Abstract:
The essence of nanotechnology is the ability to work at the molecular level, atom by atom, to create large structures with fundamentally new molecular organization. Compared to the behavior of isolated molecules, the behavior of structural features in the range of about 10-9 to 10-7 m (1,000 times smaller than the diameter of human hair) exhibit important changes. Nanotechnology is concerned with materials and systems whose structures and components exhibit novel and significantly improved properties.
These physical, chemical, and biological properties, processes and phenomena are novel due to their nanoscale size. The aim is to exploit these properties by gaining control of structures and devices at atomic, molecular, and supra-molecular levels and to learn to efficiently manufacture and use these devices. New behavior at the nanoscale is not necessarily predictable from that observed at large size scales. The most important changes in behavior are caused not by the order of magnitude size reduction, but by newly observed phenomena intrinsic to the nanoscale, such as size confinement, predominance of interfacial phenomena and quantum mechanics.
These physical, chemical, and biological properties, processes and phenomena are novel due to their nanoscale size. The aim is to exploit these properties by gaining control of structures and devices at atomic, molecular, and supra-molecular levels and to learn to efficiently manufacture and use these devices. New behavior at the nanoscale is not necessarily predictable from that observed at large size scales. The most important changes in behavior are caused not by the order of magnitude size reduction, but by newly observed phenomena intrinsic to the nanoscale, such as size confinement, predominance of interfacial phenomena and quantum mechanics.
Once it is possible to control feature size, it is also possible to enhance material properties and device functions beyond those that are considered feasible. Reducing the dimensions of structures leads to entities, such as carbon nanotubes, quantum wires and quantum dots, thin films, DNA-based structures, and laser emitters, which have unique properties. Such new forms of materials and devices herald a revolutionary age for science and technology, provided the underlying principles can be discovered and fully utilized.
Introduction:
Nanotechnology may be defined as “Research and technology development at the atomic, molecular and macromolecular levels in the length scale of 1–100 nanometer range, to provide a fundamental understanding of phenomena and materials at the nanoscale and to create and use structures, devices and systems that have novel properties and functions because of their small size.” Nanometer is one billionth of a meter – a scale at which Hydrogen and carbon atoms appear as large as baseballs. Now imagine picking up those atoms and building a machine. In other words, nanotechnology is about building things atom-by-atom, molecule-by-molecule.
The concept of nanotechnology was founded by Richard Feynman in 1959 through his famous lecture, “There is Plenty of Room at the Bottom”. He envisioned that if one could fabricate materials and devices at the molecular scale, a new class of miniaturized instrumentation would be needed to manipulate and measure the properties of these small nano structures. It was not until the 1980s that instruments were invented with the capabilities Feynman envisioned. These instruments, including scanning tunneling microscopes, atomic force microscopes, and near-field microscopes, provide the capabilities for nanostructure measurement and manipulation. Modern computational capabilities enable sophisticated simulations of material behavior at the nanoscale.
The Goal of Nanotechnology:
The goal of nanotechnology is to build tiny devices called nanomachines. To build things on such a small scale, one has to be able to manipulate atoms individually. The change of nanotechnology is to place atoms precisely where one wishes them on a structure. Research in chemistry, molecular biology and scanning probe microscopy is laying the foundations for molecular machine systems. The molecular machines are working in our body right now, for example, a protein in human body. It is like a machine that moves molecules. This is basically an oxygen pump used in red blood cells. The heat of other molecules around it powers it. A channel opens periodically to the center of the protein, allowing oxygen to pass from the outside and bind with iron for transport through out the body. Scientists can now construct natural proteins and even synthesizes new ones with novel properties never seen in nature. With enough understanding, proteins may be turned into microscopic tools to do the required jobs.
Limitations to Overcome:
All the products around us are made of atoms. The properties of these products depend on how their atoms are arranged. By rearranging the atoms of coal could be turned into diamond. Rearranging the atoms in sand and adding a few other trace elements could make computer chips. Today’s manufacturing methods are very crude at the molecular level. Casting, grinding, milling and even lithography move atoms in great thundering statistical herds. It is like trying to make things out of LEGO blocks with boxing gloves on hands. The LEGO blocks could be heaped and piled up, but fine objects cannot be created like this. Nanotechnology removes the boxing gloves and enables to snap together the fundamental building blocks of nature easily, inexpensively and in most of the ways permitted by the laws of physics.
Expansion of Computational Capability:
Expansion of computational capability now enables sophisticated simulations of material behavior at the nanoscale. Nanotechnology will lead to the revolution in computer hardware and it would be possible to fabricate a new of products that are cleaner, stronger, lighter, more precise, and efficient and billions of times faster. Post–lithographic manufacturing technology will allow to inexpensively build computer system with quantities of logic elements that are molecular in both size and precision and are interconnected in complex and
Highly idiosyncratic patterns.
Nanotechnology would permit the manufacture of a large number of small devices, each able to analyze a small volume. Given enough such devices operating in parallel, larger volumes could be analyzed and the information from many individual devices integrated to provide a coherent picture of the larger whole. Effective use of this option will require massive computational power – which will also be made feasible with nanotechnology. Estimates of the computational power that should be provided by nanotechnology exceed 1024 logic operations per second for a single desktop computer. This amount of raw computational power should make control of a large number of parallel devices feasible, and should permit integration and analysis of the information so obtained.
Self-replication at Nano-scale:
Computer reproduces information at almost no cost. A trend is underway to invent devices that manufacture at almost no cost, by treating atoms discretely, like computer treat bits of information. This would allow automatic construction of consumer goods without traditional labour, like a photocopying machine produces unlimited copies without a human retyping the original information.
Miniaturization leads to tools capable of manipulating individual atoms, like protein in a potato manipulating the atom of soil, air and water to make copies of it. Nanotechnology, the marriage of chemistry and engineering is ushering in the era of self-replicating machinery and self–replicating consumer goods. It proposes the construction of novel molecular devices possessing extraordinary properties. The trick is to manipulate atoms individually and place them exactly where needed to produce the desired structure. In such a way millions of terabytes of RAM can be produced quite inexpensively, though the cost of designing may be high. Working at the resolution of the limit of the matter, it will enable the ultimate in miniaturization and performance.
Applications of Nanotechnology:
The early goal of nanotechnology is to produce a nano-size robotic arm capable to manipulate atoms and molecules into useful products. Molecule manufacturing merges computer controlled self-replicating systems with atomically precise structural modifications. This would let us create a low cost manufacturing technology able to build any product including fast computing machines with atomic precision. The assembler nano-machine could be made to make copies of it and those copies could make their copies. So the object could be assembled quickly by trillions of nano supercomputers working in parallel. If the device is built atom by atom to fit perfectly together in a sealed environment so that no stray atoms land and never stress beyond bonding strength, the device will never wear out.
Some of most dramatic changes are expected in medicine. Scientists envision machines cleaning the arteries as they travel through the circulatory system, tracking down and destroying cancerous cells and tumors, and repairing injured tissues at the site of the wound and even replacing the missing limbs or damaged organs.
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Figure 1: Nanorobot embedded in a growing clot with red cell
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Figure 2: Bloodbome nano brobots
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| Figure 3: Foglet |
Nanotechnology promises to make lives healthy and wealthy and it will be able to do so without consuming natural resources or spewing pollution into the environment. Nanotechnology will touch our lives right down to the water we drink and the air we breathe. Once the ability to capture, position and change the configuration of a molecule is acquired, it would be possible to create filtration systems that will scrub the toxins from the air or remove hazardous organisms from the potable water.
Self-replicating systems have long been seen as an economical method of exploring space. It is expected that the costs involved in space exploration using self-replicating probes would drop dramatically. With the current cost of transporting payloads into space being very high as $20,000 per Kg, little is being done to take the advantage of space. Nanotechnology will help to deliver more machines of smaller size and greater functionality into space, paving the way for solar system expansion. The medical application of nanotechnology might even allow us to adapt our body for survival in space. Nano-machines like nano-robots and nano-tubes find immense utility in various fields of medical and technological research.
Information Processing in Utility Fog:
Using nanotechnology we can design an intelligent polymorphic material that, like human body, consists of trillion of microscopic ` but act in accordance with patterns of global information. Unlike our cells, they will reprogram more quickly and more widely, adopt a wider array of functions. The particular scheme for this intelligent material is called ‘utility fog’. Utility fog consists of a mass of tiny robots. Unlike water fog, they do not float in the air but from a lattice by holding hands in twelve directions. Each robot has a fairly small body compared to its arm spread, and the arms are relatively thin. Each arm is telescoping – an action driven by a relatively powerful motor- and can be waved back and forth by relatively weak motors. A utility fog with fewer arms is called foglet shown in fig 3.
Nano-electronics and Computer Technology:
The Semiconductor Industry Association (SIA) has developed a roadmap for continued improvements in miniaturization, speed, and power reduction in information processing devices-sensors for signal acquisition, logic devices for processing, storage devices for memory, displays for visualization, and transmission devices for Communication. The SIA roadmap projects the future to approximately 2010 and to 0.1micron (100nm) structures. The area of magnetic information storage is illustrative. Within 10 years of the fundamental discovery of the new phenomenon of giant magneto resistance, this nanotechnology completely replaced older technologies for disk computer heads. Other potential breakthroughs include nano-structured microprocessor devices that continue the trend in lower energy use and cost per gate, thereby improving the efficacy of computers by a factor of millions. Communications systems with higher transmission frequencies and more efficient utilization of the optical spectrum to provide at least ten times more bandwidth, with consequences in business, education, entertainment, and defense. Small mass storage devices with capacities at multi-terabit levels, a thousand times better than today; and integrated nano-sensor systems capable of collecting, processing, and communicating massive amounts of data with minimal size, weight, and power consumption. Potential applications of nano-electronics also include affordable virtual reality stations that provide individualized teaching aids; computational capability sufficient to enable unmanned combat and civilian vehicles.
Miniaturization of Computing Machines:
The only major breakthrough necessary to build the fog is nanotechnology it self. Assemblers need to build molecule-size, individually controllable, physical actuators, arms, motors, gears, sprockets, pulleys and the like, and then molecular-size computers to control them. The ultimate in miniaturization of the circuitry of computing machines would be circuit elements made out of small assemblies of atoms or molecules (molecular electronics). The first step on this road is to study the properties of atomic wires, which are nothing but short chains of atoms that conduct electricity between two contacts. Researchers have performed calculations on both metallic and covalently bonded atomic wires connecting two metal electrodes.
Carbon nanotubes:
Carbon nanotubes are the basic material for constructing the electronic devices of nano-size. It is expected that accuracy, efficiency and extremely small size of these devices will be responsible for replacing all electronic devices to nano carbon devices. It is being claimed that one day the Silicon Valley may turn into carbon valley. Carbon nanotubes were first synthesized and characterized in later 1991. The novel material contained a wide variety of multiwalled nanotubes (MWNT) containing 2-50 concentric cylindrical graphene sheets with a diameter of a few nanometers and a length of up to 1 μm. It was produced at the negative electrode of an arc discharge and appeared to be mixed with a large amount of other forms of carbon. This encouraged many groups throughout the world to produce and purify nanotubes. It has already been realized that nanotubes have unique electronic and mechanical properties that could lead to ground breaking industrial applications. How ever, resistance is a serious problem when building electric circuit on small scale. If we build a circuit on a small scale, its natural frequency goes up but the skin depth only decrease with the square root of the scale ratio, and therefore resistance is quite a big problem. Possibly, we can beat resistance through the use of super conductivity if the frequency is not too high.
Nanotube field-effect transistor:
Transistors are the basic building blocks of integrated circuits. To use nanotubes in future circuits it becomes essential to be able to make transistors from them. Nanotube transistors, using individual multi-wall or single- wall nanotubes as the channel of a field-effect transistor (FET), have been fabricated and tested successfully.
