Nano Technology Edit

NANO TECHNOLOGY Introduction: Manufactured products are made from atoms. The properties of those products depend on how those atoms are arranged. If we rearrange the atoms in coal we can make diamond. If we rearrange the atoms in sand (and add a few other trace elements) we can make computer chips. If we rearrange the atoms in dirt, water and air we can make potatoes. Today’s manufacturing methods are very crude at the molecular level. Casting, grinding, milling and even lithography move atoms in great thundering statistical herds.But you can't really snap them together the way you'd like. In the future, through nanotechnology we'll be able to snap together the fundamental building blocks of nature easily, inexpensively and in most of the ways permitted by the laws of physics. This will be essential 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. The word "nanotechnology" has become very popular and is used to describe many types of research where the characteristic dimensions are less than about 1,000 nanometers. 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. Through Nanotechnology we can • • •

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 more concepts commonly associated with nanotechnology: • •

Positional assembly. Massive parallelism.

Clearly, we would be happy with any method that simultaneously achieved the first 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 massive parallelism (to keep the costs down). 1

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. 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. In this process vast numbers of small parts are assembled by vast numbers of small robotic arms into larger parts, those larger parts are assembled by larger robotic arms into still larger parts, and so forth. If the size of the parts doubles at each iteration, we can go from one nanometer parts (a few atoms in size) to one meter parts (almost as big as a person) in only 30 steps. Molecular Manufacturing OR Molecular Nanotechnology: Introduction: Manufactured products are made from atoms. The properties of those products depend on how those atoms are arranged. Viewed from the molecular level today's macroscopic manufacturing methods are crude and imprecise. Casting, milling, welding and all the other traditional manufacturing methods spray atoms about in great statistical herds. Even lithography (which already lets us put millions of transistors on a chip no bigger than your fingernail) is fundamentally statistical and random. Exactly how many dopant atoms are in a single transistor and exactly where each individual dopant atom is located is neither specified nor known: if we have roughly the right number in roughly the right place, we can make a working transistor. For today, that is good enough. The exception is chemistry. Large high purity crystals can have almost every atom in the right place. So, too, can many long polymers. The structures of proteins with hundreds and even thousands of amino acids can be specified down to the last atom. Most dramatically DNA strands with many tens of millions of bases can be copied with almost perfect accuracy. And it seems that almost any small molecule can be synthesized, if only we have the skill and patience. Yet the laws of physics and chemistry in principle permit arranging and rearranging the elements in so many combinations and permutations that all of our manufacturing skills and all of our chemical skills barely suffice to scratch the surface of what is possible.

2

The Utility of Diamond Almost any manufactured product could be improved, often by several orders of magnitude, if we could precisely control its structure at the molecular level. We often want our products to be light and strong. Diamond is light and strong: the strength-to-weight ratio of diamond is over 50 times that of steel. Yet we do not today have diamond spars in airplanes nor diamond hulls for rockets. Today we can't economically make diamond. Even if we could, simple diamond crystals can shatter. We'd have to modify the structure to make it tough and shatter proof: perhaps diamond fibers. While easily done in principle, we can't do this in practice today. 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, and the semiconductor of choice is 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. The computer industry has strong opinions about what makes a good logic device and what makes a good computer and diamond will let us make better computers than silicon Diamond has a wider bandgap, hence electrical devices will work at higher temperatures. It has greater thermal conductivity, so devices can be more easily cooled. It has a greater breakdown field, hence devices can be smaller. It has higher electron and hole mobility which, when combined with higher electric fields, will result in higher speed. But again, we see no diamond computers, just as we see no diamond airplanes: we can't economically manufacture them yet. Large pure crystals of silicon can be made relatively easily, but large pure crystals of diamond are scarce. We can etch the silicon surface and add dopants with a precision measured in tenths of microns, while the corresponding steps for diamond are more difficult. Not more difficult in principle: just more difficult today. Long Range Complex Order Making computers highlights another problem. It's not enough to make a pure crystal, it must also have an extremely precise and complex pattern of impurities. The exact location of the dopant atoms in the semiconductor lattice controls how devices function and where signals can propagate. Local order is crucial to make each device work, but long range complex order is crucial to make the computer as a whole work. While we can make some things today that are highly precise and have simple long range order (e.g., 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 semiconductorbased digital computers (like the 80486 or the Pentium) have millions of logic elements wired together in complex and highly idiosyncratic patterns. This is well beyond the

