Document Sample
NANO TECHNOLOGY1 (DOC) Powered By Docstoc

Over the past few years, a little word with big potential has been rapidly insinuating itself into the worlds consciousness. That world is “nano”. It has conjured speculation about a seismic shift in almost every aspect of science and engineering within implication for ethics, economists, international relations, day to day life, and even humanity‟s conception of its place in the universe. Visionaries tour it as the panacea for all the woes. Nano research also crosses scientific disciplines. Chemists, biologists, doctors, physicists, engineers and computer scientists are intimately involved in nano development. Nano has fit the pages of such futurised publication as “wired magazine”, found it‟s way into science fiction and been the theme of episodes of star trek: the next generation and the x-files as well as a one linear in the movie spiderman. In the midst of all his buzz and activity, nano has moved from the world of the future to the world of the present. “Nano-scale science and engineering most likely will produce the strategic technology breakthroughs of tomorrow. Our ability to work at the molecular level, atom by atom to create something new, something we can manufacture from the „bottom up‟, open huge visits for many of us” says David Swain, senior VP of Engineering and Technology, boeing. Nano science and nanotechnology require us to imagine, make measure, use, and design on the nanoscale, because the nanoscale is so small, it is clearly difficult to do the imagine, the making, the measuring and using.

"In the future, nanotechnology will let us take off the boxing gloves" If we are to continue the revolution in computer hardware beyond about the next decade and will also let us fabricate an entire new generation of products that are cleaner, stronger, lighter and more precise. " Nanotechnology "has become very popular and is used to describe many type of research where the characteristics dimensions are less than about 1,000 namometers. For example, continued improvements in lithography have resulted in line widths that are less than one micron: this work is often called "nanotechnology". If we are to continue these trends we will have to develop a new manufacturing technology, which will let us inexpensively build computer systems with mole quantities of logic elements that are molecular in both size and precision and are interconnected in complex and highly idiosyncratic patterns. Nanotechnology will let us do this. Whatever we call it, it should let us   

Get essentially every atom in the right place. Make almost any structure consistent with the laws of physics that we can specify in molecular detail. Have manufacturing costs not greatly exceeding the cost of the required raw materials and energy.

There are two main concepts commonly associated with nanotechnology:  Positional assembly.  Massive parallelism.

The need for positional assembly implies an interest in molecular robotics, e.g., robotic devices that are molecular both in their size and precision. These molecular scale positional devices are likely to resemble very small versions of their everyday macroscopic counterparts. Positional assembly is frequently used in normal macroscopic manufacturing today, and provides tremendous advantages. The idea of manipulating and positioning individual atoms and molecules is still new and takes some getting used to.

One robotic arm assembling molecular parts is going to take a long time to assemble anything large- so we need lots of robotic arms: this is what we mean by massive parallelism. While earlier proposals achieved massive parallelism through self replication, today‟s “best guess” is that future molecular manufacturing systems will use some form of convergent assembly. In this process vast numbers of small parts we assembled by vast numbers of small robotic arms into larger parts, those larger parts, larger robotic arms assemble those larger parts, and so forth. If the size of the parts doubles at each iteration, we can go from one nanometers parts ( a few atoms in size) to one meter parts (almost as big as a person) in only 30 steps.

For the past 40 years, the electronic computers have grown more powerful as their transistor has been minimized. However the laws of quantum mechanics and the limitations of fabrication techniques soon will prevent further reduction in the minimum size of todays. Ongoing research uses the following that have shown that electronic nanodevices are possible   Mathematics Computer modeling

A Nanocomputer could be many orders of magnitude more powerful than today‟s microcomputers. The future Nanocomputer might be built upon experience with microcomputers, but take advantage of the very same quantum effects that limit current micro-scale transistors. The ultimate choice of technologies and designs will depend on the device speed, power dissipation reliability and ease of fabrication. It seems likely that along the development of molecular-scale manipulation tools, the first practical nanoelectronic circuits will emerge in this decade of the 21st century. The future Nanocomputer will largely transform our electronic computing and the technological infrastructure. It is amazing to see that the multidisciplinary nature of nanotechnology draws on so many talented scientists from different fields, from physics, chemistry, biology and computer science. It is difficult to predict from which traditional discipline will come the key breakthrough necessary to construct these future nanotechnological products.

Diamond Particles:
In biomaterials research, it has been found that even though a bulk material may be well-tolerated by the body, finely divided particles of the same material can often lead to severe and even carcinogenic complications in test animals. Differences in particle size influence histological reaction and cytokine production [22]. Many nanomedical applications will involve "particle" sized diamondoid objects (e.g., micronscale individual medical naorobots), so it is of great interest to review the experimental data relating to the reactions of specific cells to the presences of diamond particles. We already know that finely divided carbon particles are well-tolerated by the body -the passive nature of carbon in tissue has been known since ancient times, and both charcoal and lampblack (roughly spherical 10-20 nm particles) were used for ornamental and official tattoos.

In earlier people taught that the diamond particle that have been planned to pass in the human body will affect the human body will affect the human cells, the various experiments are done to overcome from this all fears. The given below cell are tested before giving the report.

