ABSTRACT

Nanotechnology, the short gun marriage of chemistry and engineering in molecular manufacturing or more simply, building things one atom or molecule at a time with programmed nanoscopic robot arms. This technology proposes the construction of novel molecular devices possessing extraordinary devices by manipulating atoms individually and placing them exactly where needed to produce the desired result. In this paper the two fundamental different approaches to nanotechnology are clearly explained including the two main concepts of the technology and differentiated those two concepts. Carbon tubes, which are the heart for this technology, is highlighted which possesses extraordinary physical and chemical properties because of which it is possible to make incredible components. The importance of nanotube transistors in making new class of smaller, faster and lower power consumed computer chips is illustrated. In this text proofs for the existence of nanotechnology in the present world are given. It is clearly described with neat and realistic figures how this technology has been a break through in all fields especially in computers and electronics. This presentation also emphasized on the prominent role played by this elegant technology in making several comfortable, tiny and easily operatable components. Finally, the latest developments taken place in the world are exemplified, ending with an interesting conclusion about the performance of this technology in the future.

INTRODUCTION:

Imagine a technology so powerful that it will allow such feats as desktop manufacturing, cellular repair, artificial intelligence, inexpensive space travel, clean and abundant energy and environmental restoration; a technology so portable that every one can reap its benefits; a technology so fundamental that it will radically change the economic and political systems; a technology so imminent that most of people will see its impact within the lifetimes. Such is the promise of nanotechnology.

Albert Einstein first proved that each molecule measures about a nanometer (a billionth of a meter) in diameter. In 1959, it was Richard P. Feynman who predicted a technological world composed of self-replicating molecules whose purpose would be the production of nano-sized objects. Almost a hundred years after Einstein’s insight and 40 years after Feynman’s initial proposition, the nanometer scale looms large on the research agenda. The semiconductor industry is edging closer to the world of nanotechnology where components are miniastured to the point of individual molecules and atoms. A push is well underway to invent devices that will manufacture anything at almost no cost, by treating atoms discretely, like computers treat bits of information. This would allow automatic construction of consumer goods without traditional labour, like a Xerox machine produces unlimited retyping the original information. Electronics is fuelled by miniasturisation. Working smaller has led to the tools capable of manipulating individual atoms, just as the proteins in a potato manipulate the atoms of soil, water and air to make copies of themselves. The shotgun marriage of chemistry and engineering called nanotechnology is ushering in the era of self replicating machinery and self-assembling consumer goods made from cheap raw atoms.

WHAT IS NANOTECHNOLOGY?

Nanotechnology is molecular manufacturing or, more simply building things one atom or molecule at a time with programmed nanoscopic robot arms. A nanometer is one billionth of a meter (3 to 4 atoms wide). Utilizing the well-understood chemical properties of atoms and molecules (how they stick together) a nanotechnology 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. Nanotechnology broadly refers to the manipulation of matter on the atomic and molecular scales i.e. where the objects of interest are 0.1-100 nanometer n size. Atomic diameters represent the lower end of this range at tenths of nanometers. Transistors used in the present generation of microprocessors, with dimensions of the order of 100 nanometers are at the upper end of the nanotechnology range. As atoms come together to form molecules and molecules come together to form clusters or crystals, the inherent macro-scale properties are determined. By controlling molecular structure in material synthesis, mankind has gained unprecedented control over the basic material properties such as conductivity, strength, capacity, ductility and reactivity, yielding innovative applications ranging from batteries to automotive materials. This is a passive nano technique that primarily focuses on tuning the properties of resulting bulk materials. The active nano technique facilitates creation of functional electronic and ultimately mechanical devices at the nano scale.

At nano-scale, different laws come into play. Properties of traditional materials change and the behaviour of surfaces starts to dominate the behaviour of bulk materials, opening up new realms. In the electronic domain, the benefit of working on nano-scale is production of smaller things. Using nanotubes or other molecular configurations enables engineers to break through this barrier in the semiconductor industry, which is expected to provide even smaller circuits and even more powerful computers, by working below the wavelength of light, X-ray; etc. The ultimate result is circuit elements consisting of single molecules.