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| Figure 4: Nano tube FET |
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| 5: Output Characteristics of FET |
While measuring the electrical characteristics of nanotube-FETs it is found that the amount of current (ISD) flowing through the nanotube channel can be changed by a factor of 100,000 by changing the voltage applied to gate (VG), as seen in the graph (figure 5). G is the low bias conductance of the tube.
As the FET is cooled down from room temperature to 4 Kelvin (minus 460 degree Fahrenheit) the device behavior changes dramatically. While the device acts like a field-effect transistor at room temperature, at 4K it behaves like a single-electron transistor (SET). The three plots above (red, blue and purple) show this change in device behavior for different temperatures.
Health and Medicine:
Living systems are governed by molecular behavior at nanometer scales where the disciplines of chemistry, physics, biology, and computer simulation all now converge. Such multidisciplinary insights will stimulate progress in nano biotechnology. The molecular building blocks of life—proteins, nucleic acids, lipids, carbohydrates and their non-biological mimics-are examples of materials that possess unique properties determined by their size, folding, and patterns at the nanoscale. Recent insights into the uses of nano fabricated devices and systems suggest that today’s laborious process of genome sequencing and detecting the genes’ expression can be made dramatically more efficient through utilization of nano fabricated surfaces and devices. Expanding our ability to characterize an individual’s genetic makeup will revolutionize the specificity of diagnostics and therapeutics. Beyond facilitating optimal drug usage, nanotechnology can provide new formulations and routes for drug delivery, enormously broadening their therapeutic potential. Increasing nano- technological capabilities will also markedly benefit basic studies of cell biology and pathology. As a result of the development of new analytical tools capable of probing the world of the nanometer, it is becoming increasingly possible to characterize the chemical and mechanical properties of cells (including processes such as cell division and locomotion) and to measure properties of single molecules. These capabilities thus complement (and largely supplant) the ensemble average techniques presently used in the life sciences.
Moreover, biocompatible, high- performance materials will result from controlling their nanostructure. Proteins, nucleic acids, and lipids, or their non-biological mimics, are example of materials that have been shown to possess unique properties as a function of their size, folding, and patterns. Based on these biological principles, bioinspired nano systems and materials are currently being formed by self-assembly. Artificial inorganic and organic nanoscale materials can be introduced into cells to play roles in diagnostics (e.g., quantum dots in visualization), but also potentially as active components. Finally, nanotechnology-enabled increases in computational power will permit the characterization of macromolecular networks in realistic environments. Such simulations will be essential in developing biocompatible implants and in the drug discovery process [6]. Potential applications include rapid, more efficient genome sequencing enabling a revolution in diagnostics and therapeutics; effective and less expensive health care using remote and in vivo devices; new formulations and routes for drug delivery that enormously broaden their therapeutic potential by targeting the delivery of new types of medicine to previously inaccessible sites in the body;
More durable rejection-resistant artificial tissues and organs;
Enable vision and hearing aids; and
Sensor systems that detect emerging disease in the body, which will ultimately shift the focus of patient care from disease treatment to early detection and prevention.
Retina Implants:
Retinal implants are in development to restore vision by electrically stimulating functional neurons in the retina. One approach being developed by various groups including a project at Argonne National Laboratory is an artificial retina implanted in the back of the retina. The artificial retina uses a miniature video camera attached to a blind person’s eyeglasses to capture visual signals. The signals are processed by a microcomputer worn on the belt and transmitted to an array of electrodes placed in the eye. The array stimulates optical nerves, which then carry a signal to the brain.
Nanomedicine:
The nanotechnology promises many applications in the field of Materials and Manufacturing, Nano-electronics and Computer Technology, Health and Medicine, Aeronautics and Space Exploration, Environment and Energy, National Security, Drug Delivery Systems, Water Purification and Desalinization. Drug delivery systems are being designed using nano-particles to deliver medicine to specific parts of the body, for example to tumours. An illustration of how nano-machines interact with the cells in the body, to deliver drug, detect infections and carry out other roles in the field of nanomedicine. Nanites inspecting red blood cells are shown in figure 6. The ultimate aim is to create a nano-shell (figure 7), full of medicine that is strong enough to journey through the body until triggered to release its contents. Nano-shells are about 1/20th the size of a red blood cell, and are about the size of a virus. They are ball-shaped and consist of a core of silica covered by a metallic shell, either gold or silver. Nano-shells are already being developed for applications including cancer diagnosis, cancer therapy, and diagnosis and testing for proteins associated with Alzheimer's disease, and drug delivery. Nano-shells allow the absorption of energy and then create an intense heat that kills the tumor cells.
