UNIVERSITY INSTITUTE OF ENGINEERING AND TECHNOLOGY, KURUKSHETRA UNIVERSITY, KURUKSHETRA
A REPORT ON NANOTECHNOLOGY
YEAR : 2012
SUBMITTED TO: DR. C.C. Tripathi HOD, ECE Deptt. UIET, KUK
SUBMITTED BY: Puneet Dubey 2508023 ECE-A (8th sem) 1
TABLE OF FIGURES FIGURE NAME
PAGE NO.
Nanofly
5
Nanoscale
7
Nanodevice
12
Gold particles carrying anticancer drugs
13
Electron micrograph of typical silicon nanocomposite
15
Quantum dots
16
Nanocrystals
16
Replicator
22
Assembler
23
Components of MEMS
25
Micromachined electro-statically-actuated micromotor
26
Micromachined resonator fabricated by the MNX
27
Types of Hazards to Humans
28
Hazards to Environment
31
Hazards to aquatic life
31
2
TABLE OF CONTENTS
NAME
PAGE NO.
Abstract
4
Introduction to Nanotechnology
5
How small is Nanoscale
6
Present work in Nanotechnology
12
Nanotechnology Products
15
Future of Nanotechnology
21
Future Products
23
What is MEMS
24
Hazards of Nanotechnology
28
Conclusion
32
Bibliography
33
ABSTRACT 3
Nanotechnology is the study of manipulating matter on an atomic and molecular scale. Generally, nanotechnology deals with developing materials, devices, or other structures possessing at least one dimension sized from 1 to 100 nanometres. Quantum mechanical effects are important at this quantum-realm scale. Nanotechnology is very diverse, ranging from extensions of conventional device physics to completely new approaches based upon molecular self-assembly, from developing new materials with dimensions on the Nano scale to direct control of matter on the atomic scale. Nanotechnology entails the application of fields of science as diverse as surface science, organic chemistry, molecular biology, semiconductor physics, micro fabrication, etc. There is much debate on the future implications of nanotechnology. Nanotechnology may be able to create many new materials and devices with a vast range of applications, such as in medicine, electronics, biomaterials and
energy
production.
On
the
other
hand,
nanotechnology raises many of the same issues as any new technology, including concerns about the toxicity and environmental impact of nanomaterials,[1] and their potential effects on global economics, as well as speculation about various doomsday scenarios. These concerns have led to a debate among advocacy groups and governments on whether special regulation of nanotechnology is warranted.
4
INTRODUCTION TO NANOTECHNOLOGY:One of the biggest scientific trends of the 21st century has been centered
on something
incredibly small: nanotechnology. But what is nanotechnology? That is the most difficult question to answer, even though it’s all over the news these days. The crux of the problem is that it is beyond the understanding of most people. Unless we have studied it extensively in university we won’t know what a quantum dot is. We will need to know the underlying science that drives it, the tools we use to apply it, and the potential benefits and dangers of it. Nanotechnology is a broad term for the
application
of
scientific
understanding towards fabricating devices
and
materials
at
the
nanometer scale. Nanotechnology takes its name from a unit called nanometre-nm, which means it’s the one billionth of a meter. [1nm = nanometer (1,000,000,000 nm per m, or 10 -9m)].Nanotechnology is
Fig: nanofly
primarily characterized by its overall dimension: the Nano-world. The Nano-world exists at the level of single molecules and atoms-the size of a millionth of a millimetre. Nanotechnology involves building sophisticated products from the molecular scale. As the molecule is the smallest particle of matter that exists independently, it cannot be ruled by any of us, but the technologists have started ruling the same understanding the molecular world as a tough process. This kind of molecular manufacturing will in fact result in high quality, smart and intelligent products that are 100% efficient, produced at low cost with little environmental impact. Nanotechnology is expected to have an enormous potential for innovation because it may create effects which have not yet been feasible with any other technologies. The far reaching possibilities of nanotechnology development, which are currently being assessed according to feasibility, find their echo in partly extreme judgments of the technology. The specific characteristics of this dimension are that nano-particles show a completely different behaviour to their larger, coarser pendants. The relatively big specific surface of nano-particles usually leads to an increase in their chemical reactivity and catalytic activity. The relatively small amount of atoms within nano-particles offsets the quasi-continuous solid state of the particle, leading to new, deviating, optical, electrical and magnetic features. From these basic 5
features and characteristics of Nano-technology, a number of possible positive and problematic (negative) effects can be derived. Nanotechnology is very diverse, ranging from extensions of conventional device physics to completely new approaches based upon molecular self-assembly, from developing new materials with dimensions on the nanoscale to direct control of matter on the atomic scale. Nanotechnology entails the application of fields of science as diverse as surface science, organic chemistry, molecular biology, semiconductor physics, microfabrication, etc. "In not too many decades we should have a manufacturing technology able to: Build products with almost every atom in the right place; Do so inexpensively; Make most arrangements of atoms consistent with physical law. Often called nanotechnology, molecular nanotechnology or molecular manufacturing, it will let us make most products lighter, stronger, smarter, cheaper, cleaner and more precise." Nanotechnology: It's a Small, Small, Small, Small World By Ralph C. Merkle, Ph.D. Many materials, once they are individually reduced below 100 nanometres, begin displaying a set of unique characteristics based on quantum mechanical forces that are exhibited at the level. Due to these quantum mechanical effects, materials may become more conducting, be able to transfer heat better, or have modified mechanical properties. Nanotechnology is a recently emerging and rapidly growing field whose dynamics and prospects pose many great challenges not only to scientists and engineers but also to society at large. HOW SMALL IS NANOSCALE:To give an idea of the size of a nanometre (nm) here are some examples: • Typical red blood cell, 7000 nm in width, 2000 nm in height • Common cold virus, 25 nm • Width of DNA molecule, 2 nm • Silicon atom, 0.2 nm Nanotechnology inhabits the world of cells, viruses and even DNA. For example, by volume, a nanoparticle 2 nm in size would be over 10 billion times smaller than a red blood cell. To put this into context if the nano particle in question was the size of a person, then that blood cell would be approximately the size of the City of London. This means that when dealing with the risks, the effect on cells should be considered. 6
Let's start BIG, with something you can get your hands on (so to speak): A meter is about the distance from the tip of your nose to the end of your hand (1 meter = 3.28 feet). One thousandth of that is a millimeter. Now take one thousandth of that, and you have a micron: a thousandth of a thousandth of a meter. Put another way: a micron is a millionth of a meter, which is the scale that is relevant to - for instance - building computers, computer memory, and logic devices. Now, let's go smaller, to the nanometer: A nanometer is one thousandth of a micron, and a thousandth of a millionth of a meter (a billionth of a meter). Imagine: one billion nanometres in a meter.
Fig: Nanoscale
Another perspective: a nanometer is about the width of six bonded carbon atoms, and approximately 40,000 are needed to equal the width of an average human hair. Another way to visualize a nanometer: 1 inch = 25,400,000 nanometers 7
Red blood cells are ~7,000 nm in diameter, and ~2000 nm in height White blood cells are ~10,000 nm in diameter A virus is ~100 nm A hydrogen atom is .1 nm
Nanoparticles range from 1 to 100 nm Fullerenes (C60 / Buckyballs) are 1 nm Quantum Dots (of CdSe) are 8 nm Dendrimers are ~10 nm DNA (width) is 2 nm Proteins range from 5 to 50 nm Viruses range from 75 to 100 nm Bacteria range from 1,000 to 10,000 nm For our purposes, nanometers pertain to science, technology, manufacturing, chemistry, health sciences, materials science, space programs, and engineering. Nanotechnology is the understanding and control of matter at dimensions of roughly 1 to 100 nanometers, where unique phenomena enable novel applications. Encompassing nanoscale science, engineering and technology, nanotechnology involves imaging, measuring, modeling, and
manipulating
matter
at
this
length
scale.
At the nanoscale, the physical, chemical, and biological properties of materials differ in fundamental and valuable ways from the properties of individual atoms and molecules or bulk matter. Nanotechnology R&D is directed toward understanding and creating improved materials, devices, and systems that exploit these new properties.
Somethings that become Possible with Mature Nanotechnology : •
Nearly free consumer products 8
•
PC's billions of times faster than today
•
Safe and affordable space travel
•
Virtual end to illness, aging, death
•
No more pollution and automatic clean-up of existing pollution
•
End of famine and starvation
•
Superior education for every child on Earth
•
Reintroduction of many extinct plants and animals
•
Terraforming Earth and the Solar System
The following devices and capabilities appear to be both physically possible and practically realizable: •
Programmable positioning of reactive molecules with ~0.1 nm precision
•
Mechanosynthesis at >106operations/device · second
•
Mechanosynthetic assembly of 1 kg objects in <104 s
•
Nanomechanical systems operating at ~109 Hz
•
Logic gates that occupy ~10–26 m3 (~10– 8 m3)
•
Logic gates that switch in ~0.1 ns and dissipate <10– 21 J
•
Computers that perform 1016 instructions per second per watt
•
Cooling of cubic-centimeter, ~105 W systems at 300 K
•
Compact 1015 MIPS parallel computing systems
•
Mechanochemical power conversion at >109 W/m3
•
Electromechanical power conversion at >1015 W/m3
•
Macroscopic components with tensile strengths >5×1010 Pa
•
Production systems that can double capital stocks in <104 s
Of these capabilities, several are qualitatively novel and others improve on present engineering practice by one or more orders of magnitude. Each is an aspect or a consequence of molecular manufacturing.
Assumptions, principles, and some specific recommendations intended to provide a basis for responsible development of molecular nanotechnology 9
Development Principles 1. Artificial replicators must not be capable of replication in a natural, uncontrolled environment. 2. Evolution within the context of a self-replicating manufacturing system is discouraged. 3. Any replicated information should be error free. 4. MNT device designs should specifically limit proliferation and provide traceability of any replicating systems. 5. Developers should attempt to consider systematically the environmental consequences of the technology, and to limit these consequences to intended effects. This requires significant research on environmental models, risk management, as well as the theory, mechanisms, and experimental designs for built-in safeguard systems. 6. Industry self-regulation should be designed in whenever possible. Economic incentives could be provided through discounts on insurance policies for MNT development organizations that certify Guidelines compliance. Willingness to provide self-regulation should be one condition for access to advanced forms of the technology. 7. Distribution of molecular manufacturing development capability should be restricted,
whenever possible, to responsible actors that have agreed to use the Guidelines. No such restriction need apply to end products of the development process that satisfy the Guidelines.
Specific Design Guidelines 1. Any self-replicating device which has sufficient onboard information to describe its own manufacture should encrypt it such that any replication error will randomize its blueprint. 2. Encrypted MNT device instruction sets should be utilized to discourage irresponsible proliferation and piracy. 3. Mutation (autonomous and otherwise) outside of sealed laboratory conditions, should be discouraged. 4. Replication systems should generate audit trails. 10
5. MNT device designs should incorporate provisions for built-in safety mechanisms, such as: 1) absolute dependence on a single artificial fuel source or artificial "vitamins" that don't exist in any natural environment; 2) making devices that are dependent on broadcast transmissions for replication or in some cases operation; 3) routing control signal paths throughout a device, so that subassemblies do not function independently; 4) programming termination dates into devices, and 5) other innovations in laboratory or device safety technology developed specifically to address the potential dangers of MNT. 6. MNT developers should adopt systematic security measures to avoid unplanned distribution of their designs and technical capabilities.
PRESENT WORK IN NANOTECHNOLOGY : This quote from "The Next Big Thing Is Really Small: How Nanotechnology Will Change The Future Of Your Business" (by Jack Uldrich and Deb Newberry Read our review) sums it up nicely: "This is not to say that nanotechnology is a far-off, fuzzy, futuristic technology. It is not. It has already established a beachhead in the economy. The clothing industry is starting to feel the effects of nanotech. Eddie Bauer, for example, is currently using embedded nanoparticles to create stain-repellent khakis. This seemingly simple innovation will impact not only khaki11
wearers, but dry cleaners, who will find their business declining; detergent makers, who will find less of their product moving off the shelf; and stain-removal makers, who will experience a sharp decrease in customers. This modest, fairly low-tech application of nanotechnology is just the small tip of a vast iceberg--an iceberg that threatens to sink even the "unsinkable" companies." Nanotechnology in medicine research Nanotechnology is the latest buzzword in the technological circles. Nano particles are tiny in size and have their own calibrations. Nano particles range between the sizes of 1 to 100 nanometers. They are thousands of times smaller than the breadth of a human hair. In the field of medicine, nanotechnology is being used to study DNA molecules. In effect, these tiny particles form the middle path between bulky objects and particles of molecular and atomic sizes. Nanochannels are used to study different aspects and structure of the building blocks of the
Fig: nanodevice
human body. Cells are stretched and pushed through nanochannels to understand the working of a single cell. Nano-engineering is used to deliver drugs more effectively into the body at the cellular level. Massive research is being carried out to study the behavior of the tiniest particles, with the use of nanotechnology.
Nanotechnology in cancer treatments Nanotechnology is being considered as the most effective method to cure deadly cancer cells. Nanoparticles can penetrate into the tiny cancer cells and cause their destruction. Nanotechnology is being used to segregate cancer cells from healthy cells by using magnetic properties. The nanospheres can be used to effectively differentiate between different kinds of cancer cells like leukemia, breast cancer and prostate cancer. The biggest Fig: gold particles carrying anticancer drugs 12
benefit of using this cutting-edge technology is that cancer cells of the smallest concentration can be identified, which implies early detection of cancer and successful cure. Nanotechnology in metallurgy Metallurgy is the science of creating new materials such as alloys by combining properties of different metals or making modifications in the existing properties of metals. New metals, which are fabricated, contain better endurance and strength as compared to individual metals. Nanotechnology is being effectively used in making modifications at the atomic level to make materials more effective. Its use is extensive in processes such as catalysis. Nanotechnology in hydrology Water is a scarce resource with regard to growing contamination and population requirements. One of the best uses of nanotechnology is to clean contaminated and polluted water, thus saving millions of people from water borne diseases. Nanoparticles are used to coat filter papers and other water-cleaning agents to purify water to a greater degree by killing more number of disease causing bacteria than conventional water purifiers. The particles used in this process are nano silver particles. The process of water purification using nanotechnology is extremely cost effective, which makes it even more wonderful.