By treating atoms as discrete, bit-like objects, molecular manufacturing will bring a digital revolution to the production of material objects. Working at the resolution limit of matter, it will enable the ultimate in miniaturization and performance. By starting with cheap, abundant components---molecules and processing them with small, high frequency, high productivity machines, it will make products inexpensive. Design computers will each execute more instructions per second than the entire semiconductor CPU’s in the world.

APPROACHES OF NANOTECHNOLOGY:

The two fundamentally different approaches to nanotechnology are graphically termed ‘top-down’ and ‘bottom-up’. Top down refers to making nanoscale structures by machining and etching techniques, whereas bottom-up, or molecular nanotechnology, applies to building organic and inorganic structures atom-by-atom, or molecule-by-molecule. Top–bottom or bottom-up is a measure of the level of advancement of nanotechnology. Nanotechnology, as applied today, is still mainly at what may be considered the more primitive bottom-top stage, building upward in the Molecular scale as shown in the below figure.

CONCEPTS OF NANOTECHNOLGY:

There are two concepts commonly associated with nanotechnology:

1. Positional Assembly

2. Self-Replication

Clearly, we would be happy with any method that simultaneously achieved the following three objectives. However, this seems difficult without using some form of positional assembly (to get the right molecular parts in the right places) and some form of self-replication (to keep the costs down).

1. Get essentially every atom in the right place.

2. Make almost any structure consistent with the laws of physics and chemistry that we can specify in atomic detail.

3. Have manufacturing costs not greatly exceeding the cost of the required raw materials and energy.

TOOLS OF NANOTECHNOLOGY:

The icons of this revolution are scanning probe microscopes—the scanning tunneling microscope (STM) and the atomic force microscope (AFM). Both these machines have the ability to interact with materials at the molecular level, although this is limited. They are capable of creating pictures of individual atoms or moving them from place to place.

Researches at Cornell University created the world’s smallest guitar carved out of crystalline silicon and world’s smallest car using an atomic force microscope (AFM).

Drexler has proposed the Assembler, a nanosize mechanical machine, which could manipulate atoms precisely. These machines could be told to build anything. To control these miniature run-abouts, Drexler has designed the nanocomputer. This is not an electronic device but one that would work on ‘rod-logic’; a system of criss-crossing mechanically-operated rods interacting with each other. These computers would be small, typically fitting inside a 400-nanometer cube, which is approximately 1000 times smaller in volume than one human cell. However, these would be as powerful as some of today’s desktop computers.

CARBON NANOTUBES (Key role in Nano Technology):

In 1991, carbon nanotube was discovered from the cathode product in carbon-arc discharge method similar to that used for fullerenes preparation. This discovery opened a new chapter both in nanotechnology and in carbon chemistry.

Because of their nano scale size and particular structure, carbon nanotubes exhibit following novel electronic, mechanical and chemical properties.

The average E value from the experiments of tubes was around 1.28 TPa with no dependence on tube diameter, which is similar to the in-plane modulus of graphite, 1.06 TPa; the largest of any known bulk material. (for steel, the E value is around 200 GPa).

Based on their unique properties, carbon nanotubes are expected to have variety of applications. A lot of research has been carried out on synthesis, characterization, property measurement and applications of carbon nanotubes and will be continued. The structure of nano tubes can be seen as shown.

The high stiffness, coupled with the low density for nanotubes, implies that nanotubes might be useful as nanoscale fibres in strong, lightweight composite materials.

The researchers have built the world’s first array of transistors out of carbon nanotubes—tiny cylinders of carbon atoms that measure as small as 10 atoms across and are 500 times smaller than today’s silicon-based transistors. The breakthrough is a new batch process for forming large numbers of nanotube transistors, which is essential for future mass production. Some types of those transistors can be seen in below figure.

These are pentacene thin film transistors which are photo lithographically fabricated on flexible polymide film.

REAL-WORLD NANO EXISTS:

Given Imaging, an Israel company, has developed a pill-size video camera that can travel through the digestive track and transmit pictures along the way, providing a less invasive technique to examine the small intestines. This video camera uses a miniature CMOS video imaging chip and white LED as a light source.