(1) Neutrophils: (2) Monocytes and Macrophages (3) Fibroblasts (4) Other cells
And they also injected 3-micron diamond crystals in a10 mg/cm3 concentration (~0.3% Nct) injected into canine knee joints produced "little evidence of inflammation" - intra-articlular pressure remained low, along with the local cell count. A study by Dental.[35] observed no detectable hemolysis in vitro by various ceramic powders tested, including diamond, graphite and alumina, after 60 minutes cf exposure to a powder concentration of ~0.5 gm per cm3 of diluted blood (~14% Nct).

Great strength and lightweight are the exclusive province of diamond and graphic. Yet all share a common problem a common problem. We can‟t yet economically make them in the exact shapes that we want. Great strength is only one property that we prize highly. When we make computers we are more concerned by electrical properties. Here, too, diamond excels. Today‟s computers are made of semiconductors predominantly silicon. This is not because silicon is the ideal semiconductor from which to make computers, but because we know how to make devices from it. Diamond has a wider band gap, hence electrical devices will work at higher temperatures. It has greater thermal conductivity, so devices can be more easily cooled. It has greater breakdown field, hence devices can be smaller. It has higher speed. We can‟t economically manufacture them ye. Large pure crystals of silicon can be made relatively easily, but large pure crystals of diamond are scare.

To make the computer the pure crystals must also have an extremely precise and complex pattern of impurities. The exact location of the dopants atoms in the semiconductor lattice controls how device function and where signals can propagate. Logical order and long range complex order is crucial to make highly precise computer components crystals. It is the requirement for complex long-range order that prevents us from making computers of the kind we‟d like to make. While it‟s plausible we could make high-density memory from crystals and perhaps some types of cellular automatons, we couldn‟t make anything that resembled the computers on the market today. Today‟s high-speed semiconductor based digital computer has millions of logic elements wired together in complex and highly idiosyncratic patterns. This is well beyond the capabilities of crystal growth or biopolymer synthesis. It will require a fundamentally new manufacturing technology; molecular manufacturing or Nanotechnology.

Today, there is a gap in our synthetic abilities: we can make complex mechanical machinery and electronic devices (including computers, which have millions of transistors), but we can‟t make molecular computers and other macroscopic products as precise as molecules. Molecular manufacturing will let us economically manufacture almost any specified molecular structure that is stable.

Two fundamental mechanism in the growth process include:   Abstraction of hydrogen‟s from the diamond surface leaving behind reactive sites (dangling bonds, radicals). Interaction of carbon species (both reactive CH2, CH3, ETC.) as well as relatively unreactive species (C2H2) with the surface, thus depositing carbon. If we are to synthesize diamondoid structures it is plausible that we begin our search for the basic reaction steps involved in this synthesis by looking at exiting reactions that occur in the CVD growth of diamond. The use of the reactive gas in the synthesis process, however, the gas will interact with the growing surface at random.

POSITIONAL CONTROL: The ability to remove specific hydrogen atoms from the surface of the diamondoid work piece under construction is likely to be a fundamental unit operation in any attempt to make atomically precise diamondoid structures. It is unclear how to make this process site specific. In particular, the propynyl radical C3H3 has a great affinity for hydrogen, which offers great possibilities for positional control. Further, this radical have two ends: one end is highly reactive radical and second end is a stable sp3 carbon. Thus, we could synthesize a larger molecule with the propynyl radical at its end. The larger molecule would be held at the tip of a positional device.


Hydrogen Abstraction Tools

If we are to grow diamond, we must also have carbon deposition tools. Drexler has suggested the use of positionally controlled carbenes and alkynes and proposed reaction pathways and surface structure where these tools would apply [4].


FIG: A Positionally controlled carbene


FIG: A positionally controlled stained cycle alkine.
In both cases, the tools are positioned at a precise point on the growing diamondoid structure and are used to deposit one or more carbon at a desired location. These deposition reaction parallel proposals in the CVD literature except for the addition of positional control (e.g., at least one portion of the moiety must be part of an extended “handle” which can be held by a positional device.

The application of nanotechnology is pushing the barriers of diagnosis even further towards high-speed mass screening of samples for a multitude of diseases. In drug discovery, lab-on-a-chip technology is the basis for combinatorial screening y techniques, which, when combined with powerful computers (which also benefit from components with nanoscale features) can dramatically speed up the new drug discovery process. This enables many 'target' drugs to be quickly assessed and retained or discarded in a fraction of the time normally taken-and at a fraction of the cost.

The biological system is always looked by the nanotechnologists as the example of the future nanomachines. Prof. nadrian C.Seeman at New York University is the winner of the 1995 Feynman Prize in Nanotechnology. (The Nobel laureate Feynman died in 1988.The freynman Prize is sponsored by the Foresight Institute, and is given biennially for the scientific work that most advanced the development of molecular nanotechnology.). They also have used DNA to make four topological species - circle, trefoil knots of both signs and a figure-8 knot. They made the RNA knots as well and discovered the existence of a RNA topoisomerase. DNA-based topological control has also led to the construction of Borromean Rings, which could be used in DNA-based computing applications. In the DNA construction, the lack of a rigid molecule was a key feature. However recently they have used the antiparallel DNA double crossover molecules to incorporate in DNA assembles that make use of this rigidity to achieve control on the geometrical level as well as on the topological level.