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Figure 6: Nanites inspecting
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Figure 8: Nano Shells kills the tumour
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| Figure 7: Nano- Shells |
Nanotechnology provides a wide range of new technologies for developing customized solutions that optimize the delivery of pharmaceutical products. To be therapeutically effective, drugs need to be protected during their transit to the target action site in the body while maintaining their biological and chemicals properties. Some drugs are highly toxic and can cause harsh side effects and reduced therapeutic effect if they decompose during their delivery. Depending on where the drugs will be absorbed (i.e. colon, small intestine, etc), and whether certain natural defense mechanisms need to be passed through such as the blood-brain barrier, the transit time and delivery challenges can be greatly different. Once a drug arrives at its destination, it needs to be released at an appropriate rate for it to be effective. If the drug is released too rapidly it might not be completely absorbed, or it might cause gastro-intestinal irritation and other side effects.
The drug delivery system must positively impact the rate of absorption, distribution, metabolism, and excretion of the drug or other substances in the body. In addition, the drug delivery system must allow the drug to bind to its target receptor and influence that receptor's signaling and action, as well as other drugs, which might also be active in the body. Drug delivery systems also have ever restrictions on the materials and production processes that can be used. The drug delivery material must be compatible and bind easily with the drug, and be bio-resorbable. The production process must respect stringent conditions on processing and chemistry that would not degrade the drug, and still provide a cost effective product.
Nano terrorism “The Right tools in wrong hands”:
As with computers, nanotechnology and programmable assembler could become ordinary household objects. It is not too likely that the average person will get hold of and launch a nuclear weapon, but imagine a separatist launching an army of nanorobots programmed to kill on the basis of racial discrimination or sharp philosophical differences. Vast armies of tiny, specialized killing machines that could be built and dispatched in a day; nanosized surveillance devices or probes that could be implanted in the brain of people without their knowledge.
A small nano-machine capable of replication, could copy itself too many times. If it were capable of surviving outdoors, and of using biomass as raw material, it could severely damage the environment. An effective means of sabotage would be to release a hard-to-detect robot that continued to manufacture copies of it by destroying its surroundings. Destructive nano-machines could do immense damage to unprotected people and objects. If the wrong people gained the ability to manufacture any desired product, they could rule the world, or cause massive destruction in the attempt. Certain products, such as vast surveillance networks, powerful aerospace weapons, and microscopic antipersonnel devices, provide special cause for concern.
Further Possible Application:
1) To cure skin diseases, a cream containing nanorobots may be used. It could remove the right amount of dead skin, remove excess oils, add missing oils, apply the right amounts of natural moisturizing compounds, and even achieve the elusive goal of ‘deep pore cleaning’ by actually reaching down into pores and cleaning them out. The cream could be a smart material with smooth–on, peel–off convenience.
2) A mouthwash full of smart nanomachines could identify and destroy pathogenic bacteria while allowing the harmless flora of the mouth to flourish in a healthy ecosystem. Further, the device would identify particles of wood, plaque, or tartar, and lift them from teeth to be rinsed away. Being suspended in liquid and able to swim about, devices would be able to reach surfaces beyond reach of toothbrush or the fibres of floss. As short lifetime medical nano-devices, they could be built to last only a few minutes in the body before falling apart into materials of the sort found in foods (such as fibre).
3) Medical nano-devices could augment the immune system by finding and disabling unwanted bacteria and viruses. When an invader is identified, it can be punctured, letting its contents spill out and ending its effectiveness. If the contents were known to be hazardous by themselves, then the immune machine could hold onto it long enough to dismantle it more completely.
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