Molecular nanotechnology
Encyclopedia
Molecular nanotechnology (MNT) is a technology based on the ability to build structures to complex, atomic specifications by means of mechanosynthesis
Mechanosynthesis
Mechanosynthesis is any chemical synthesis in which reaction outcomes are determined by the use of mechanical constraints to direct reactive molecules to specific molecular sites.-Introduction:...

. This is distinct from nanoscale materials
Nanomaterials
Nanomaterials is a field that takes a materials science-based approach to nanotechnology. It studies materials with morphological features on the nanoscale, and especially those that have special properties stemming from their nanoscale dimensions...

. Based on Richard Feynman
Richard Feynman
Richard Phillips Feynman was an American physicist known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics and the physics of the superfluidity of supercooled liquid helium, as well as in particle physics...

's vision of miniature factories using nanomachines to build complex products (including additional nanomachines
Self-replicating machine
A self-replicating machine is an artificial construct that is theoretically capable of autonomously manufacturing a copy of itself using raw materials taken from its environment, thus exhibiting self-replication in a way analogous to that found in nature. The concept of self-replicating machines...

), this advanced form of nanotechnology
Nanotechnology
Nanotechnology is the study of manipulating matter on an atomic and molecular scale. Generally, nanotechnology deals with developing materials, devices, or other structures possessing at least one dimension sized from 1 to 100 nanometres...

 (or molecular manufacturing) would make use of positionally-controlled mechanosynthesis
Mechanosynthesis
Mechanosynthesis is any chemical synthesis in which reaction outcomes are determined by the use of mechanical constraints to direct reactive molecules to specific molecular sites.-Introduction:...

 guided by molecular machine
Molecular machine
A molecular machine, or nanomachine, is any discrete number of molecular components that produce quasi-mechanical movements in response to specific stimuli . The expression is often more generally applied to molecules that simply mimic functions that occur at the macroscopic level...

 systems. MNT would involve combining physical principles demonstrated by chemistry, other nanotechnologies, and the molecular machinery of life with the systems engineering principles found in modern macroscale factories.

Introduction

While conventional chemistry uses inexact processes obtaining inexact results, and biology exploits inexact processes to obtain definitive results, molecular nanotechnology would employ original definitive processes to obtain definitive results. The desire in molecular nanotechnology would be to balance molecular reactions in positionally-controlled locations and orientations to obtain desired chemical reactions, and then to build systems by further assembling the products of these reactions.

A roadmap for the development of MNT is an objective of a broadly based technology project led by Battelle
Battelle Memorial Institute
Battelle Memorial Institute is a private nonprofit applied science and technology development company headquartered in Columbus, Ohio. Battelle is a charitable trust organized as a nonprofit corporation under the laws of the State of Ohio and is exempt from taxation under Section 501 of the...

 (the manager of several U.S. National Laboratories) and the Foresight Institute
Foresight Institute
The Foresight Institute is a Palo Alto, California-based nonprofit organization for promoting transformative technologies. They sponsor conferences on molecular nanotechnology, publish reports, and produce a newsletter....

. The roadmap was originally scheduled for completion by late 2006, but was released in January 2008. The Nanofactory Collaboration is a more focused ongoing effort involving 23 researchers from 10 organizations and 4 countries that is developing a practical research agenda specifically aimed at positionally-controlled diamond mechanosynthesis and diamondoid nanofactory development. In August 2005, a task force consisting of 50+ international experts from various fields was organized by the Center for Responsible Nanotechnology
Center for Responsible Nanotechnology
Center for Responsible Nanotechnology is a non-profit research and advocacy organization with a focus on molecular manufacturing and its possible effects, both positive and negative...

 to study the societal implications of molecular nanotechnology.

Smart materials and nanosensors

One proposed application of MNT is so-called smart material
Smart material
Smart materials or designed materials are materials that have one or more properties that can be significantly changed in a controlled fashion by external stimuli, such as stress, temperature, moisture, pH, electric or magnetic fields....

s. This term refers to any sort of material designed and engineered at the nanometer scale for a specific task. It encompasses a wide variety of possible commercial applications. One example would be materials designed to respond differently to various molecules; such a capability could lead, for example, to artificial drugs which would recognize and render inert specific viruses. Another is the idea of self-healing structures, which would repair small tears in a surface naturally in the same way as self-sealing tires or human skin.

A MNT nanosensor would resemble a smart material, involving a small component within a larger machine that would react to its environment and change in some fundamental, intentional way. A very simple example: a photosensor might passively measure the incident light and discharge its absorbed energy as electricity when the light passes above or below a specified threshold, sending a signal to a larger machine. Such a sensor would supposedly cost less and use less power than a conventional sensor, and yet function usefully in all the same applications — for example, turning on parking lot lights when it gets dark.

While smart materials and nanosensors both exemplify useful applications of MNT, they pale in comparison with the complexity of the technology most popularly associated with the term: the replicating nanorobot.

Replicating nanorobots

MNT nanofacturing is popularly linked with the idea of swarm
Swarm intelligence
Swarm intelligence is the collective behaviour of decentralized, self-organized systems, natural or artificial. The concept is employed in work on artificial intelligence...

s of coordinated nanoscale robots working together, a popularization of an early proposal by Drexler in his 1986 discussions of MNT
Engines of Creation
Engines of Creation: The Coming Era of Nanotechnology is a 1986 molecular nanotechnology book written by K. Eric Drexler with a foreword by Marvin Minsky. An updated version was released in 2007...