In 1998, Israeli scientists demonstrated that DNA could be coated with silver and made to conduct electricity. They predicted that the ability of DNA to organize itself into complex patterns and copy these patterns precisely over again and again would render such life molecules to develop into electronic molecules.

NANOMECHANICAL COMPUTATIONAL SYSTEMS:

The positioning systems in molecular assemblers need devices to direct their programmed movements and ways to store these programs. Computers and control systems similar to those already devised for macroscale robotic arms can be implemented at the molecular level. At the current rate of development, molecular electronic computers that would be used for this purpose will likely be commercialized well before the robot arms.

The following Drexler’s analysis of a molecular mechanical computer provides what is essentially a lower bound to the performance of a computer that could be built, given replicating assembler systems:

· Switching times are on the order of 0.1ns;

· Combinational logic systems can achieve for register to register transfers in 1.2ns;

· Nanomechanical reduced instruction set computer(RISC) machines can achieve clock speeds of 1GHz, executing instructions at 1000MIPS(million of instructions per second);

· A forced convection system with fractal plumbing could effectively remove about 100KW from a 1cm cube at 273K. This would allow 10¹² CPU scale systems with million transistors each to operate with in that volume.

This 10¹² CPU system would run at about 10¹⁵ MIPS. By comparison, personal computers run at about 5-20MIPS, engineering workstations run at about 200plus MIPS, supercomputers run at about 1lakh MIPS and the human brain runs at 1crore MIPS. So one of these machines would have the computational equivalent of a million human brains in the volume of a cubic centimeter (in terms of logic operations per second; programming is another matter). Fast molecular tape memory similar to RNA is also possible. It would have a storage density on the order of 5*10²¹ bits per cubic centimeter. That density is sufficient enough to store the information content of the library of congress within the dimensions of a office sheet paper.

SUPER-FAST CHIPS:

Harvard university engineers have developed faster and smaller chips using tiny crystal rods of silicon and other semiconductors. The semiconductor rods were sliced onto chips to form rudimentary circuits that perform logic operations. These rods, or nanowires, are easier to be manipulated into miniature sizes for producing super fast chips. These chips were built from individual atoms. Out of a droplet of solvent saturated with silicon or gallium nitride the researchers were able to grow perfect rod shaped sub-miniature crystals.

A solution containing nanowires is squirted onto a silicon-oxide wafer. A chemical on the wafer guides the wires to the right place. Each intersection where one nanowire crosses another acts like a transistor, which is much smaller than the tens of millions of transistors in current computer chips. These transistors are essentially voltage-controlled switches. The nanowires can be wired together to perform basic logic operations needed for computations. To build a dense circuitry, the nanowires need to be moved closer.

Practical computer chips using nanowires are likely to be developed in the near future. Dr Lieber reveals that in a year or two, such nanowire transistors could be used as biological sensors by attaching them to specific molecules. A piece of anthrax can be bound to the nanowires. Since DNA and proteins carry electrical charges, these could switch the transistors on, setting off an alert.

NANOTECHNOLOGY, A BREAK THROUGH IN ALL FIELDS:

Nanotechnology has been successful in almost all the fields irrespective of its kind and with the help of this technology it is possible to perform any type of operations starting from manipulating the molecules for separating impurities to the stage where it is the easy method for the production of power.

In molecular manufacturing systems, using nanotechnology it is possible transform raw materials, in molecular form, into finished products. Impurities could be separated from feedstock molecules using a sorting rotor which can be seen as in the figure.

The purified molecules can be transported away from the sorter system using the molecular equivalent of a conveyor belt. Once a conveyor belt, the molecules can be transported to other belts, changing speed or frequency if necessary. The estimated belt speed is 0.5cm/s and the transition time form belt to belt is less than 0.2µs. a system for transforming a stream of small feedstock molecules into a stream of reagent moieties would be between one million and three million atoms in size. It could deliver the equivalent of its own mass is about 3 sec. The error is rated to be less than 1in 10¹⁵ operations at 10⁶ operations per second. This gives a mean time to failure of about 3000 years. Other possible scheme has reagent moieties transported up through the centre of a hollow manipulator arm to a working tip for positional synthesis. Drexler has analyzed one such device as shown.