3

capabilities of crystal growth or bio-polymer synthesis. It will require a fundamentally new manufacturing technology: molecular manufacturing. The Interest of the Computer Industry The attraction of molecular manufacturing for the computer industry should be clear. It should let us make computers at a manufacturing cost of less than a dollar per pound, operating at frequencies of tens of gigahertz or more, with linear dimensions for a single device of roughly 10 nanometers, high reliability, and energy dissipation (using conventional methods) of roughly 10^-18 joules per logic operation. If we make thermodynamically reversible computers then the energy dissipation per logic operation can be reduced to well below kT at T = 300 Kelvins (well below 10^-21 joules). The computer industry is spending billions of dollars to make better computers. It is widely acknowledged within the industry that lithography is approaching its limits. There is already interest in molecular logic devices and that interest will increase sharply as improvements in conventional manufacturing methods become increasingly difficult. However, any new proposal for manufacturing molecular computers will be weighed against (at least) the criteria mentioned above. If it cannot easily beat conventional methods after they have been pushed to their uttermost limits, then it will be rejected. The computer industry will soon be pouring vast sums into research aimed at molecular computing, but the great bulk of funding will go towards well thought out proposals that offer a realistic possibility of substantially exceeding the performance of the ultimately evolved silicon VLSI technology that we expect to develop over the next decade. How We Make Diamond Today Today, we can synthesize diamond at low pressure and low temperature by using CVD (Chemical Vapor Deposition) methods. Diamond CVD growth involves highly reactive species (radicals, carbenes, etc.) in a gas over the growing diamond surface that bombard and react with that surface at random. Because reaction sites are random, growth of many defect structures occurs (dislocations, etc.) as well as the desired perfect diamond structure. Two fundamental mechanisms in the growth process include 1. Abstraction of hydrogen’s from the diamond surface leaving behind reactive sites. 2. Interaction of carbon species as well as relatively uncreative species with the

surface, thus depositing carbon. Conclusion The long term goal of molecular manufacturing is to build exactly what we want at low cost.

4

Convergent assembly

Introduction Nanotechnology can make big things as well as small things. An attractive approach is to use convergent assembly, which can rapidly make products whose size is measured in meters starting from building blocks whose size is measured in nanometers. It is based on the idea that smaller parts can be assembled into larger parts, larger parts can be assembled into still larger parts, and so forth. This process can be systematically repeated in a hierarchical fashion, creating an architecture able to span the size range from the molecular to the macroscopic. Convergent assembly covers a class of many different architectures.. The present proposal is simpler while retaining the desirable performance characteristics described in Nanosystems Convergent assembly It's common to make bigger things by assembling them from smaller things. A finished assembly which is about 1 meter in size might be made from eight smaller subassemblies each of about 0.5 meters in size. To make a 1 meter cube, we'd need to assemble eight smaller cubes, each of 0.5 meters in size. This relationship holds approximately for many products. We could assemble our eight subassemblies into a finished assembly by using one or more robotic arms (or other positional devices) in an assembly module (depicted abstractly in figure 1)..

5

Figure 1: a single assembly module able to accept subassemblies from the four input ports to the right, and which produces a finished assembly to the left through the single output port. If the output port has a size of one meter by one meter, each input port would have a size of 0.5 meters by 0.5 meters. This process could be repeated. We might take 64 sub-subassemblies, each with a size of about 0.25 meters, assemble them into 8 subassemblies, each with a size of about 0.5 meters, and finally assemble the 8 subassemblies into the finished assembly, with a size of about 1.0 meters. This could be done using the system shown in figure 2, which depicts a 1.0 meter assembly module connected to four 0.5 meter assembly modules.

