Редактирование: Transhumanist FAQ Live (раздел)

===What is molecular nanotechnology?===

Molecular nanotechnology is an anticipated manufacturing technology that will make it possible to build complex three-dimensional structures to atomic specification using chemical reactions directed by nonbiological machinery. In molecular manufacturing, each atom would go to a selected place, bonding with other atoms in a precisely designated manner. Nanotechnology promises to give us thorough control of the structure of matter.

Since most of the stuff around us and inside us is composed of atoms and gets its characteristic properties from the placement of these atoms, the ability to control the structure of matter on the atomic scale has many applications. As K. Eric Drexler wrote in Engines of Creation, the first book on nanotechnology (published in 1986):

Coal and diamonds, sand and computer chips, cancer and healthy tissue: throughout history, variations in the arrangement of atoms have distinguished the cheap from the cherished, the diseased from the healthy. Arranged one way, atoms make up soil, air, and water arranged another, they make up ripe strawberries. Arranged one way, they make up homes and fresh air; arranged another, they make up ash and smoke.

Nanotechnology, by making it possible to rearrange atoms effectively, will enable us to transform coal into diamonds, sand into supercomputers, and to remove pollution from the air and tumors from healthy tissue.

Central to Drexler’s vision of nanotechnology is the concept of the assembler. An assembler would be a molecular construction device. It would have one or more submicroscopic robotic arms under computer control. The arms would be capable of holding and placing reactive compounds so as to positionally control the precise location at which a chemical reaction takes place. The assembler arms would grab a molecule (but not necessarily individual atoms) and add it to a work-piece, constructing an atomically precise object step by step. An advanced assembler would be able to make almost any chemically stable structure. In particular, it would be able to make a copy of itself. Since assemblers could replicate themselves, they would be easy to produce in large quantities.

There is a biological parallel to the assembler: the ribosome. Ribosomes are the tiny construction machines (a few thousand cubic nanometers big) in our cells that manufacture all the proteins used in all living things on Earth. They do this by assembling amino acids, one by one, into precisely determined sequences. These structures then fold up to form a protein. The blueprint that specifies the order of amino acids, and thus indirectly the final shape of the protein, is called messenger RNA. The messenger RNA is in turned determined by our DNA, which can be viewed (somewhat simplistically) as an instruction tape for protein synthesis. Nanotechnology will generalize the ability of ribosomes so that virtually any chemically stable structure can be built, including devices and materials that resemble nothing in nature.

Mature nanotechnology will transform manufacturing into a software problem. To build something, all you will need is a detailed design of the object you want to make and a sequence of instructions for its construction. Rare or expensive raw materials are generally unnecessary; the atoms required for the construction of most kinds of nanotech devices exist in abundance in nature. Dirt, for example, is full of useful atoms.

By working in large teams, assemblers and more specialized nanomachines will be able to build large objects quickly. Consequently, while nanomachines may have features on the scale of a billionth of a meter – a nanometer – the products could be as big as space vehicles or even, in a more distant future, the size of planets.

Because assemblers will be able to copy themselves, nanotech products will have low marginal production costs – perhaps on the same order as familiar commodities from nature’s own self-reproducing molecular machinery such as firewood, hay, or potatoes. By ensuring that each atom is properly placed, assemblers would manufacture products of high quality and reliability. Leftover molecules would be subject to this strict control, making the manufacturing process extremely clean.

The speed with which designs and instruction lists for making useful objects can be developed will determine the speed of progress after the creation of the first full-blown assembler. Powerful software for molecular modeling and design will accelerate development, possibly assisted by specialized engineering AI. Another accessory that might be especially useful in the early stages after the assembler-breakthrough is the disassembler, a device that can disassemble an object while creating a three-dimensional map of its molecular configuration. Working in concert with an assembler, it could function as a kind of 3D Xerox machine: a device for making atomically exact replicas of almost any existing solid object within reach.

Molecular nanotechnology will ultimately make it possible to construct compact computing systems performing at least 1021 operations per second; machine parts of any size made of nearly flawless diamond; cell-repair machines that can enter cells and repair most kinds of damage, in all likelihood including frostbite [see “ REF _Ref50109542 h What is cryonics? Isn’t the probability of success too small?”]; personal manufacturing and recycling appliances; and automated production systems that can double capital stock in a few hours or less. It is also likely to make uploading possible [see “What is uploading?”].

A key challenge in realizing these prospects is the bootstrap problem: how to build the first assembler. There are several promising routes. One is to improve current proximal probe technology. An atomic force microscope can drag individual atoms along a surface. Two physicists at IBM Almaden Labs in California illustrated this in 1989 when they used such a microscope to arrange 35 xenon atoms to spell out the trademark “I-B-M”, creating the world’s smallest logo. Future proximal probes might have more degrees of freedom and the ability to pick up and deposit reactive compounds in a controlled fashion.

Another route to the first assembler is synthetic chemistry. Cleverly designed chemical building blocks might be made to self-assemble in solution phase into machine parts. Final assembly of these parts might then be made with a proximal probe.

Yet another route is biochemistry. It might be possible to use ribosomes to make assemblers of more generic capabilities. Many biomolecules have properties that might be explored in the early phases of nanotechnology. For example, interesting structures, such as branches, loops, and cubes, have been made by DNA. DNA could also serve as a “tag” on other molecules, causing them to bind only to designated compounds displaying a complementary tag, thus providing a degree of control over what molecular complexes will form in a solution.

Combinations of these approaches are of course also possible. The fact that there are multiple promising routes adds to the likelihood that success will eventually be attained.

That assemblers of general capabilities are consistent with the laws of chemistry was shown by Drexler in his technical book Nanosystems in 1992. This book also established some lower bounds on the capabilities of mature nanotechnology. Medical applications of nanotechnology were first explored in detail by Robert A. Freitas Jr. in his monumental work Nanomedicine
, the first volume of which came out in 1999. Today, nanotech is a hot research field. The U.S. government spent more than 600 million dollars on its National Nanotechnology Initiative in 2002. Other countries have similar programs, and private investment is ample. However, only a small part of the funding goes to projects of direct relevance to the development of assembler-based nanotechnology; most of it is for more humdrum, near-term objectives.

While it seems fairly well established that molecular nanotechnology is in principle possible, it is harder to determine how long it will take to develop. A common guess among the cognoscenti is that the first assembler may be built around the year 2018, give or take a decade, but there is large scope for diverging opinion on the upper side of that estimate.

Because the ramifications of nanotechnology are immense, it is imperative that serious thought be given to this topic now. If nanotechnology were to be abused the consequences could be devastating. Society needs to prepare for the assembler breakthrough and do advance planning to minimize the risks associated with it [see e.g. “Aren’t these future technologies very risky? Could they even cause our extinction?”]. Several organizations are working to preparing the world for nanotechnology, the oldest and largest being the Foresight Institute.

References:

Drexler, E. The Engines of Creation: The Coming Era of Nanotechnology. (New York: Anchor Books, 1986). http://www.foresight.org/EOC/index.html

Drexler, E. Nanosystems: Molecular Machinery, Manufacturing, and Computation. (New York: John Wiley & Sons, Inc., 1992).

Freitas, Jr., R. A. Nanomedicine, Volume I: Basic Capabilities.
(Georgetown, Texas: Landes Bioscience, 1999).

Foresight Institute. http://www.foresight.org