The device shown in the above figure has arms design stiffness of 25N/m helps to hold positional errors to below one in 10¹⁵. Applying 1nN of force at the tip would deflect the arm only 0.04nm. The net result of this device is that it uses a cheap fuel such as acetone, weighs one KG, can produce high purity products at a rate of 1Kg/Hr, has a waste product of high purity water and generates excess power along with waste heat from release of energy from feedstock molecules.

Below figures shows the possibility for the production of compact power generation using nanotubes which are very productive even from the commercial side.

Nano technology is also playing an important role for electronic displays so as replace existing CRO and CRT’s and it is even competing with LCD (Liquid Crystal Display) which is the advanced trend in electronic displays.

The process involved for electronic display using nanotubes is as follows:

• Firstly, Mixture of C₆₀ and nickel is ‘steered’ to specific surface sites by evaporating through a mask. The mask has an array of holes of 300 nm and can be moved with a precision of 1 nm.

• The C₆₀/nickel mixture is evaporated sequentially in ultra high vacuum so as to form alternating layers of C₆₀ and nickel with no impurities

• Then heat it up in the presence of a magnetic field. In this step, the C₆₀ molecules are transformed into bundles of perfectly aligned nanotubes.

LATEST DEVELOPMENTS:

At this year’s International Electron Devices meeting, there will be presentations from Japan’s NTT DoCoMo engineers that will describe transistors that can be used switched on and off based on the movement of a single electron. Lucent Technologies researchers will present a data storage technology concept in which information is stored in an aerosol of floating crystals as small as three nanometers, or three-billionths of a metre, in diameter. Quantum Logic devices is developing sensors to detect substances at levels too low to be found by existing methods. Such sensors could be used, for example, to diagnose diseases sooner than is now possible.

WHEN WILL NANOTECHNOLOGY ARRIVE?

‘Arrive’ is broadly defined as the arrival of the first ‘universal assembler’ that has the ability to build with single atoms anything one’s software defines. A universal assembler may look like a microwave oven, connected to raw atomic feed stock, like carbon black, oxygen, sulphur powder etc. Other portable assemblers would extract atomic feed stock out of the air and soil. The assembler would make Dock Martins as easily as it would make a supercomputer or a pizza.

With the researches which are going on in the labs as shown a period of 8 to 15 years seems to be the best guess estimate. As more people from all walks of life learn of the nanotechnology concept and add their talents to the quest, you can be sure that research will accelerate and the time frame will shorten. How long will it take for paradise to arrive on earth and in space after the universal assembler is invented? Not too long, we hope.

TO HIT THE ROAD AHEAD:

Progress in the 21^st century will be 1000 times greater than in the 20^th century in terms of technical change. Around 2030, we should be able to flood our brains with

ü Nanobots that can be turned off and on, and which would function as ‘experience beamers’ that allow us to experience the full range of other people’s sensory experiences too boring, we will have access to archives where more interesting experiences are stored. By 2030, non-biological thinking will be trillion of times more powerful than biological thinking.

ü Desktop molecular computers could have the computational power of a million human brains in terms of switching operations per second.

Humanity will be faced with a powerful, accelerated social revolution as a result of nanotechnology. In the near future a team of scientists will succeed in constructing the first nano-siezed robot capable of self replication. Within a few short years and five billion trillion nano-robots later, virtually all the present industrial processes will be obsolete, along with our contemporary concept of labour. Consumer goods will become plentiful, inexpensive, smart and durable. Medicine will take a quantum leap forward. Space travel and colonization will become safe and affordable. For these and other reasons, global lifestyles will change radically and human behaviour will be drastically impacted. The world is on the brink of a new technological revolution beyond any human experience. A new, more powerful industrial revolution capable of bringing wealth, health and education, without pollution, to every person on the planet is just around the corner. No longer need will forest to be cut or smoke spewed into the air. This is the promise of Nanotechnology.

REFERENCES:

o J.BR.Interplanet, Nanotechnology: Evolution of the concept

o The Future Impact Of Nanotechnology on textile technology and on textile industry

o IEEE Instrumentation & Measurement Magazine

o Electronics For You Magazine –June, 2002.