Figure 2: two stages of assembly starting with 64 sub-subassemblies with a size of about 0.25 meters, producing 8 subassemblies with a size of about 0.5 meters, and producing a finished product with a size of about 1.0 meters. Let's assume that the final stage (which assembles the subassemblies into the final product) takes about 100 seconds.If the 1.0 meter assembly module takes 100 seconds, then the 0.5 meter assembly module should complete one subassembly in 50 seconds. This is because an object which is half the size can finish a movement of half the length in half the time: it's frequency of operation is doubled (see (Drexler,1992) for a discussion of scaling laws). Each 0.5 meter assembly module can therefore produce two subassemblies in 100 seconds. The four 0.5 meter assembly modules can finish eight subassemblies in 100

6

seconds, which means that both the 1.0 meter assembly module and the four 0.5 meter assembly modules must work for 100 seconds to produce the final product. This process can, of course, be continued. Figure 3 shows three stages of this process, in which 512 sub-sub-subassemblies are assembled in 16 0.25 meter assembly modules, making 64 sub-subassemblies; these 64 sub-subassemblies are assembled into 8 subassemblies in 4 0.5 meter assembly modules. Finally, the 8 subassemblies are assembled into the final product in the single 1.0 meter assembly module.

Figure 3: three stages of convergent assembly produce a final product of ~1.0 meters in size from 512 sub-sub-subassemblies each of which is ~0.125 meters in size. Again, the 0.25 meter assembly modules operate twice as fast as the 0.5 meter assembly modules, and four times as fast as the 1.0 meter assembly module. The 16 0.25 meter assembly modules can make 64 sub-subassemblies in the same time that the 4 0.5 meter assembly modules can make 8 subassemblies, which is the same amount of time that the single 1.0 meter assembly module takes to produce the finished product. We can keep adding stages to this process until the inputs to the first stage are as small as we might find convenient. For the purposes of molecular manufacturing, it is convenient to assume that these initial inputs are ~one nanometer in size.

7

Conclusions Convergent assembly is based on the idea that smaller parts can be successively assembled into ever larger parts. The particular architecture proposed should be able to produce meter-sized products in a few minutes from nanometer-sized parts while going through about 30 stages. At each stage the parts are approximately double the size of the parts from the previous stage and half the size of the parts in the succeeding stage.

Engines of Creation The Coming Era of Nanotechnology

ENGINES OF HEALING WE WILL USE molecular technology to bring health because the human body is made of molecules. The ill, the old, and the injured all suffer from mis-arranged patterns of atoms, whether mis-arranged by invading viruses or passing time. Devices able to rearrange atoms will be able to set them right. Nanotechnology will bring a fundamental breakthrough in medicine. From Drugs to Cell Repair Machines Being made of molecules, and having a human concern for our health, we will apply molecular machines to biomedical technology. Biologists already use antibodies to tag proteins, enzymes to cut and splice DNA, and viral syringes to inject edited DNA into bacteria. In the future, they will use assembler-built nanomachines to probe and modify cells. With tools like disassemblers, biologists will be able to study cell structures in ultimate, molecular detail. They then will catalog the hundreds of thousands of kinds of molecules in the body and map the structure of the hundreds of kinds of cells. Much as engineers might compile a parts list and make engineering drawings for an automobile, so biologists will describe the parts and structures of healthy tissue. By that time, they will be aided by sophisticated technical AI systems. Physicians aim to make tissues healthy, but with drugs and surgery they can only encourage tissues to repair themselves. Molecular machines will allow more direct repairs, bringing a new era in medicine.

