around the technology
to clearly describe the specific outcomes of its research and testing. Every
sector of society could possibly be affected by its development, but it is
impossible to predict whether, how, and when these sectors will be affected.
For these reasons, advocates generally tout the promise of nanotechnology
in grandiose but all-too-general terms. This is clearly a winning strategy
for garnering significant research funding but will not ensure smooth sailing
as nanotechnology’s promise and potential advance to actual commercialization.
Those seeking to advance commercialization of nanotechnologies will have to
be forthright, frank, and completely honest with the public regarding potential
risks. Any attempt to hide such concerns will ultimately fail and jeopardize
the entire enterprise. Some non-governmental groups have already provided
warning signals. The risks they posit range from the fairly familiar to the
apocalyptic. These risks include but are not limited to: l Ultrafine nanoparticle
inhalation, ingestion, or skin penetration: There is now abundant evidence
that small-particle inhalation or ingestion can have serious health consequences.
A significant number of toxicological animal studies are only now getting
underway to provide experimental answers to health concerns.
The health risks associated with the production, use, and disposal of nanoparticles
is the first major issue requiring attention.
Privacy issues: Nanotechnology may have a huge impact on the creation, storage,
and utilization of information. Clearly, there are large potential benefits
when information can be gathered and stored in a cheap, ubiquitous manner—
but all sorts of privacy issues must be addressed as well. The ability to
monitor, record, and store copious amounts of data presents opportunities
for human surveillance that go well beyond what is possible today.
Ownership concerns: Concentration of nanotechnology ownership could be a serious
concern. Patent offices already are being overwhelmed with nanotechnology
applications (over 300,000 total applications in the United States alone),
with companies seeking proprietary control over processes they view as the
key to future profits. Clearly we must strike a balance between the public
interest in discovery and the private interest in reaping the financial benefits
from that discovery. This appears to be a particular concern in the area of
drug delivery, where proprietary interests may thwart dissemination of important
discoveries and prevent robust competition.
l Molecular manufacturing/machines: This involves the most futuristic scenarios
involving the merger of robotics, genetic engineering, and nanotechnology
to produce nanobots that can circulate in the human bloodstream and attack
diseases inside the human body. Suffice it to say, this is the most revolutionary
and transformative vision for nanotechnology. It is also the most controversial.
Critics fear that this noble goal will inevitably lead to molecular machines
that selfreplicate and spin out of human control —leading to the end of life
on Earth as we know it.
The argument centers on, first, whether these nanobots can even be created,
and, second, whether humans would have to cede control if, in fact, they are
created. The controversy was heightened in an April 2000 article by Bill Joy
in Wired magazine bearing the provocative title, “Why the Future Doesn’t Need
Us.” Joy, a co-founder of Sun Microsystems, gave credence to the fear of those
who worry that only “gray goo” will survive the nanotechnology revolution.
The argument shows no sign of abating.
Unfortunately, we have few institutions today that provide science and technology
oversight in a balanced and measured fashion. The U.S. Congress Office of
Technology Assessment used to provide this service before it was prematurely
terminated in 1995. In its absence we will have to rely on episodic studies,
one of which was recently commissioned by the 21st Century Nanotechnology
Research and Development Act, passed by Congress in late 2003.
In the absence of definitive assurances of safety, one nongovernmental organization,
the Action Group on Erosion, Technology and Concentration (ETC), has called
for a precautionary approach involving a moratorium on further commercial
development until concerns can be resolved. While precaution is justified,
it does not follow that a moratorium is the proper tool for exercising precaution.
There will never be a time when risks are completely resolved and industry
given an unqualified green light to proceed. Even more to the point, governments
are not going to impose such a blunt instrument on industry when the potential
benefits from commercialization are so enormous. Calling for a moratorium,
therefore, is a nonstarter.