Nanotechnology for environment protection Accelerating amount of pollutants in the environment is not only destroying the health of people but also causing extinction of hundreds of living organisms. Air pollution from factories and industries is one of the major concerns all over the world. Nanotechnology is used to filter out the impurities in the air being released through the chimneys of industries. Refineries can reduce their level of pollution by implementation of this technology. What is more, the filtered pollutants that will be left over can be used for other industrial and construction purposes. This technology is also called green technology due to its environment friendly implications.
13
NANOTECHNOLOGY PRODUCTS: Nanocomposites Researchers at Pacific Northwest National Laboratory have developed a coating process to make sponge-like silica latch onto toxic metals in water. Self-Assembled Monolayers on Mesoporous Supports easily captures such metals as lead and mercury, which are then recovered for reuse or contained in-place forever. © PNNL One example of a SAMMS nanocomposite (Self-Assembled Monolayers on Mesoporous Supports). A plastic nanocomposite is being used for "step assists" in the GM Safari and Astro Vans. It is scratch-resistant, light-weight, and rust-proof, and generates improvements in strength and reductions in weight, which lead to fuel savings and increased longevity. And in 2001, Toyota started using nanocomposites in a bumper that makes it 60% lighter and twice as resistant to denting and scratching.
14
Fig: Electron micrograph of typical silicon nanocomposite cross section showing uniform distribution of conductive carbon nanotube network. Photo courtesy of U.S. Air Force.
Nanocrystals "Metal nanocrystals might be incorporated into car bumpers, making the parts stronger, or into aluminum, making it more wear resistant. Metal nanocrystals might be used to produce bearings that last longer than their conventional counterparts, new types of sensors and components for computers and electronic hardware. Nanocrystals of various metals have been shown to be 100 percent, 200 percent and even as much as 300 percent harder than the same materials in bulk form. Because wear resistance often is dictated by the hardness of a metal, parts made from nanocrystals might last significantly longer than conventional parts."
Fig: Quantum dots
Nanocrystals absorb then re-emit the light in a different color -- the size of the nanocrystal (in the Angstrom scale) determines the color. Six different quantum dot solutions are shown, excited with a long-wave UV lamp. Quantum dots are molecular-scale optical beacons. Qdot™ nanocrystals behave like molecular LEDs (light emitting diodes) by "lighting up" biological binding events with a broad palette of applied colors. The nanocrystalline coating of silver rapidly kills a broad spectrum of bacteria in as little as 30 minutes.
15
Fig: Nanocrystal
"Nanocrystals are an ideal light harvester in photovoltaic devices. (They) absorb sunlight more strongly than dye molecules or bulk semiconductor material, therefore high optical densities can be achieved while maintaining the requirement of thin films. Nanoparticles Stain-repellent Eddie Bauer Nano-CareTM khakis, with surface fibers of 10 to 100 nanometers, uses a process that coats each fiber of fabric with "nano-whiskers." Developed by Nano-Tex, a Burlington Industries subsidiary. Dockers also makes khakis, a dress shirt and even a tie treated with what they call "Stain Defender", another example of the same nanoscale cloth treatment. BASF's annual sales of aqueous polymer dispersion products amount to around $1.65 billion. All of them contain polymer particles ranging from ten to several hundred nanometers in size. Polymer dispersions are found in exterior paints, coatings and adhesives, or are used in the finishing of paper, textiles and leather. Nanotechnology also has applications in the food sector. Many vitamins and their precursors, such as carotinoids, are insoluble in water. However, when skillfully produced and formulated as nanoparticles, these substances can easily be mixed with cold water, and their bioavailability in the human body also increases. Many lemonades and fruit juices contain these specially formulated additives, which often also provide an attractive color. In the cosmetics sector, BASF has for several years been among the leading suppliers of UV absorbers based on nanoparticulate zinc oxide. Incorporated in sun creams, the small particles filter the high-energy radiation out of sunlight. Because of their tiny size, they remain invisible to the naked eye and so the cream is transparent on the skin. Sunscreens are utilizing nanoparticles that are extremely effective at absorbing light, especially in the ultra-violet (UV) range. Due to the particle size, they spread more easily, cover better, and save money since you use less. And they are transparent, unlike traditional screens which are white. These sunscreens are so successful that by 2001 they had captured 60% of the Australian sunscreen market.