8

To repair a car, a mechanic first reaches the faulty assembly, then identifies and removes the bad parts, and finally rebuilds or replaces them. Cell repair will involve the same basic tasks - tasks that living systems already prove possible. These tasks are Access. White blood cells leave the bloodstream and move through tissue, and viruses enter cells. Biologists even poke needles into cells without killing them. These examples show that molecular machines can reach and enter cells. Recognition. Antibodies and the tail fibers- and indeed, all specific biochemical interactions - show that molecular systems can recognize other molecules by touch. Disassembly. Digestive enzymes (and other, fiercer chemicals) show that molecular systems can disassemble damaged molecules. Rebuilding. Replicating cells show that molecular systems can build or rebuild every molecule found in a cell. Reassembly. Nature also shows that separated molecules can be put back together again.. Replicating cells show that molecular systems can assemble every system found in a cell. Thus, nature demonstrates all the basic operations that are needed to perform molecular-level repairs on cells.But systems based on nanomachines will generally be more compact and capable than those found in nature. Natural systems show us only lower bounds to the possible, in cell repair as in everything else. Cell Repair Machines In short, with molecular technology and technical AI we will compile complete, molecularlevel descriptions of healthy tissue, and we will build machines able to enter cells and to sense and modify their structures. Cell repair machines will be comparable in size to bacteria and viruses, but their more-compact parts will allow them to be more complex. They will travel through tissue as white blood cells do, and enter cells as viruses do - or they could open and close cell membranes with a surgeon's care. Inside a cell, a repair machine will first size up the situation by examining the cell's contents and activity, and then take action. Early cell repair machines will be highly specialized, able to recognize and correct only a single type of molecular disorder, such as an enzyme deficiency or a form of DNA damage. Later machines will be programmed with more general abilities. By working along molecule by molecule and structure by structure, repair machines will be able to repair whole cells. By working along cell by cell and tissue by tissue, they (aided by larger devices, where need be) will be able to repair whole organs. By working through a person organ by organ, they will restore health. Because molecular machines will be able to build molecules and cells from scratch, they will be able to repair even cells

9

damaged to the point of complete inactivity. Thus, cell repair machines will bring a fundamental breakthrough: they will free medicine from reliance on self-repair as the only path to healing. In practice, repair machines will compare DNA molecules from several cells, make corrected copies, and use these as standards for proofreading and repairing DNA throughout a tissue. By comparing several strands, repair machines will dramatically improve on nature's repair enzymes. Some Cures The simplest medical applications of nanomachines will involve not repair but selective destruction. Cancers provide one example; infectious diseases provide another. The goal is simple: one need only recognize and destroy the dangerous replicators, whether they are bacteria, cancer cells, viruses, or worms. Similarly, abnormal growths and deposits on arterial walls cause much heart disease; machines that recognize, break down, and dispose of them will clear arteries for more normal blood flow. Selective destruction will also cure diseases such as herpes in which a virus splices its genes into the DNA of a host cell. A repair device will enter the cell, read its DNA, and remove the addition that spells "herpes." Repairing damaged, cross-linked molecules will also be fairly straightforward. Faced with a damaged, cross-linked protein, a cell repair machine will first identify it by examining short amino acid sequences, then look up its correct structure in a data base. The machine will then compare the protein to this blueprint, one amino acid at a time. Like a proofreader finding misspellings and strange characters (char#cters), it will find any changed amino acids or improper cross-links. By correcting these flaws, it will leave a normal protein, ready to do the work of the cell.Repair machines will also aid healing. After a heart attack, scar tissue replaces dead muscle. Repair machines will stimulate the heart to grow fresh muscle by resetting cellular control mechanisms. By removing scar tissue and guiding fresh growth, they will direct the healing of the heart. Readers familiar with computers may prefer to think in terms of hardware and software. A machine could repair a computer's hardware while neither understanding nor changing its software From Function To Structure The reversibility of biostasis and irreversibility of severe stroke damage help to show how cell repair machines will change medicine. Today, physicians can only help tissues to heal themselves. Accordingly they must try to preserve the function of tissue. If tissues cannot function, they cannot heal. Cell repair machines change the central requirement from preserving function to preserving structure. As I noted in the discussion

10

of stroke, repair machines will be able to restore brain function with memory and skills intact only if the distinctive structure of the neural fabric remains intact. Biostasis involves preserving neural structure while deliberately blocking function. From Treating Disease To Establishing Health Medical researchers now study diseases, often seeking ways to prevent or reverse them by blocking a key step in the disease process. The resulting knowledge has helped physicians greatly: they now prescribe insulin to compensate for diabetes, antihypertensives to prevent stroke, penicillin to cure infections, and so on down an impressive list. Molecular machines will aid the study of diseases, yet they will make understanding disease far less important. Repair machines will make it more important to understand health. Once biologists have described normal molecules, cells, and tissues, properly programmed repair machines will be able to cure even unknown diseases. Once researchers describe the range of structures that a healthy liver may have, repair machines exploring a malfunctioning liver need only look for differences and correct them. Instead of fighting a million strange diseases, advanced repair machines will establish a state of health.

REFERENCES:- http: //www.googlesearch.com

11