One possible institutional approach to continuing review and oversight of
nanotechnology is through the creation of a global public policy network devoted
exclusively to nanotechnology. Networks are multi-sectoral (government, corporate,
and non-governmental) alliances drawing international participation around
specific societal issues. Those networks already existing and cited frequently
include the World Commission on Dams, the Global Water Partnership, Roll Back
Malaria, and the Consultative Group on International Agricultural Research
(CGIAR). A nanotechnology network could serve as a unique and valued international
forum for promoting public and political awareness of nanotechnology on a
continuous basis.
In short, nanoscience has significant potential to change society for the
better, but attention to its dark side is essential if we hope to avoid dashed
hopes and aspirations and the potential complications of this evolving technology.
* * *
Jack Barkenbus serves as executive director for the University of Tennessee’s (UT) Energy, Environment and Resources Center and policy director for UT’s Waste Management Research and Education Institute.
TAKING ADVANTAGE OF PHOTOSYNTHESIS, a process nature has
perfected, researchers are hoping to harness the sun’s rays in a way that
could prove much more effi- cient than traditional photovoltaic (PV) systems.
PVs convert light energy into electrical energy.
In photosynthesis, chloroplasts inside green plant cells convert sunlight
into chemical energy, storing it as a form of sugar while simultaneously releasing
oxygen. This job is done by a certain protein complex, known as a reaction
center, which uses the light energy to generate a high-energy electron and
move it across the chloroplast cell membrane through a phenomenon known as
a photosynthetic charge separation.
This photochemical reaction is what drives all living things, and it works
with near 100-percent efficiency, says Barry D. Bruce, a membrane biochemist
with the University of Tennessee’s (UT) Department of Biochemistry and Cellular
and Molecular Biology. Together with researchers from the Massachusetts Institute
of Technology, Bruce has taken this isolated reaction center and inserted
it into a nanoscale PV device that allows the electrons to jump across to
a semi-conducting layer used to carry the current, creating a sort of miniaturized
battery.
The idea is that the molecular circuitry within these photosynthetic protein
complexes could eventually be used in energy production in the same way that
traditional, silicon-based PV solar cells are used for power, Bruce says.
Moreover, this technology could help clear some of the hurdles that traditional
PV arrays have come up against—namely high production costs, limited availability
of the rare metals used to produce the solar cells, and low power-conversion
efficiencies that peak below 25 percent.
“We still don’t really understand why this process works as well as it does,
and nothing we’ve ever been able to make works anywhere near this efficiently,”
Bruce notes. In theory, he predicts that this nature-inspired device could
work with 40–60 percent efficiencies if “we could approximate in the solid
state what nature has done in the biological state.”
As things now stand, the researchers have a conversion efficiency measuring
less than 15 percent, so they’re looking at ways to increase the electrical
contact with the semi-conducting layers to ensure that every electron generated
becomes part of the current.
Even more important, they need to find a way to extend the stability of the
protein complexes. “We’re taking these things completely out of their natural
cell setting and embedding them between organic semi-conductor layers, so
they’re no longer in an aqueous environment,” Bruce explains.
He and his colleagues are trying to determine just how long the protein complexes
can survive in this form, determine what factors might be causing them to
deteriorate, and address those problems so that they can extend the system’s
lifespan.
Ultimately, what the researchers hope to develop is a device more efficient
than traditional PV solar cells but less costly and energy intensive to manufacture.
And if they’re successful, “we could have a renewable and clean energy system,”
Bruce says.
* * *
Contact Barry D. Bruce, Department of Biochemistry and Cellular and Molecular Biology, The University of Tennessee, F423 Walters Life Science Bldg., Knoxville, TN 37996, call 865-974-4082, or e-mail bbruce@utk.edu.
BALANCING PROMISE with
PRUDENCE
The government-sponsored National Nanotechnology Initiative
represents an annual taxpayer research and development (R&D) investment of
about $1 billion, and many scientists, researchers, and policymakers regard
this as a reasonable —even vital—investment. Indeed, this critical new technology
represents an arena in which the United States can little afford to lose its
technological edge in its competition with Japan and Western Europe, which
are both vying for supremacy in what is expected to be the next industrial
revolution.
In the past five years, foreign and domestic nanotechnology investments (both
public and private) have begun to spin off several commercial products. In
some cases these spin offs are of surprisingly large magnitude, such as the
production of fullerenes and carbon nanotubes —two of the structural building
blocks of nanotechnology. Once painstakingly produced in small quantities
and at considerable time and expense, these devices can now be produced in
bulk.
Fullerenes are clusters of carbon atoms that form closed, hollow cages of
exceptional strength. Industry is using these minute structures, which are
shaped like soccer balls, to make paints, polymers, drugs, and antioxidants.
Meanwhile, manufacturers are also turning to the carbon nanotube—a hexagonal
network of carbon atoms that has been rolled up to make a seamless cylinder
and capped on both ends with half a fullerene—to create new products or improve
existing ones.
These tubes, at about 1/500th the width of a human hair, boast 100 times the
tensile strength of steel at one-sixth the weight and might be used to create
auto tires that never go flat, tennis balls that never lose their bounce,
or textiles that can monitor soldiers’ biological systems and help protect
them from biological and chemical weapons. These tubes are also capable of
carrying electricity with virtually no resistance and might be used as miniature
semiconductors. The applications for these devices are virtually limitless.
GROWTH INDUSTRY
The National Science Foundation (NSF) projects that nanotechnology will grow
to a $1-trillion industry by 2015. Those states and countries embracing and
encouraging both nano R&D and commercialization are taking a qualified risk
that related job growth and wealth creation will rival that experienced during
the boom in information technologies and telecommunications over the past
several decades.
Why, then, despite all this promise, does at least one nongovernmental organization,
the Action Group on Erosion, Technology and Concentration (ETC), call for
a moratorium on nanotechnology research, development, and demonstration (RD&D)
until the environmental and cultural implications of the technology are fully
evaluated? (In the 1990s, ETC, then known as the Rural Advancement Foundation
International, took a similar cautionary stand in the debate over biotech/genetically
modified [GM] food.) Is it because there are clearly identi- fied technology
risks so severe that governments must intervene to protect the world’s population?
Perhaps it is the need to find a new cause to take up, now that Europe is
competitive in biotechnology and is beginning to embrace GM foods. More likely
it is due to “overhype” of nanotechnology in some quarters, with a concomitant
dearth of knowledge among the lay public about its true potential and physical
characteristics.
To fully evaluate the socio-environmental impacts of nanotechnology, three
issues must be addressed (1) the breadth of the technology, (2) positive implications
for society and the environment, and (3) identification of hazards.
BREADTH OF SCOPE
For the most part, public concern over nanotechnology’s environmental risks
is associated with two facets of this new science: the eventual ability of
nano-elements (nanobots) to self-replicate, and the indestructibility of carbon
nanotubes. In fact, these realities represent a fertile but relatively tiny
slice of the entire field of nanoscience and technology.
The broader RD&D horizon includes the synthesis of entirely new material composites,
polymers and nano crystals, new electronic circuitry and assembly, new drugs
and delivery systems, new information processing and computing, new sensors
and diagnostic devices, and new biomimetic systems—devices with nanoproperties
that mimic biological functions and structures.
While some of this technology is already invading the marketplaces in the
form of new protective coatings for fabrics (soil- and water-resistant trousers,
for example), other aspects of the technology seem foreign and exotic. However,
one must remember that nanoscale research is not new; chemists, molecular
biologists, geneticists, and biochemists have been working with nanoscale
structures and devices for decades.
Consider, for instance, that most of the elements within individual cells
and viruses are nanoscale (even subnanoscale) and are models, if not templates,
for new nanostructures and technology. Consequently, the science and technology
community is quite comfortable working with and exploiting nanoscience and
nanostructures. The point of this argument is multifold.
First, there are numerous nanoscale materials and processes beyond carbon
nanotubes, and scientists have been working with some of them for years.
Second, nanoscale properties and processes, while novel, are not necessarily
unique. Consider, for instance, that the earliest human cave-dwellers were
synthesizing fullerenes via candle soot.
Likewise, autonomous assembly of chips, computers, and the like has been discussed
for decades. Yet, the "gray goo" concept of self-replicating nanobots overtaking
the Earth is not even on the horizon, notwithstanding the recent theoretical
modeling by General Dynamics Advanced Information Systems.
A SOFTER REGULATORY HAND
Regardless of its path, nanotechnology will be regulated at the governmental
level. The U.S. Food and Drug Administration clearly seeks an active role,
for instance, and will share regulatory responsibility with the U.S. Environmental
Protection Agency (EPA). EPA’s statutory authority will fall under the Toxic
Substances Control Act (TSCA). Enacted by Congress in 1976, TSCA authorizes
EPA to track industrial chemicals produced or imported into the United States.
More recently, TSCA’s regulatory reach was expanded to include biotechnology.
Likewise, TSCA will ultimately be applied to nanotechnology as well.
These facts are not new, and University of Tennessee law professor Glen Reynolds
pointed out the regulatory necessities several years ago in his now widely
cited article “Forward to the Future: Nanotechnology and Regulatory Policy”
Meanwhile, we should not focus too intently on the potential liabilities of
nanotechnology while failing to recognize the huge positive applications and
their implications for the environment. Among these are new processes to drastically
reduce raw material needs, lower energy demands, and reduce releases of toxic
intermediates and byproducts.
Currently, active areas of research, including field applications, are underway
to demonstrate new waste-treatment technology and remediation processes. Many
of the technologies are attempting to take advantage of nanomaterials. One
such technology involves passing pollutants through nano-coated titanium dioxide
(TiO2) honeycomb filters. These devices convert pollutants into harmless end
products.
Future applications will likely include carbon nanotubes capable of storing,
and even generating, hydrogen gas, which many researchers believe will provide
a renewable and environmentally benign energy source for the future. Other
applications, such as nanolubricants, will lessen demand for lubricants derived
from fossil fuels and toxic cutting oils used in machining.
HAZARD IDENTIFICATION
The question is not if nanotechnology will be regulated, but how it will be
regulated in response to identified hazards and risks. The Foresight and Governance
Project of the Woodrow Wilson International Center for Scholars has done an
effective job of defining some of these hazards from a TSCA perspective in
“Nanotechnology and Regulation: A Case Study Using the Toxic Substance Control
Act”
This analysis certainly does not advocate a tight moratorium on the technology,
as suggested by the ETC group in “The Big Down Atomtech: Technologies Converging
at the Nano-scale”
Hindsight reveals that the overly cautious assessments associated with environmental
biotechnology severely retarded growth and application of that technology.
The current fear is that, if similar approaches are applied to nanotechnology,
this new science could suffer a similar fate.
There are specific concerns that carbon nanotubes and other nanoparticles
represent toxic hazards. Furthermore, some of these substances may be biomagnified,
that is, they may become concentrated in increasing levels in the tissues
of living organisms. These are legitimate concerns and highly deserving of
investigation. Further, if problems are detected, we should institute appropriate
controls quickly. However, unlike genetically engineered organisms, nanomaterials
do not autonomously replicate—at least not at the current level of technology—and
thus represent relatively controllable “new chemicals.”
Other problems have been noted relative to analyzing for nanomaterial in the
environment and in biota. Currently, adequate and sensitive analytical methods
do not exist for these materials and thus must be developed. It is hard to
identify a hazard if you don’t have the tools necessary to detect and study
it. Such limitations make the process of risk assessment even more ambiguous.
At the same time, the environmental fate (biodegradation, hydrolysis, photo
oxidation, etc.) of many nanomaterials must also to be addressed. While vast
resources have been invested in synthesis of nanomaterials, very few have
been devoted to studying what happens to these materials once they’ve entered
the environment.
THE VISION
There is no pulling back from nanoscience and technology. The investments,
bene- fits, and commercial gains are just too large. As with any new technology,
risks of social and environmental damage do exist, but they do not appear
to be industry wide and, at the present time, are unquantified and unquantifiable.
Regulation of the technology is surely coming, but neither the scientific
community nor the public will be well served by a heavy-handed regulatory
structure. A prudent approach would combine a more relaxed regulatory scheme
with significantly increased funding for social and environmental research
concerning the technology. Currently, only a tiny fraction of the national
nanotech investments are targeted at these issues.
* * *
Contact Gary Sayler, ETCFC, The University of Tennessee, 311 Conference Center Building, Knoxville, TN 37996-4134. Visit the ETCFC at http://eerc.ra.utk.edu/etcfc/index.html.
* * *
Contact Jochen Weiss, Department of Food Science and Technology, The University of Tennessee, 2605 River Road, Knoxville, TN 37996, call 865-974-2753, or e-mail jweiss1@utk.edu.
* * *
Contact Jochen Weiss, Department of Food Science and Technology, The University of Tennessee, 2605 River Road, Knoxville, TN 37996, call 865-974-2753, or e-mail jweiss1@utk.edu.
IN THE PAST DECADE, WE’VE SEEN personal computers go from
occupying most of our desktops to laptops that weigh six pounds or less. Even
as their size has decreased, these computers have become much more powerful.
Thanks to nanotechnology, as electrical switches shrink more and more, computers
and the machines they drive will become even smaller and more powerful.
“With nanomaterials, the records stored in a computer allow the connections
that facilitate the user’s demands to be 100 times smaller than they are now,”
says George Pharr, professor in the University of Tennessee’s (UT) Materials
Science and Engineering Department. “The higher the density of the information,
the smaller the item can be made,” he says.
How? It has to do with switches. Some materials—aluminum, for instance—are
excellent conductors of electricity. The non-conductivity of other materials—
ceramic, for example—means they can be used to stop the flow of electricity.
The differences between materials’ conductivity can be exploited to make different
types of switches: A conducting material such as aluminum is used to form
conduits to facilitate the flow of electricity; switches made of a non-conducting
material such as ceramic are used to interrupt the flow and turn off the circuit.
The smaller the circuits, the smaller the switches, and ultimately, the smaller
the device that contains them. Circuit boards are collections of circuits
and switches, and the smaller those boards, the more of them that can be crammed
into a device.
The switches can be made smaller because the alternating layers of conducting
and nonconducting materials are constructed in nanowidths.
Where will these nanoswitches lead technology? Ward Plummer, a UT distinguished
professor of physics, predicts a computer that will fit easily into a shirt
pocket. Plummer is director of UT’s Tennessee Advanced Materials Laboratory
(TAML) and task leader for the Complex Nanophase Materials System at the Center
for Nanophase Materials Sciences at Oak Ridge National Laboratory. “With these
new computers, there would be no boot-up,” he says. “You would just turn it
on, and it would be ready for use.”
And instead of a conventional computer screen, you might don glasses or goggles
that provide the visual display. Though miniature, the pocket-sized computer
would be more powerful than today’s highest-end laptops.
Tomorrow’s cellphones, says Pharr, could be as small as an earplug. Cellphones
use tiny computers made up of even tinier chips and circuits to store telephone
numbers, to relay signals to towers, and, in the case of picture-phones, to
relay photographs between callers.
Nanoswitches are also being made utilizing photons, which can create even
more speed. Light is transmitted faster than heat, for example, so photo-sensitive
materials react quicker than those triggered thermally.
As an added benefit, smaller sizes mean greater energy efficiency: Nanosized
switches use nanosized amounts of electricity.
Nanoscale also provides scientists with the ability to manufacture devices
quicker and less expensively, notes David Joy, distinguished scientist in
UT’s Department of Biochemistry and Cellular and Molecular Biology. The minute
sizes conserve space and electricity, and the tiny, more powerful switches
will increase manufacturing speeds.
* * *
Contact George Pharr, Department of Materials Science and Engineering, The University of Tennessee, 434 Daugherty Engineering Building, Knoxville, TN 37996, call 865-974-8202,or e-mail pharr@utk.edu. Contact Ward Plummer, Department of Physics, The University of Tennessee, 303 South College, Knoxville, TN 37996, call 865-974-3055, or email eplummer@utk.edu.
IN NOVEMBER 2003, THE UNIVERSITY OF Tennessee’s (UT) Center
for Nanomaterials Science, Imaging and Nanomanipulation took delivery of a
JEOL 6000, a Japanese designed direct-write electron beam lithography tool.
David Joy, task leader for the Center, calls the JEOL the 21st-century equivalent
of the 19th century’s lathe in its impact because of its ability to engineer
materials.
There are only about a dozen JEOL 6000s in the United States, which means
UT has joined other institutions at the forefront of nanotechnology research.
“Now we can control what we are doing,” says Joy, who also serves as distinguished
scientist in UT’s Department of Biochemistry and Cellular and Molecular Biology.
Before the purchase of the JEOL, UT scientists involved in nanotechnology
research had been working in the dark, so to speak, then taking their experiments
to Cornell University in Ithaca, New York, to check their results using that
school’s beam writer. “Now we can develop our own nanotools and processes
and get our own patents,” Joy says.
In one mode of operation, the beam writer sends electron beams through different
gases concentrated just above the surface of the target material. Different
gases produce different results. The object might be to etch—or to eat away—parts
of a metal. Or it might be metal deposition—laying down a metal onto another
material.
The processes may differ, but they all allow UT scientists to “fabricate structures
for measuring characterization and for calibrating at the nanoscale,” says
Joy. One application already in use involves the process by which microcircuits
—the building blocks of computers —are manufactured. A glass mask with billions
of metal lines deposited on it is used to create the microcircuits. A set
of masks for a computer CPU now costs around $2 million. During routine use,
the masks can get scratched or their metal lines can be broken.
Using the beam writer, scientists have created a tool that can repair the
masks by taking out the scratches or re-connecting the broken lines, Joy says.
That extends the useful life of the mask and helps bring down the costs of
manufacturing microcircuits and the devices that are based on them.
* * *
Contact George Pharr, Department of Materials Science and Engineering, The University of Tennessee, 434 Daugherty Engineering Building, Knoxville, TN 37996, call 865-974-8202,or e-mail pharr@utk.edu. Contact Ward Plummer, Department of Physics, The University of Tennessee, 303 South College, Knoxville, TN 37996, call 865-974-3055, or email eplummer@utk.edu.
TODAY, DOCTORS DETERMINE HOW WELL a patient’s artificial
knee or hip implant is working through a standard X-ray and clinical examinations.
Tomorrow, they may be able to get more and better information through tiny
nano-sensors embedded in artificial joint replacements that can detect infections
and implant failure. “These implantable sensors will revolutionize the medical
industry,” predicts Richard Komistek, a professor with the University of Tennessee’s
(UT) Department of Mechanical, Aerospace, and Biomedical Engineering and director
of the joint UT-Oak Ridge National Laboratory Biomedical Center.
Currently, when doctors detect an infection growing, they have to remove the
joint implants, leaving the patient immobilized until the infection can be
stemmed and a new joint put in.
“It’s a very tough procedure on the patient, and costs the healthcare system
upwards of $75,000-$125,000 every time an infection occurs,” Komistek explains.
But with nano-sensors embedded in the joints, “it’s almost like someone is
living inside a person’s knee joint,” offering doctors an in vivo diagnostic
tool, Komistek notes. Using a hand-held, device similar in size to a Palm
Pilot®, a doctor could dial in the serial number of the sensor for a particular
patient and receive a read-out of any problems the patient may be encountering.
And because the sensor is inside the joint itself, the doctor could get information
on how the implant materials are wearing. Most important, the sensor could
read chemical changes occurring inside the joint, and at the earliest onset
of an infection, it would send out a signal, Komistek says.
Five companies have expressed interest in licensing the technology once it’s
developed.