16
Using aluminum nanoparticles, Argonide has created rocket propellants that burn at double the rate. They also produce copper nanoparticles that are incorporated into automotive lubricant to reduce engine wear. AngstroMedica has produced a nanoparticulate-based synthetic bone. "Human bone is made of a calcium and phosphate composite called Hydroxyapatite. By manipulation calcium and phosphate at the molecular level, we have created a patented material that is identical in structure and composition to natural bone. This novel synthetic bone can be used in areas where natural bone is damaged or removed, such as in the in the treatment of fractures and soft tissue injuries."
Nanostructured Materials Nanodyne makes a tungsten-carbide-cobalt composite powder (grain size less than 15nm) that is used to make a sintered alloy as hard as diamond, which is in turn used to make cutting tools, drill bits, armor plate, and jet engine parts. Kodak is producing OLED color screens (made of nanostructured polymer films) for use in car stereos and cell phones. OLEDs (organic light emitting diodes) may enable thinner, lighter, more flexible, less power consuming displays, and other consumer products such as cameras, PDAs,
laptops,
televisions,
and
other
as
yet
undreamt
of
applications.
Nanoclays and Nanocomposites Used in packaging, like beer bottles, as a barrier, allowing for thinner material, with a subsequently lighter weight, and greater shelf-life. $480B packaging and $300B plastics industries. Reduced weight means transportation costs decline. Changing from glass and aluminum - think beer and soda bottles - to plastic reduces production costs. Nanoclays help to hold the pressure and carbonation inside the bottle, increasing shelf life. It is estimated that beer in these containers will gain an extra 60 days (from 120 to 180) of shelf life, reducing spoilage, and decreasing overall costs to the end user. Nanocor is one company producing nanoclays and nanocomposites, for a variety of uses, 17
including flame retardants, barrier film (as in juice containers), and bottle barrier (as shown above). "They are not only used to improve existing products, but also are extending their reach into areas formerly dominated by metal, glass and wood." See Nanocor Nanocomposite Coatings Wilson Double Core tennis balls have a nanocomposite coating that keeps it bouncing twice as long as an old-style ball. Made by InMat LLC, this nanocomposite is a mix of butyl rubber, intermingled with nanoclay particles, giving the ball substantially longer shelf life.
Nanotubes Nanoledge makes carbon nanotubes for commercial uses, of which one mundane (marketing tactic) use is in a tennis racket, made by Babolat. The yoke of the racket bends less during ball impact,
improving
the
player's
performance.
Once companies like Nanoledge can scale-up their production from grams, to pounds, to tons, and can do so while controlling the type of nanotube they produce, the world becomes their oyster: everywhere strength and weight are a factor - such as in the aerospace, automobile, and airplane industries - they will make a major (disruptive) impact. Applied Nanotech recently demonstrated a 14" monochrome display based on electron emission from carbon nanotubes.
Nanocatalysts China's largest coal company (Shenhua Group) has licensed technology from Hydrocarbon Technologies that will enable it to liquify coal and turn it into gas. The process uses a gel-based nanoscale catalyst, which improves the efficiency and reduces the cost. One of the characteristic properties of all nanoparticles has been used from the outset in the manufacture of automotive catalytic converters: The surface area of the particles increases dramatically as the particle size decreases and the weight remains the same. A variety of chemical reactions take place on the surface of the catalyst, and the larger the surface area, the 18
more active the catalyst. Nanoscale catalysts thus open the way for numerous process innovations to make many chemical processes more efficient and resource-saving – in other words more competitive. Nanofilters Argonide Nanomaterials, an Orlando based manufacturer of nanoparticles and nanofiltration products, makes a filter that is capable of filtering the smallest of particles. The performance is due to it’s nano size alumina fiber, which attracts and retains sub-micron and nanosize particles. This disposable filter retains 99.9999+% of viruses at water flow rates several hundred times greater than virus-rated ultra porous membranes. It is useful for sterilization of biological, pharmaceutical and medical serums, protein separation, collector/concentrator for biological
warfare
detectors,
and
several
other
applications.