, but superseded in 1992. In this early proposal, sufficiently capable nanorobots would construct more nanorobots in an artificial environment containing special molecular building blocks.

Critics have doubted both the feasibility of self-replicating nanorobots and the feasibility of control if self-replicating nanorobots could be achieved: they cite the possibility of mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...

s removing any control and favoring reproduction of mutant pathogenic variations. Advocates address the first doubt by pointing out that the first macroscale autonomous machine replicator, made of Lego blocks, was built and operated experimentally in 2002. While there are sensory advantages present at the macroscale compared to the limited sensorium available at the nanoscale, proposals for positionally controlled nanoscale mechanosynthetic fabrication systems employ dead reckoning of tooltips combined with reliable reaction sequence design to ensure reliable results, hence a limited sensorium is no handicap; similar considerations apply to the positional assembly of small nanoparts. Advocates address the second doubt by arguing that bacteria are (of necessity) evolved to evolve, while nanorobot mutation could be actively prevented by common error-correcting techniques. Similar ideas are advocated in the Foresight Guidelines on Molecular Nanotechnology, and a map of the 137-dimensional replicator design space recently published by Freitas and Merkle provides numerous proposed methods by which replicators could, in principle, be safely controlled by good design.

However, the concept of suppressing mutation raises the question: How can design evolution occur at the nanoscale without a process of random mutation and deterministic selection? Critics argue that MNT advocates have not provided a substitute for such a process of evolution in this nanoscale arena where conventional sensory-based selection processes are lacking. The limits of the sensorium available at the nanoscale could make it difficult or impossible to winnow successes from failures. Advocates argue that design evolution should occur deterministically and strictly under human control, using the conventional engineering paradigm of modeling, design, prototyping, testing, analysis, and redesign.

In any event, since 1992 technical proposals for MNT do not include self-replicating nanorobots, and recent ethical guidelines put forth by MNT advocates prohibit unconstrained self-replication.

Medical nanorobots

One of the most important applications of MNT would be medical nanorobotics
Nanorobotics
Nanorobotics is the emerging technology field of creating machines or robots whose components are at or close to the scale of a nanometer . More specifically, nanorobotics refers to the nanotechnology engineering discipline of designing and building nanorobots, with devices ranging in size from...

 or nanomedicine
Nanomedicine
Nanomedicine is the medical application of nanotechnology. Nanomedicine ranges from the medical applications of nanomaterials, to nanoelectronic biosensors, and even possible future applications of molecular nanotechnology. Current problems for nanomedicine involve understanding the issues related...

, an area pioneered by Robert Freitas
Robert Freitas
Robert A. Freitas Jr. is a Senior Research Fellow, one of four researchers at the nonprofit foundation Institute for Molecular Manufacturing in Palo Alto, California. He holds a 1974 Bachelor's degree majoring in both physics and psychology from Harvey Mudd College, and a 1978 Juris Doctor degree...

 in numerous books and papers. The ability to design, build, and deploy large numbers of medical nanorobots would, at a minimum, make possible the rapid elimination of disease and the reliable and relatively painless recovery from physical trauma. Medical nanorobots might also make possible the convenient correction of genetic defects, and help to ensure a greatly expanded healthspan. More controversially, medical nanorobots might be used to augment natural human capabilities. However, mechanical medical nanodevices would not be allowed (or designed) to self-replicate inside the human body, nor would medical nanorobots have any need for self-replication themselves since they would be manufactured exclusively in carefully regulated nanofactories.

Utility fog

Another proposed application of molecular nanotechnology is "utility fog
Utility fog
Utility fog is a hypothetical collection of tiny robots that can replicate a physical structure. As such, it is a form of self-reconfiguring modular robotics.-Conception:...

" — in which a cloud of networked microscopic robots (simpler than assembler
Molecular assembler
A molecular assembler, as defined by K. Eric Drexler, is a "proposed device able to guide chemical reactions by positioning reactive molecules with atomic precision". Some biological molecules such as ribosomes fit this definition. This is because they receive instructions from messenger RNA and...

s) would change its shape and properties to form macroscopic objects and tools in accordance with software commands. Rather than modify the current practices of consuming material goods in different forms, utility fog would simply replace many physical objects.

Phased-array optics

Yet another proposed application of MNT would be phased-array optics (PAO). However, this appears to be a problem addressable by ordinary nanoscale technology. PAO would use the principle of phased-array millimeter technology but at optical wavelengths. This would permit the duplication of any sort of optical effect but virtually. Users could request holograms, sunrises and sunsets, or floating lasers as the mood strikes. PAO systems were described in BC Crandall's Nanotechnology: Molecular Speculations on Global Abundance in the Brian Wowk
Brian Wowk
Brian G. Wowk, Ph.D. is a medical physicist and cryobiologist known for the discovery and development of syntheticmolecules that mimic the activity of natural antifreeze proteins in cryopreservation applications, sometimes called "ice blockers"...

 article "Phased-Array Optics."

Benefits


Nanotechnology (or molecular nanotechnology to refer more specifically to the goals discussed here) will let us continue the historical trends in manufacturing right up to the fundamental limits imposed by physical law. It will let us make remarkably powerful molecular computers. It will let us make materials over fifty times lighter than steel or aluminium alloy but with the same strength. We'll be able to make jets, rockets, cars or even chairs that, by today's standards, would be remarkably light, strong, and inexpensive. Molecular surgical tools, guided by molecular computers and injected into the blood stream could find and destroy cancer cells or invading bacteria, unclog arteries, or provide oxygen when the circulation is impaired.



Nanotechnology will replace our entire manufacturing base with a new, radically more precise, radically less expensive, and radically more flexible way of making products. The aim is not simply to replace today's computer chip making plants, but also to replace the assembly lines for cars, televisions, telephones, books, surgical tools, missiles, bookcases, airplanes, tractors, and all the rest. The objective is a pervasive change in manufacturing, a change that will leave virtually no product untouched. Economic progress and military readiness in the 21st Century will depend fundamentally on maintaining a competitive position in nanotechnology.


Despite the current early developmental status of nanotechnology and molecular nanotechnology, much concern surrounds MNT's anticipated impact on economics
Economics
Economics is the social science that analyzes the production, distribution, and consumption of goods and services. The term economics comes from the Ancient Greek from + , hence "rules of the house"...

 and on law
Law
Law is a system of rules and guidelines which are enforced through social institutions to govern behavior, wherever possible. It shapes politics, economics and society in numerous ways and serves as a social mediator of relations between people. Contract law regulates everything from buying a bus...

. Whatever the exact effects, MNT, if achieved, would tend to reduce the scarcity
Scarcity
Scarcity is the fundamental economic problem of having humans who have unlimited wants and needs in a world of limited resources. It states that society has insufficient productive resources to fulfill all human wants and needs. Alternatively, scarcity implies that not all of society's goals can be...

 of manufactured goods and make many more goods (such as food and health aids) manufacturable.

It is generally considered that future citizens of a molecular-nanotechnological society would still need money, in the form of unforgeable digital cash or physical specie (in special circumstances). They might use such money to buy goods and services that are unique, or limited within the solar system. These might include: matter, energy, information, real estate, design services, entertainment services, legal services, fame, political power, or the attention of other people to ones political/religious/philosophical message. Furthermore, futurists must consider war, even between prosperous states, and non-economic goals.

If MNT were realized, some resources would remain limited, because unique physical objects are limited (a plot of land in the real Jerusalem, mining rights to the larger near-earth asteroids) or because they depend on the goodwill of a particular person (the love of a famous person, a live audience in a musical concert). Demand will always exceed supply for some things, and a political economy
Political economy
Political economy originally was the term for studying production, buying, and selling, and their relations with law, custom, and government, as well as with the distribution of national income and wealth, including through the budget process. Political economy originated in moral philosophy...

 may continue to exist in any case. Whether the interest in these limited resources would diminish with the advent of virtual reality
Virtual reality
Virtual reality , also known as virtuality, is a term that applies to computer-simulated environments that can simulate physical presence in places in the real world, as well as in imaginary worlds...

, where they could be easily substituted, is yet unclear. One reason why it might not is a hypothetical preference for "the real thing", although such an opinion could easily be mollified if virtual reality were to develop to a certain level of quality.

MNT should make possible nanomedical capabilities able to cure any medical condition not already cured by advances in other areas. Good health would be common, and poor health of any form would be as rare as smallpox and scurvy are today. Even cryonics
Cryonics
Cryonics is the low-temperature preservation of humans and animals who can no longer be sustained by contemporary medicine, with the hope that healing and resuscitation may be possible in the future. Cryopreservation of people or large animals is not reversible with current technology...

 would be feasible, as cryopreserved tissue could be fully repaired.

Risks

Molecular nanotechnology is one of the technologies that some analysts believe could lead to a Technological Singularity
Technological singularity
Technological singularity refers to the hypothetical future emergence of greater-than-human intelligence through technological means. Since the capabilities of such an intelligence would be difficult for an unaided human mind to comprehend, the occurrence of a technological singularity is seen as...

.
Some feel that molecular nanotechnology would have daunting risks. It conceivably could enable cheaper and more destructive conventional weapon
Weapon
A weapon, arm, or armament is a tool or instrument used with the aim of causing damage or harm to living beings or artificial structures or systems...

s. Also, molecular nanotechnology might permit weapons of mass destruction
Weapons of mass destruction
A weapon of mass destruction is a weapon that can kill and bring significant harm to a large number of humans and/or cause great damage to man-made structures , natural structures , or the biosphere in general...

 that could self-replicate, as viruses and cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

 cells do when attacking the human body. Commentators generally agree that, in the event molecular nanotechnology were developed, mankind should permit self-replication
Self-replication
Self-replication is any behavior of a dynamical system that yields construction of an identical copy of that dynamical system. Biological cells, given suitable environments, reproduce by cell division. During cell division, DNA is replicated and can be transmitted to offspring during reproduction...

 only under very controlled or "inherently safe" conditions.

A fear exists that nanomechanical robots, if achieved, and if designed to self-replicate using naturally occurring materials (a difficult task), could consume the entire planet in their hunger for raw materials, or simply crowd out natural life, out-competing it for energy (as happened historically when blue-green algae appeared and outcompeted earlier life forms). Some commentators have referred to this situation as the "grey goo
Grey goo
Grey goo is a hypothetical end-of-the-world scenario involving molecular nanotechnology in which out-of-control self-replicating robots consume all matter on Earth while building more of themselves, a scenario known as ecophagy .Self-replicating machines of the macroscopic variety were originally...

" or "ecophagy
Ecophagy
Ecophagy is a term coined by Robert Freitas that means the literal consuming of an ecosystem. It derives from the Greek "οικος" or Late Latin "oeco-", which refers to a "house" or "household", and Greek φᾰγεῖν phagein "to eat"...

" scenario. K. Eric Drexler
K. Eric Drexler
Dr. Kim Eric Drexler is an American engineer best known for popularizing the potential of molecular nanotechnology , from the 1970s and 1980s.His 1991 doctoral thesis at MIT was revised and published as...

 considers an accidental "grey goo
Grey goo
Grey goo is a hypothetical end-of-the-world scenario involving molecular nanotechnology in which out-of-control self-replicating robots consume all matter on Earth while building more of themselves, a scenario known as ecophagy .Self-replicating machines of the macroscopic variety were originally...

" scenario extremely unlikely and says so in later editions of Engines of Creation.

In light of this perception of potential danger, the Foresight Institute
Foresight Institute
The Foresight Institute is a Palo Alto, California-based nonprofit organization for promoting transformative technologies. They sponsor conferences on molecular nanotechnology, publish reports, and produce a newsletter....

 (founded by K. Eric Drexler
K. Eric Drexler
Dr. Kim Eric Drexler is an American engineer best known for popularizing the potential of molecular nanotechnology , from the 1970s and 1980s.His 1991 doctoral thesis at MIT was revised and published as...

 to prepare for the arrival of future technologies) has drafted a set of guidelines for the ethical development of nanotechnology. These include the banning of free-foraging self-replicating pseudo-organisms on the Earth's surface, at least, and possibly in other places.

Technical issues and criticism

The feasibility of the basic technologies analyzed in Nanosystems has been the subject of a formal scientific review by U.S. National Academy of Sciences, and has also been the focus of extensive debate on the internet and in the popular press.

Study and recommendations by the U.S. National Academy of Sciences

In 2006, U.S. National Academy of Sciences released the report of a study of molecular manufacturing as part of a longer report, A Matter of Size: Triennial Review of the National Nanotechnology Initiative The study committee reviewed the technical content of Nanosystems, and in its conclusion states that no current theoretical analysis can be considered definitive regarding several questions of potential system performance, and that optimal paths for implementing high-performance systems cannot be predicted with confidence. It recommends experimental research to advance knowledge in this area:
"Although theoretical calculations can be made today, the eventually attainable range of chemical reaction cycles, error rates, speed of operation, and thermodynamic efficiencies of such bottom-up manufacturing systems cannot be reliably predicted at this time. Thus, the eventually attainable perfection and complexity of manufactured products, while they can be calculated in theory, cannot be predicted with confidence. Finally, the optimum research paths that might lead to systems which greatly exceed the thermodynamic efficiencies and other capabilities of biological systems cannot be reliably predicted at this time. Research funding that is based on the ability of investigators to produce experimental demonstrations that link to abstract models and guide long-term vision is most appropriate to achieve this goal."

Assemblers versus nanofactories

A section heading in Drexler's Engines of Creation
Engines of Creation
Engines of Creation: The Coming Era of Nanotechnology is a 1986 molecular nanotechnology book written by K. Eric Drexler with a foreword by Marvin Minsky. An updated version was released in 2007...

reads "Universal Assemblers", and the following text speaks of assembler
Assembler
Assembler may refer to:* Assembler , for an assembly language, a computer program to translate between lower-level representations of computer programs...

s which could hypothetically "build almost anything that the laws of nature allow to exist." Drexler's colleague Ralph Merkle
Ralph Merkle
Ralph C. Merkle is a researcher in public key cryptography, and more recently a researcher and speaker on molecular nanotechnology and cryonics...

 has noted that, contrary to widespread legend, Drexler never claimed that assembler systems could build absolutely any molecular structure. The endnotes in Drexler's book explain the qualification "almost": "For example, a delicate structure might be designed that, like a stone arch, would self-destruct unless all its pieces were already in place. If there were no room in the design for the placement and removal of a scaffolding, then the structure might be impossible to build. Few structures of practical interest seem likely to exhibit such a problem, however."

In 1992, Drexler published Nanosystems: Molecular Machinery, Manufacturing, and Computation, a detailed proposal for synthesizing stiff covalent structures using a table-top factory. Diamondoid
Diamondoid
A diamondoid, in the context of building materials for nanotechnology components, most generally refers to structures that resemble diamond in a broad sense: namely, strong, stiff structures containing dense, 3-D networks of covalent bonds, formed chiefly from first and second row atoms with a...

 structures and other stiff covalent structures, if achieved, would have a wide range of possible applications, going far beyond current MEMS
Microelectromechanical systems
Microelectromechanical systems is the technology of very small mechanical devices driven by electricity; it merges at the nano-scale into nanoelectromechanical systems and nanotechnology...

 technology. An outline of a path was put forward in 1992 for building a table-top factory in the absence of an assembler. Other researchers have begun advancing tentative, alternative proposed paths for this in the years since Nanosystems was published.

Hard versus soft nanotechnology

In 2004 Richard Jones wrote Soft Machines (nanotechnology and life), a book for lay audiences published by Oxford University. In this book he describes radical nanotechnology as a deterministic/mechanistic idea of nano engineered machines that does not take into account the nanoscale challenges such as wetness, stickness, brownian motion, high viscosity (Drexler view). He also explains what is soft nanotechnology or more appropriatelly biomimetic nanotechnology which is the way forward, if not the best way, to design functional nanodevices that can cope with all the problems at a nanoscale. One can think of soft nanotechnology as the development of nanomachines that uses the lessons learned from biology on how things work, chemistry to precisely engineer such devices and stochastic physics to model the system and its natural processes in detail.

The Smalley-Drexler debate

Several researchers, including Nobel Prize winner Dr. Richard Smalley
Richard Smalley
Richard Errett Smalley was the Gene and Norman Hackerman Professor of Chemistry and a Professor of Physics and Astronomy at Rice University, in Houston, Texas...

 (1943–2005), attacked the notion of universal assemblers, leading to a rebuttal from Drexler and colleagues, and eventually to an exchange of letters. Smalley argued that chemistry is extremely complicated, reactions are hard to control, and that a universal assembler is science fiction. Drexler and colleagues, however, noted that Drexler never proposed universal assemblers able to make absolutely anything, but instead proposed more limited assemblers able to make a very wide variety of things. They challenged the relevance of Smalley's arguments to the more specific proposals advanced in Nanosystems. Also, Smalley argued that nearly all of modern chemistry involves reactions that take place in a solvent (usually water), because the small molecules of a solvent contribute many things, such as lowering binding energies for transition states. Since nearly all known chemistry requires a solvent, Smalley felt that Drexler's proposal to use a high vacuum environment was not feasible. However, Drexler addresses this in Nanosystems by showing mathematically that well designed catalysts can provide the effects of a solvent and can fundamentally be made even more efficient than a solvent/enzyme reaction could ever be.

Design issues

For the future, some means has to be found for MNT design evolution at the nanoscale which mimics the process of biological evolution at the molecular scale. Biological evolution proceeds by random variation in ensemble averages of organisms combined with culling of the less-successful variants and reproduction of the more-successful variants, and macroscale engineering design also proceeds by a process of design evolution from simplicity to complexity as set forth somewhat satirically by John Gall: "A complex system that works is invariably found to have evolved from a simple system that worked. . . . A complex system designed from scratch never works and can not be patched up to make it work. You have to start over, beginning with a system that works." A breakthrough in MNT is needed which proceeds from the simple atomic ensembles which can be built with, e.g., an STM to complex MNT systems via a process of design evolution. A handicap in this process is the difficulty of seeing and manipulation at the nanoscale compared to the macroscale which makes deterministic selection of successful trials difficult; in contrast biological evolution proceeds via action of what Richard Dawkins has called the "blind watchmaker"

comprising random molecular variation and deterministic reproduction/extinction.

At present in 2007 the practice of nanotechnology embraces both stochastic approaches (in which, for example, supramolecular chemistry
Supramolecular chemistry
Supramolecular chemistry refers to the area of chemistry beyond the molecules and focuses on the chemical systems made up of a discrete number of assembled molecular subunits or components...

 creates waterproof pants) and deterministic approaches wherein single molecules (created by stochastic chemistry) are manipulated on substrate surfaces (created by stochastic deposition methods) by deterministic methods comprising nudging them with STM
Scanning tunneling microscope
A scanning tunneling microscope is an instrument for imaging surfaces at the atomic level. Its development in 1981 earned its inventors, Gerd Binnig and Heinrich Rohrer , the Nobel Prize in Physics in 1986. For an STM, good resolution is considered to be 0.1 nm lateral resolution and...

 or AFM
Atomic force microscope
Atomic force microscopy or scanning force microscopy is a very high-resolution type of scanning probe microscopy, with demonstrated resolution on the order of fractions of a nanometer, more than 1000 times better than the optical diffraction limit...

 probes and causing simple binding or cleavage reactions to occur. The dream of a complex, deterministic molecular nanotechnology remains elusive. Since the mid 1990s, thousands of surface scientists and thin film technocrats have latched on to the nanotechnology bandwagon and redefined their disciplines as nanotechnology. This has caused much confusion in the field and has spawned thousands of "nano"-papers on the peer reviewed literature. Most of these reports are extensions of the more ordinary research done in the parent fields.

The feasibility of the proposals in Nanosystems

The feasibility of Drexler's proposals largely depends, therefore, on whether designs like those in Nanosystems could be built in the absence of a universal assembler to build them and would work as described. Supporters of molecular nanotechnology frequently claim that no significant errors have been discovered in Nanosystems since 1992. Even some critics concede that "Drexler has carefully considered a number of physical principles underlying the 'high level' aspects of the nanosystems he proposes and, indeed, has thought in some detail" about some issues.

Other critics claim, however, that Nanosystems omits important chemical details about the low-level 'machine language' of molecular nanotechnology. They also claim that much of the other low-level chemistry in Nanosystems requires extensive further work, and that Drexler's higher-level designs therefore rest on speculative foundations. Recent such further work by Freitas and Merkle is aimed at strengthening these foundations by filling the existing gaps in the low-level chemistry.

Drexler argues that we may need to wait until our conventional nanotechnology
Nanotechnology
Nanotechnology is the study of manipulating matter on an atomic and molecular scale. Generally, nanotechnology deals with developing materials, devices, or other structures possessing at least one dimension sized from 1 to 100 nanometres...

 improves before solving these issues: "Molecular manufacturing will result from a series of advances in molecular machine systems, much as the first Moon landing resulted from a series of advances in liquid-fuel rocket
Rocket
A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...

 systems. We are now in a position like that of the British Interplanetary Society
British Interplanetary Society
The British Interplanetary Society founded in 1933 by Philip E. Cleator, is the oldest space advocacy organisation in the world whose aim is exclusively to support and promote astronautics and space exploration.-Structure:...

 of the 1930s which described how multistage liquid-fueled rockets could reach the Moon and pointed to early rockets as illustrations of the basic principle." However, Freitas and Merkle argue that a focused effort to achieve diamond mechanosynthesis (DMS) can begin now, using existing technology, and might achieve success in less than a decade if their "direct-to-DMS approach is pursued rather than a more circuitous development approach that seeks to implement less efficacious nondiamondoid molecular manufacturing technologies before progressing to diamondoid".

To summarize the arguments against feasibility: First, critics argue that a primary barrier to achieving molecular nanotechnology is the lack of an efficient way to create machines on a molecular/atomic scale, especially in the absence of a well-defined path toward a self-replicating assembler or diamondoid nanofactory. Advocates respond that a preliminary research path leading to a diamondoid nanofactory is being developed.

A second difficulty in reaching molecular nanotechnology is design. Hand design of a gear or bearing at the level of atoms might take a few to several weeks. While Drexler, Merkle and others have created designs of simple parts, no comprehensive design effort for anything approaching the complexity of a Model T Ford has been attempted. Advocates respond that it is difficult to undertake a comprehensive design effort in the absence of significant funding for such efforts, and that despite this handicap much useful design-ahead has nevertheless been accomplished with new software tools that have been developed, e.g., at Nanorex.

In the latest report A Matter of Size: Triennial Review of the National Nanotechnology Initiative put out by the National Academies Press in December 2006 (roughly twenty years after Engines of Creation was published), no clear way forward toward molecular nanotechnology could yet be seen, as per the conclusion on page 108 of that report: "Although theoretical calculations can be made today, the eventually attainable
range of chemical reaction cycles, error rates, speed of operation, and thermodynamic
efficiencies of such bottom-up manufacturing systems cannot be reliably
predicted at this time. Thus, the eventually attainable perfection and complexity of
manufactured products, while they can be calculated in theory, cannot be predicted
with confidence. Finally, the optimum research paths that might lead to systems
which greatly exceed the thermodynamic efficiencies and other capabilities of
biological systems cannot be reliably predicted at this time. Research funding that
is based on the ability of investigators to produce experimental demonstrations
that link to abstract models and guide long-term vision is most appropriate to
achieve this goal." This call for research leading to demonstrations is welcomed by groups such as the Nanofactory Collaboration who are specifically seeking experimental successes in diamond mechanosynthesis. The "Technology Roadmap for Productive Nanosystems
Productive nanosystems
The defines "productive nanosystems" as functional nanometer-scale systems that make atomically-specified structures and devices under programmatic control, i.e. they perform manufacturing to atomic precision....

" aims to offer additional constructive insights.

It is perhaps interesting to ask whether or not most structures consistent with physical law can in fact be manufactured. Advocates assert that to achieve most of the vision of molecular manufacturing it is not necessary to be able to build "any structure that is compatible with natural law." Rather, it is necessary to be able to build only a sufficient (possibly modest) subset of such structures—as is true, in fact, of any practical manufacturing process used in the world today, and is true even in biology. In any event, as Richard Feynman
Richard Feynman
Richard Phillips Feynman was an American physicist known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics and the physics of the superfluidity of supercooled liquid helium, as well as in particle physics...

 once said, "It is scientific only to say what's more likely or less likely, and not to be proving all the time what's possible or impossible."

Existing work on diamond mechanosynthesis

There is a growing body of peer-reviewed theoretical work on synthesizing diamond by mechanically removing/adding hydrogen atoms and depositing carbon atoms (a process known as mechanosynthesis
Mechanosynthesis
Mechanosynthesis is any chemical synthesis in which reaction outcomes are determined by the use of mechanical constraints to direct reactive molecules to specific molecular sites.-Introduction:...

). This work is slowly permeating the broader nanoscience community and is being critiqued. For instance, Peng et al. (2006) (in the continuing research effort by Freitas, Merkle and their collaborators) reports that the most-studied mechanosynthesis tooltip motif (DCB6Ge) successfully places a C2 carbon dimer on a C(110) diamond
Diamond
In mineralogy, diamond is an allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at ambient conditions...

 surface at both 300 K (room temperature) and 80 K (liquid nitrogen
Liquid nitrogen
Liquid nitrogen is nitrogen in a liquid state at a very low temperature. It is produced industrially by fractional distillation of liquid air. Liquid nitrogen is a colourless clear liquid with density of 0.807 g/mL at its boiling point and a dielectric constant of 1.4...

 temperature), and that the silicon variant (DCB6Si) also works at 80 K but not at 300 K. Over 100,000 CPU hours were invested in this latest study. The DCB6 tooltip motif, initially described by Merkle and Freitas at a Foresight Conference in 2002, was the first complete tooltip ever proposed for diamond mechanosynthesis and remains the only tooltip motif that has been successfully simulated for its intended function on a full 200-atom diamond surface.

The tooltips modeled in this work are intended to be used only in carefully controlled environments (e.g., vacuum). Maximum acceptable limits for tooltip translational and rotational misplacement errors are reported in Peng et al. (2006) -- tooltips must be positioned with great accuracy to avoid bonding the dimer incorrectly. Peng et al. (2006) reports that increasing the handle thickness from 4 support planes of C atoms above the tooltip to 5 planes decreases the resonance frequency of the entire structure from 2.0 THz to 1.8 THz. More importantly, the vibrational footprints of a DCB6Ge tooltip mounted on a 384-atom handle and of the same tooltip mounted on a similarly constrained but much larger 636-atom "crossbar" handle are virtually identical in the non-crossbar directions. Additional computational studies modeling still bigger handle structures are welcome, but the ability to precisely position SPM tips to the requisite atomic accuracy has been repeatedly demonstrated experimentally at low temperature, constituting a basic existence proof for this capability.

Further research to consider additional tooltips will require time-consuming computational chemistry
Computational chemistry
Computational chemistry is a branch of chemistry that uses principles of computer science to assist in solving chemical problems. It uses the results of theoretical chemistry, incorporated into efficient computer programs, to calculate the structures and properties of molecules and solids...

 and difficult laboratory work.

A working nanofactory would require a variety of well-designed tips for different reactions, and detailed analyses of placing atoms on more complicated surfaces. Although this appears a challenging problem given current resources, many tools will be available to help future researchers: Moore's Law
Moore's Law
Moore's law describes a long-term trend in the history of computing hardware: the number of transistors that can be placed inexpensively on an integrated circuit doubles approximately every two years....

 predicts further increases in computer power, semiconductor fabrication techniques continue to approach the nanoscale, and researchers grow ever more skilled at using proteins, ribosomes and DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 to perform novel chemistry.

Works of fiction

  • In The Diamond Age
    The Diamond Age
    The Diamond Age: Or, A Young Lady's Illustrated Primer is a postcyberpunk novel by Neal Stephenson. It is to some extent a science fiction bildungsroman, focused on a young girl named Nell, and set in a future world in which nanotechnology affects all aspects of life. The novel deals with themes of...

     by Neal Stephenson
    Neal Stephenson
    Neal Town Stephenson is an American writer known for his works of speculative fiction.Difficult to categorize, his novels have been variously referred to as science fiction, historical fiction, cyberpunk, and postcyberpunk...

     diamond can be constructed by simply building it out of carbon atoms. Also all sorts of devices from dust size detection devices to giant diamond zeppelins are constructed atom by atom using only carbon, oxygen, nitrogen and chlorine atoms.

  • In the novel Tomorrow by Andrew Saltzman (ISBN 1-4243-1027-X), a scientist uses nanorobotics
    Nanorobotics
    Nanorobotics is the emerging technology field of creating machines or robots whose components are at or close to the scale of a nanometer . More specifically, nanorobotics refers to the nanotechnology engineering discipline of designing and building nanorobots, with devices ranging in size from...

     to create a liquid that when inserted into the bloodstream, renders one nearly invincible
    Wiktionary
    Wiktionary is a multilingual, web-based project to create a free content dictionary, available in 158 languages...

     given that the microscopic machines repair tissue almost instantaneously after it is damaged.

  • In the manga series Battle Angel Alita
    Battle Angel Alita
    Battle Angel Alita, known in Japan as , is a manga series created by Yukito Kishiro in 1990 and originally published in Shueisha's Business Jump magazine. Two of the nine-volume comics were adapted into two anime original video animation episodes titled Battle Angel for North American release by...

     the scientist Desty Nova has specialized in molecular nanotechnology.

  • In the roleplaying game Splicers
    Splicers
    Splicers is a role-playing game using the Palladium Books Megaversal gaming system. The game is set in the midst of a war between humans and a world-wide computer intelligence alternately referred to as the N.E.X.U.S. or the Machine...

     by Palladium Books
    Palladium Books
    Palladium Books is a publisher of role-playing games perhaps best known for its popular, expansive Rifts series . Palladium was founded April 1981 in Detroit, Michigan by current president and lead game designer Kevin Siembieda, and is presently based in Westland, Michigan...

    , humanity has succumbed to a "nanobot plague" that causes any object made of a non-precious metal
    Precious metal
    A precious metal is a rare, naturally occurring metallic chemical element of high economic value.Chemically, the precious metals are less reactive than most elements, have high lustre, are softer or more ductile, and have higher melting points than other metals...

     to twist and change shape (sometimes into a type of robot
    Robot
    A robot is a mechanical or virtual intelligent agent that can perform tasks automatically or with guidance, typically by remote control. In practice a robot is usually an electro-mechanical machine that is guided by computer and electronic programming. Robots can be autonomous, semi-autonomous or...

    ) moments after being touched by a human. The object will then proceed to attack the human. This has forced humanity to develop "biotechnological" devices to replace those previously made of metal.

  • On the television show Mystery Science Theater 3000
    Mystery Science Theater 3000
    Mystery Science Theater 3000 is an American cult television comedy series created by Joel Hodgson and produced by Best Brains, Inc., that ran from 1988 to 1999....

    , the Nanites (voiced variously by Kevin Murphy
    Kevin Murphy (actor)
    Kevin Wagner Murphy is an American actor and writer best known as the voice and puppeteer of Tom Servo on the Peabody Award-winning comedy series Mystery Science Theater 3000.- Early career :...

    , Paul Chaplin, Mary Jo Pehl
    Mary Jo Pehl
    Mary Joseph Pehl born February 27, 1960 in Circle Pines, Minnesota, is an American writer, actress and comedienne. She is best known for her various roles on the television series Mystery Science Theater 3000.-Mystery Science Theater 3000:...

    , and Bridget Jones) - are self-replicating, bio-engineered organisms that work on the ship, they are microscopic creatures that reside in the Satellite of Love's computer systems. (They are similar to the creatures in Star Trek: The Next Generation
    Star Trek: The Next Generation
    Star Trek: The Next Generation is an American science fiction television series created by Gene Roddenberry as part of the Star Trek franchise. Roddenberry, Rick Berman, and Michael Piller served as executive producers at different times throughout the production...

    episode "Evolution
    Evolution (TNG episode)
    "Evolution" is the 49th episode of the science fiction television series Star Trek: The Next Generation.-Overview:In this episode, escaped nanites threaten the Federation Starfleet starship USS Enterprise as well as its critical research mission....

    ", which featured "nanites" taking over the Enterprise.) The Nanites made their first appearance in season 8. Based on the concept of nanotechnology
    Nanotechnology
    Nanotechnology is the study of manipulating matter on an atomic and molecular scale. Generally, nanotechnology deals with developing materials, devices, or other structures possessing at least one dimension sized from 1 to 100 nanometres...

    , their comical deus ex machina
    Deus ex machina
    A deus ex machina is a plot device whereby a seemingly inextricable problem is suddenly and abruptly solved with the contrived and unexpected intervention of some new event, character, ability, or object.-Linguistic considerations:...

    activities included such diverse tasks as instant repair and construction, hairstyling, performing a Nanite variation of a flea circus
    Flea circus
    A flea circus refers to a circus sideshow attraction in which fleas are attached to miniature carts and other items, and encouraged to perform circus acts within a small housing...

    , conducting a microscopic war, and even destroying the Observers' planet after a dangerously vague request from Mike to "take care of [a] little problem". They also ran a microbrewery
    Microbrewery
    A microbrewery or craft brewer is a brewery which produces a limited amount of beer, and is associated by consumers with innovation and uniqueness....

    .

See also

  • Nanotechnology in water treatment
    Nanotechnology in water treatment
    Nanotechnology, the engineering and art of manipulating matter at the nanoscale , offers the potential of novel nanomaterials for the treatment of surface water, groundwater and wastewater contaminated by toxic metal ions, organic and inorganic solutes and microorganisms...

  • Technomimetics
    Technomimetics
    Technomimetics are molecular systems that can mimic man-made devices. The term was first introduced in 1997. The current set of technomimetic molecules includes motors, rotors, gears, gyroscopes, tweezers, and other molecular devices. Technomimetics can be considered as the essential components of...


Reference works

  • The primary technical reference work on this topic is Nanosystems: Molecular Machinery, Manufacturing, and Computation, an in-depth, physics-based analysis of a particular class of potential nanomachines and molecular manufacturing systems, with extensive analyses of their feasibility and performance. Nanosystems is closely based on Drexler's MIT doctoral dissertation, "Molecular Machinery and Manufacturing with Applications to Computation". Both works also discuss technology development pathways that begin with scanning probe and biomolecular technologies.
  • Drexler and others extended the ideas of molecular nanotechnology with several other books. Unbounding the Future: the Nanotechnology Revolution and . Unbounding the Future is an easy-to-read book that introduces the ideas of molecular nanotechnology in a not-too-technical way. Other notable works in the same vein are Nanomedicine Vol. I and Vol. IIA by Robert Freitas
    Robert Freitas
    Robert A. Freitas Jr. is a Senior Research Fellow, one of four researchers at the nonprofit foundation Institute for Molecular Manufacturing in Palo Alto, California. He holds a 1974 Bachelor's degree majoring in both physics and psychology from Harvey Mudd College, and a 1978 Juris Doctor degree...

     and Kinematic Self-Replicating Machines by Robert Freitas
    Robert Freitas
    Robert A. Freitas Jr. is a Senior Research Fellow, one of four researchers at the nonprofit foundation Institute for Molecular Manufacturing in Palo Alto, California. He holds a 1974 Bachelor's degree majoring in both physics and psychology from Harvey Mudd College, and a 1978 Juris Doctor degree...

     and Ralph Merkle
    Ralph Merkle
    Ralph C. Merkle is a researcher in public key cryptography, and more recently a researcher and speaker on molecular nanotechnology and cryonics...

    .
  • Nanotechnology: Molecular Speculations on Global Abundance Edited by BC Crandall (ISBN 0-262-53137-2) offers interesting ideas for MNT applications.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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