Other potential applications include diagnostic use as early warning signs
for the onset of diabetes, cancer, and other life-altering illnesses. Diabetics,
for example, might receive a sensor that, throughout their lifetime, would
detect when their blood-sugar levels are getting out of control. “You want
to be able to catch these problems as early as possible,” Komistek explains.
* * *
Contact Richard Komistek, Department of Mechanical, Aerospace, and Biomedical Engineering, The University of Tennessee, 313 Perkins Hall, Knoxville, TN 37996-2030, call 865-974-4159, or e-mail rkomiste@utk.edu.
Cantilevers (think nanoscale diving boards) are simple
machines that can change shape when they interact with other materials. Panagiotis
Datskos, research associate professor in the University of Tennessee physics
department, designs and builds tiny systems centered on cantilevers, key elements
in sensors that are used in everything from automobile airbags to home security
systems.
The cantilevers are part of a growing collection of nano devices known as
nano-electro mechanical systems (NEMS). Despite their tiny size, NEMS can
be made sensitive enough to pick up the body heat of a sedentary person in
a room. Today’s motion detector, mounted on the wall with its thermal-detection
“eye” aimed at the door as part of a security system, could simply be a part
of the room’s paint with the use of NEMS.
Different materials, whether an element such as silicon or an alloy such as
brass, react differently when exposed to chemicals, magnetic forces, thermal
factors, light, and the force of gravity. A cantilever that is a combination
of two different materials with differing properties is going to change shape
or resonance frequency if one element reacts while the other does nothing.
For example, if silicon is coated with gold and exposed to heat, the silicon
shrinks but the gold does not, and that bends the cantilever. When the cantilever
bends, it could trigger an alarm or turn on a light. The same principle, on
a larger scale, is what makes the thermostat in our heating and cooling systems
turn on our furnaces or air conditioners.
The amount of change tells Datskos and his team how much energy is used in
that transaction so they can determine which materials work quickest and most
efficiently. Then the materials that are best suited for a particular application
would be used to manufacture sensors for that application.
“We can use any semiconductor, any metal, or any insulator for the studies,”
says Datskos.
Nanosensors are already in use in a variety of ways. A tiny sensor, triggered
by a change in gravity force caused by sudden deceleration, can instantly
detect the impact of a crash, deploying a protective airbag in a vehicle.
Nanosized sensors can be deployed in greater quantity and in smaller spaces
in a vehicle than can larger-sized versions. Tiny sensors embedded in building
material can monitor air quality in a home, in an industrial factory, or immediately
outside the plant. If the level of carbon monoxide suddenly increases, for
example, a sensor designed to be sensitive to carbon monoxide would trigger
an alarm.
Or a sensor can be included in a stent used to repair a damaged artery, allowing
constant in vivo monitoring to make sure the stent functions as it should.
If the oxygen level in the blood changes, the sensor would detect it and trigger
a reaction in a small monitor carried by the patient or the physician.
An array of sensors, each sensitive to a particular chemical, could be used
to detect the presence of any of those chemicals, “replacing the dog’s nose,”
as Datskos puts it. One sensor could be sensitive to mustard gas, another
to anthrax, for example. A soldier’s uniform might contain a small cloth patch
containing a grouping of such sensors. Or a drone carrying an array of sensors
might be flown ahead of a group of soldiers. Toxic chemicals would be detected
and that information transmitted immediately back to the troops.
The use of gold on cantilevers demonstrates another aspect of nanoscience:
Materials, including elements, may have different properties at nanosize than
they do normally. Gold, useful in creating cantilevers because of its malleability,
has always been considered an inert element. But at nanosize, when prepared
appropriately, gold becomes a facilitator for capturing other chemicals. Because
in larger sizes it remains inert—only slightly susceptible to oxidation, for
example—it is easier to ship and store than other materials. Then, when it
is time for nanosizing, the gold is ready for use, says Datskos.
* * *
Contact Panagiotis Datskos, Department of Physics and Astronomy, The University of Tennessee, 401 Nielsen Physics Building, Knoxville, TN 37996, call 865-974-3342, or e-mail datskos@utk.edu