NANOTECHNOLOGY FUTURE: Today nanotechnology is still in a formative phase--not unlike the condition of computer science in the 1960s or biotechnology in the 1980s. Yet it is maturing rapidly. Between 1997 and 2005, investment in nanotech research and development by governments around the world soared from $432 million to about $4.1 billion, and corresponding industry investment exceeded that of governments by 2005. By 2015, products incorporating nanotech will contribute approximately $1 trillion to the global economy. About two million workers will be employed in nanotech industries, and three times that many will have supporting jobs. Descriptions of nanotech typically characterize it purely in terms of the minute size of the physical features with which it is concerned--assemblies between the size of an atom and about 100 molecular diameters. That depiction makes it sound as though nanotech is merely looking to use infinitely smaller parts than conventional engineering. But at this scale, rearranging the atoms and molecules leads to new properties. One sees a transition between the fixed behavior of individual atoms and molecules and the adjustable behavior of collectives. Thus, nanotechnology might better be viewed as the application of quantum theory and other nanospecific phenomena to fundamentally control the properties and behavior of matter. Over the next couple of decades, nanotech will evolve through four overlapping stages of industrial prototyping and early commercialization. The first one, which began after 2000, 19
involves the development of passive nanostructures: materials with steady structures and functions, often used as parts of a product. These can be as modest as the particles of zinc oxide in sunscreens, but they can also be reinforcing fibers in new composites or carbon nanotube wires in ultraminiaturized electronics.
Rearranging atoms leads to new properties. The second stage, which began in 2005, focuses on active nanostructures that change their size, shape, conductivity or other properties during use. New drug-delivery particles could release therapeutic molecules in the body only after they reached their targeted diseased tissues. Electronic components such as transistors and amplifiers with adaptive functions could be reduced to single, complex molecules. Starting around 2010, workers will cultivate expertise with systems of nanostructures, directing large numbers of intricate components to specified ends. One application could involve the guided self-assembly of nanoelectronic components into three-dimensional circuits and whole devices. Medicine could employ such systems to improve the tissue compatibility of implants, or to create scaffolds for tissue regeneration, or perhaps even to build artificial organs. After 2015-2020, the field will expand to include molecular nanosystems--heterogeneous networks in which molecules and supramolecular structures serve as distinct devices. The proteins inside cells work together this way, but whereas biological systems are water-based and markedly temperature-sensitive, these molecular nanosystems will be able to operate in a far wider range of environments and should be much faster. Computers and robots could be reduced to extraordinarily small sizes. Medical applications might be as ambitious as new types of genetic therapies and antiaging treatments. New interfaces linking people directly to electronics could change telecommunications. Over time, therefore, nanotechnology should benefit every industrial sector and health care field. It should also help the environment through more efficient use of resources and better methods of pollution control. Nanotech does, however, pose new challenges to risk governance as well. Internationally, more needs to be done to collect the scientific information needed to resolve the ambiguities and to install the proper regulatory oversight. Helping the public to 20
perceive nanotech soberly in a big picture that retains human values and quality of life will also be essential for this powerful new discipline to live up to its astonishing potential.
FUTURE PRODUCTS: In the world of "Star Trek," machines called replicators can produce practically any physical object, from weapons to a steaming cup of Earl Grey tea. Long considered to be exclusively the product of science fiction, today some people believe replicators are a very real possibility. They call it molecular manufacturing, and if it ever does become a reality, it could drastically change the world.
Fig: Replicator
Atoms and molecules stick together because they have complementary shapes that lock together, or charges that attract. Just like with magnets, a positively charged atom will stick to a negatively charged atom. As millions of these atoms are pieced together by nanomachines, a specific product will begin to take shape. The goal of molecular manufacturing is to manipulate atoms individually and place them in a pattern to produce a desired structure. 21
The first step would be to develop nanoscopic machines, called assemblers, that scientists can program to manipulate atoms and molecules at will. Rice University Professor Richard Smalley points out that it would take a single nanoscopic machine millions of years to assemble a meaningful amount of material. In order for molecular manufacturing to be practical, you would need trillions of assemblers working together simultaneously. Eric Drexler believes that assemblers could first replicate themselves, building other assemblers. Each generation would build another, resulting in exponential growth until there are enough assemblers to produce objects
Fig: Assembler
Assemblers might have moving parts like the nanogears in this concept drawing. Trillions of assemblers and replicators could fill an area smaller than a cubic millimeter, and could still be too small for us to see with the naked eye. Assemblers and replicators could work together to automatically construct products, and could eventually replace all traditional labor methods. This could vastly decrease manufacturing costs, thereby making consumer goods plentiful, cheaper and stronger. Eventually, we could be able to replicate anything, including diamonds, water and food. Famine could be eradicated by machines that fabricate foods to feed the hungry. Nanotechnology may have its biggest impact on the medical industry. Patients will drink fluids containingnanorobots programmed to attack and reconstruct the molecular structure of cancer cells and viruses. There's even speculation that nanorobots could slow or reverse the aging process, and life expectancy could increase significantly. Nanorobots could also be 22
programmed to perform delicate surgeries -- suchnanosurgeons could work at a level a thousand times more precise than the sharpest scalpel [source:International Journal of Surgery]. By working on such a small scale, a nanorobot could operate without leaving the scars that conventional surgery does. Additionally, nanorobots could change your physical appearance. They could be programmed to perform cosmetic surgery, rearranging your atoms to change your ears, nose, eye color or any other physical feature you wish to alter. What is MEMS Technology? Micro-Electro-Mechanical Systems, or MEMS, is a technology that in its most general form can be defined as miniaturized mechanical and electro-mechanical elements (i.e., devices and structures) that are made using the techniques of microfabrication. The critical physical dimensions of MEMS devices can vary from well below one micron on the lower end of the dimensional spectrum, all the way to several millimeters. Likewise, the types of MEMS devices can vary from relatively simple structures having no moving elements, to extremely complex electromechanical systems with multiple moving elements under the control of integrated microelectronics. The one main criterion of MEMS is that there are at least some elements having some sort of mechanical functionality whether or not these elements can move. The term used to define MEMS varies in different parts of the world. In the United States they are predominantly called MEMS, while in some other parts of the world they are called “Microsystems Technology” or “micromachined devices”. While the functional elements of MEMS are miniaturized structures, sensors, actuators, and microelectronics, the most notable (and perhaps most interesting) elements are the microsensors and microactuators. Microsensors and microactuators are appropriately categorized as “transducers”, which are defined as devices that convert energy from one form to another. In the case of microsensors, the device typically converts a measured mechanical signal into an electrical signal.
23
Over the past several decades MEMS researchers and developers have demonstrated an extremely large number of microsensors for almost every possible sensing modality including temperature, pressure, inertial forces, chemical species, magnetic fields, radiation, etc. Remarkably, many of these micromachined sensors have demonstrated performances exceeding those of their macroscale counterparts. That is, the micromachined version of, for example, a pressure transducer, usually outperforms a pressure sensor made using the most precise macroscale level machining techniques. Not only is the performance of MEMS devices exceptional, but their method of production leverages the same batch fabrication techniques used in the integrated circuit industry – which can translate into low per-device production costs, as well as many other benefits. Consequently, it is possible to not only achieve stellar device performance, but to do so at a relatively low cost level. Not surprisingly, silicon based discrete microsensors were quickly commercially exploited and the markets for these devices continue to grow at a rapid rate.
24
Fig: A surface micromachined electro-statically-actuated micromotor fabricated by the MNX. This device is an example of a MEMS-based microactuator.
The real potential of MEMS starts to become fulfilled when these miniaturized sensors, actuators, and structures can all be merged onto a common silicon substrate along with integrated circuits (i.e., microelectronics). While the electronics are fabricated using integrated circuit (IC) process sequences (e.g., CMOS, Bipolar, or BICMOS processes), the micromechanical components are fabricated using compatible "micromachining" processes that selectively etch away parts of the silicon wafer or add new structural layers to form the mechanical and electromechanical devices. It is even more interesting if MEMS can be merged not only with microelectronics, but with other technologies such as photonics, nanotechnology, etc. This is sometimes called “heterogeneous integration.” Clearly, these technologies are filled with numerous commercial market opportunities. While more complex levels of integration are the future trend of MEMS technology, the present state-of-the-art is more modest and usually involves a single discrete microsensor, a single discrete microactuator, a single microsensor integrated with electronics, a multiplicity of essentially identical microsensors integrated with electronics, a single microactuator integrated with electronics, or a multiplicity of essentially identical microactuators integrated with electronics. Nevertheless, as MEMS fabrication methods advance, the promise is an enormous design freedom wherein any type of microsensor and any type of microactuator can be merged with microelectronics as well as photonics, nanotechnology, etc., onto a single substrate.
25
Fig: A surface micromachined resonator fabricated by the MNX. This device can be used as both a microsensor as well as a microactuator.
26
HAZARDS OF NANOTECHNOLOGY:Hazards to Humans: In terms of liability cover, the insurance industry needs to know which nanoparticles are hazardous to humans, and what levels of concentration are required to cause harm. Can nanoparticles cause chronic health effects similar to asbestosis? The short answer is that we simply do not know.
Fig: out Types of hazards humans Initial investigations carried show sometonanoparticles are acutely toxic when compared to
larger particles composed of the same material, such as ultra-fine carbon and diesel exhaust particles respectively. Certain organs in mice have been shown to be adversely affected by some nanoparticles as well as significantly reduced offspring production in some aquatic life. If these effects are caused in other animals they may be possible in humans, though there have been no human studies to confirm this. Studies looking at the chronic effects of nanoparticles are much less common, though some are underway. The UK Council for Science and Technology highlighted that there is insufficient research into the toxicology, health and environmental effects of nanomaterials. This call has been taken seriously and there are now efforts to increase the amount of research into nanotoxicology. There are several ways that nanoparticles can enter the body. These include inhalation, ingestion, absorption through the skin and direct injection for medicinal purposes. Once the 27
particles are in the body they may be transported throughout the body before they are ejected, if at all. Inhalation of nanoparticles Particles breathed into the lungs can cause damage and scarring, which over long periods of exposure can lead to long term breathing difficulties. This is an analogous process by which asbestos fibres cause asbestosis. The fibres lodge deep within the lungs and trigger the local immune system, which sends specialised immune cells that try to digest the fibres and repair any damage by depositing new tissue. As the fibres are highly resistant, the immune cells cannot digest them, die off, cause more immune cells to attack the foreign body, and yet more tissue to be deposited. In some cases this can also cause the cells to become cancerous. Over many years of exposure this leads to thickening of the lung walls and reduces the amount of oxygen that can be absorbed from the air and decreases the amount of carbon dioxide that can be breathed out. This causes a shortness of breath and hence a reduced ability to perform any activities that require exertion and costly oxygen therapy may be required. Carbon nanotubes are potentially toxic to humans. Carbon nanotubes can be very similar to asbestos fibres; they are strong and can have a similar shape to asbestos fibres. There has been much research into the potential applications of nanotubes; however research into their toxicity is currently fragmented. Some studies refute any negative effects of carbon nanotubes, but several of the reviews conclude with statements similar to the following: “…carbon nanotubes are potentially toxic to humans and that strict industrial hygiene measures should to be taken to limit exposure during their manipulation”. Julie Muller et al. This statement was from a study that found carbon nanotubes cause inflammation in the lungs and scarring. This is a similar effect to asbestos exposure and gives clear indication that the potential risk from carbon nanotubes should be taken seriously. Titanium dioxide and carbon nanoparticles also show detrimental effects when inhaled. Carbon nanoparticles in this sense refer to a small cluster of carbon atoms and not in the form of tubes. Mice suffered inflamed lungs when exposed to these particles. One study by Tobias Stoeger et al showed that if the total surface area of all the particles of each dose was progressively 28
reduced, by using larger particles, a surface area threshold was found. Beyond this threshold, in effect if the particles became too large, no short term adverse effects were observed. While this is only one study it may indicate a safe level for short-term exposure to nanoparticles. Cerium oxide nanoparticles are added to some diesel fuels to reduce nitrogen oxide emissions and increase engine efficiency. Nitrogen oxide has been linked to acid rain and smog, and a reduction of this pollutant is an important goal for car manufacturers. Use of cerium oxide will release it into the atmosphere through car exhaust; and there are concerns that it may damage the lungs if inhaled and one study appears to lend weight to this theory. This is another nanotechnology where a debate is required to determine if the gain offered by the new technology outweighs the potential risks.
Absorption through skin Nanoparticles are being used in a number of products which are placed in direct contact with skin, including clothing, cosmetics and sun cream. Once absorbed through the skin if the nanoparticles come into contact with blood vessels they may behave in a similar way as if they had been ingested, namely collecting within certain organs or cells within the body. This again is another call to determine the toxicity of widely used nanoparticles.
Hazards to Environment: Removing nanoparticles from the environment may also present a significant problem due to their small size. Particles could conceivably be absorbed quickly into plants and soil or transported large distances in the air or suspended in water; and how do you filter out of the environment particles only a few atoms wide?
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Fig: Hazards to Environment
Hazards to aquatic life: Fish are susceptible to copper nanoparticles, which induce gill injury and acute lethality according to current research conducted with concentrations of 1.5 mg/litre. A fraction of the particles will dissolve to produce soluble copper, which is known to be toxic, but the toxic effects seen could not be explained solely by exposure to soluble copper. This implies the additional effects were cause because the copper was present on the nanoscale. Titanium dioxide nanoparticles have also been investigated but preliminary studies show that, while the particles do cause respiratory stress, it was not considered a major toxicant at the concentrations of one mg/litre. The carbon fullerene, C60, has also been shown to significantly reduce offspring production for freshwater shrimp which would have negative implications for populations of species further up the food chain.
Fig: Hazards to aquatic life CONCLUSION
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Nanotechnology is a growing field today. It has made true many possibilities of human life style. Many product from nanotechnology are very beneficial . In the near future this technology will come with new advancements in technical field. MEMS devices are revolutionary outcome of this field. But we have move forward with a thinking of sustainable development i.e. growing without harming the environment. Only then it will be proved as good technology.
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