Since most of the molecular drugs are nanosize, drug development is clearly a nanoscale activity. Because depression is cause by too low or too high a concentration of neurotransmitter molecules, intelligent nanoscale development of antidepressants is focused on increasing this concentration by blocking of decreasing the destruction of these molecules by modifying their binding properties. Since many proposed nanodrugs will work by well-understood and very specific mechanisms one of the major impacts of nanoscience and nanotechnology will be in facilitating development of entirely new drugs with fewer side effects and more beneficial behaviors.

In Photodynamic therapy, a particle is placed within the body and is illuminated with light from outside _light could come from laser or from a light bulb. The light is absorbed by the particle, after which several things may happen. If the particle is simply a metal Nanodot, the energy from the light will heat the dot and, therefore will heat any tissue within its neighborhood. With some particular molecular dots, light can also be used to produce highly energetic oxygen molecules.

Those oxygen molecules are very reactive and will chemically react with and Therefore destroy, most organic molecules that are next to them, including such nastier as Tumours. Photodynamic therapy does not leave a "toxic trail" of highly is based on Nanostructures ranging from simple's molecules through molecule/nanoparticle/ biological recognition agent composite structures. Clearly the design and optimization of such structures is matter of medical nanotechnology and holds promise as a noninvasive approach for dealing with many growths, tumors and disease.

Drug molecules should find places in the body where they will be effective. Antidepressants should be in the brain; anti-inflammatory at sites of stress and anticancer drugs at tumor sites. Bioavailability refers to presence of drug molecules where they are needed in body and where they will do most good. Nanotechnology and nanosciences are very useful in developing entirely new schemes for increasing Bioavailability and improving drug delivery. Molecules can be swallowed as part of the tablet and as the polymeric structures opens within the body, the enclosed drugs can be released. This is an effective method for creating time released drugs so that a pill taken once a day or once a week can continue to deliver the drug smoothly over an extended period of time.

Neuroelectronic interfaces involve the ideas of constructing nanodevices that will permit computers to be joined and linked to the nervous system. The construction of a Neuro-electronic interface simply requires the building of a molecular structure that will permit control and detection of nerve impulses by an external computer. The challenge is a combination of computational nanotechnology and bionanaotechnology. The nerves in the body convey messages by permitting electrical currents to flow between the brain and the nerve centers throughout the body. The most important ions for these signals are sodium and potassium ions, and they move along sheaths and channels that have evolved especially to permit facile, control label, rapid ionic motion. This is the mechanism that allows you to feel sensation such as putting your foot in hot water and feeling heat move from the local nerve through the nervous system into the brain where they are interpreted and processed. Often this process results in a response being filtered into the muscular system, as is demonstrated when you pupil your foot out of hot water. The aim of Neuroelectronic interface technology is to permit the registration, interpretation and response to these signals to be handles by a computer.

Biologists have any number of reasons to be interested in the movement of particular groups of cells and other structures as they move through the body or even sample in a dish. Tracking movement can help them to determine how well drugs are distributed and how substances are metabolized. But tracking a small group of cells as they move through the body is an essentially impossible task. In the past, scientists got around this problem by dyeing cells. If a sample of cells is green, and all other cells are more or less clear, its easy to spot the sample, organic dyes that have been used in the past can be toxic and must still be excited by light of certain frequency to cause them to fluoresce. Different color dyes absorb different frequencies of light. Consequently, if multiple samples are needed to be tracked at the

Same time, you may need as many lights sources as you have samples. This can become quite a problem. A. Paul Alivisatos, Moungi Bawendi, and their groups addressed with the introduction of luminescent tags. These tags are quantum tags often attached to proteins to allow them to penetrate cell walls. These quantum tags often attached to proteins to allow them to penetrate cell walls. These quantum dots exhibit the nanoscale property that their color is size dependent. They can be made out of bio inert materials and can be made of arbitrary size. This means that we select sizes where the frequency of light required to make another group of tags fluoresce; both can be lit with the same light source. At one stroke, these tags solve two major problems of the old organic dyes; toxicity and ability to use more that one color of tags at the same time with a single light source.

The long-term goal of nanotechnology is to built exactly what we want at low cost. Adding programmed positional control using small robotic manipulators to the existing methods used in synthesis should let us make a truly broad range of macroscopic products. Nanotechnology is not just present in fields that are traditionally high tech. Nano is now illiberally in fashion Advances in molecular scale composite materials have allowed companies like Nano- Tex to create next generation cloth and clothing.

1. Nanotechnology ---- A Gentle Introduction to the Next Big idea. Mark Ratner, Daniel Ratner. 2. 3. 4. 5. Www. Www. Www.

PRESENTED BY, JOFIA PRAKASH. J INDHUMATHY. C Pandian saraswathi yadav engineering college.

Shared By: