Mechanosynthesis

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Mechanosynthesis is a term for hypothetical chemical syntheses in which reaction outcomes are determined by the use of mechanical constraints to direct reactive molecules to specific molecular sites. There are presently no non-biological chemical syntheses which achieve this aim. Some atomic placement has been achieved with scanning tunnelling microscopes.

Contents

Introduction

A ribosome is a biological machine. Protein translation.gif
A ribosome is a biological machine.

In conventional chemical synthesis or chemosynthesis, reactive molecules encounter one another through random thermal motion in a liquid or vapor. In a hypothesized process of mechanosynthesis, reactive molecules would be attached to molecular mechanical systems, and their encounters would result from mechanical motions bringing them together in planned sequences, positions, and orientations. It is envisioned that mechanosynthesis would avoid unwanted reactions by keeping potential reactants apart, and would strongly favor desired reactions by holding reactants together in optimal orientations for many molecular vibration cycles. In biology, the ribosome provides an example of a programmable mechanosynthetic device.

A non-biological form of mechanochemistry has been performed at cryogenic temperatures using scanning tunneling microscopes. [1] So far, such devices provide the closest approach to fabrication tools for molecular engineering. Broader exploitation of mechanosynthesis awaits more advanced technology for constructing molecular machine systems, with ribosome-like systems as an attractive early objective.

Much of the excitement regarding advanced mechanosynthesis regards its potential use in assembly of molecular-scale devices. Such techniques appear to have many applications in medicine, aviation, resource extraction, manufacturing and warfare.

Most theoretical explorations of advanced machines of this kind have focused on using carbon, because of the many strong bonds it can form, the many types of chemistry these bonds permit, and utility of these bonds in medical and mechanical applications. Carbon forms diamond, for example, which if cheaply available, would be an excellent material for many machines.

It has been suggested, notably by K. Eric Drexler, that mechanosynthesis will be fundamental to molecular manufacturing based on nanofactories capable of building macroscopic objects with atomic precision. The potential for these has been disputed, notably by Nobel Laureate Richard Smalley (who proposed and then critiqued an unworkable approach based on "Smalley fingers"). [2]

The Nanofactory Collaboration, [3] founded by Robert Freitas and Ralph Merkle in 2000, is a focused ongoing effort involving 23 researchers from 10 organizations and 4 countries that is developing a practical research agenda [4] specifically aimed at positionally controlled diamond mechanosynthesis and diamondoid nanofactory development.

In practice, getting exactly one molecule to a known place on the microscope's tip is possible, but has proven difficult to automate. Since practical products require at least several hundred million atoms, this technique has not yet proven practical in forming a real product.

The goal of one line of mechanoassembly research focuses on overcoming these problems by calibration, and selection of appropriate synthesis reactions. Some suggest attempting to develop a specialized, very small (roughly 1,000 nanometers on a side) machine tool that can build copies of itself using mechanochemical means, under the control of an external computer. In the literature, such a tool is called an assembler or molecular assembler. Once assemblers exist, geometric growth (directing copies to make copies) could reduce the cost of assemblers rapidly. Control by an external computer should then permit large groups of assemblers to construct large, useful projects to atomic precision. One such project would combine molecular-level conveyor belts with permanently mounted assemblers to produce a factory.

In part to resolve this and related questions about the dangers of industrial accidents and popular fears of runaway events equivalent to Chernobyl and Bhopal disasters, and the more remote issue of ecophagy, grey goo and green goo (various potential disasters arising from runaway replicators, which could be built using mechanosynthesis) the UK Royal Society and UK Royal Academy of Engineering in 2003 commissioned a study to deal with these issues and larger social and ecological implications, led by mechanical engineering professor Ann Dowling. This was anticipated by some to take a strong position on these problems and potentials —– and suggest any development path to a general theory of so-called mechanosynthesis. However, the Royal Society's nanotech report did not address molecular manufacturing at all, except to dismiss it along with grey goo.

Current technical proposals for nanofactories do not include self-replicating nanorobots, and recent ethical guidelines would prohibit development of unconstrained self-replication capabilities in nanomachines. [5] [6]

Diamond mechanosynthesis

There is a growing body of peer-reviewed theoretical work on synthesizing diamond by mechanically removing/adding hydrogen atoms [7] and depositing carbon atoms [8] [9] [10] [11] [12] [13] (a process known as diamond mechanosynthesis or DMS [14] ). For example, the 2006 paper in this 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 surface at both 300 K (room temperature) and 80 K (liquid nitrogen temperature), and that the silicon variant (DCB6Si) also works at 80 K but not at 300 K. These tooltips 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 paper III—tooltips must be positioned with great accuracy to avoid bonding the dimer incorrectly. Over 100,000 CPU hours were invested in this study.

The DCB6Ge tooltip motif, initially described 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. Although an early paper gives a predicted placement speed of 1 dimer per second for this tooltip, this limit was imposed by the slow speed of recharging the tool using an inefficient recharging method [10] and is not based on any inherent limitation in the speed of use of a charged tooltip. Additionally, no sensing means was proposed for discriminating among the three possible outcomes of an attempted dimer placement—deposition at the correct location, deposition at the wrong location, and failure to place the dimer at all—because the initial proposal was to position the tooltip by dead reckoning, with the proper reaction assured by designing appropriate chemical energetics and relative bond strengths for the tooltip-surface interaction.

More recent theoretical work [15] analyzes a complete set of nine molecular tools made from hydrogen, carbon and germanium able to (a) synthesize all tools in the set (b) recharge all tools in the set from appropriate feedstock molecules and (c) synthesize a wide range of stiff hydrocarbons (diamond, graphite, fullerenes, and the like). All required reactions are analyzed using standard ab initio quantum chemistry methods.

Further research [16] to consider alternate tips will require time-consuming computational chemistry and difficult laboratory work. In the early 2000s, a typical experimental arrangement was to attach a molecule to the tip of an atomic force microscope, and then use the microscope's precise positioning abilities to push the molecule on the tip into another on a substrate. Since the angles and distances can be precisely controlled, and the reaction occurs in a vacuum, novel chemical compounds and arrangements are possible.

History

The technique of moving single atoms mechanically was proposed by Eric Drexler in his 1986 book The Engines of Creation.

In 1989, researchers at IBM's Zürich Research Institute successfully spelled the letters "IBM" in xenon atoms on a cryogenic copper surface, grossly validating the approach. [1] [17] Since then, a number of research projects have undertaken to use similar techniques to store computer data in a compact fashion. More recently the technique has been used to explore novel physical chemistries, sometimes using lasers to excite the tips to particular energy states, or examine the quantum chemistry of particular chemical bonds.

In 1999, an experimentally proved methodology called feature-oriented scanning [18] [19] (FOS) was suggested. The feature-oriented scanning methodology allows precisely controlling the position of the probe of a scanning probe microscope (SPM) on an atomic surface at room temperature. The suggested methodology supports fully automatic control of single- and multiprobe instruments in solving tasks of mechanosynthesis and bottom-up nanofabrication.

In 2003, Oyabu et al. [20] reported the first instance of purely mechanical-based covalent bond-making and bond-breaking, i.e., the first experimental demonstration of true mechanosynthesis—albeit with silicon rather than carbon atoms.

In 2005, the first patent application on diamond mechanosynthesis [21] was filed.

In 2008, a $3.1 million grant was proposed [22] to fund the development of a proof-of-principle mechanosynthesis system.

In 2013, IBM made A Boy and His Atom, a short animated film using atoms. [23]

See also molecular nanotechnology, a more general explanation of the possible products, and discussion of other assembly techniques.

Related Research Articles

The following outline is provided as an overview of and topical guide to chemistry:

<span class="mw-page-title-main">Molecular nanotechnology</span> Technology

Molecular nanotechnology (MNT) is a technology based on the ability to build structures to complex, atomic specifications by means of mechanosynthesis. This is distinct from nanoscale materials. Based on Richard Feynman's vision of miniature factories using nanomachines to build complex products, this advanced form of nanotechnology would make use of positionally-controlled mechanosynthesis guided by molecular machine systems. MNT would involve combining physical principles demonstrated by biophysics, chemistry, other nanotechnologies, and the molecular machinery of life with the systems engineering principles found in modern macroscale factories.

<span class="mw-page-title-main">Nanotechnology</span> Field of applied science involving control of matter on atomic and (supra)molecular scales

Nanotechnology, often shortened to nanotech, is the use of matter on atomic, molecular, and supramolecular scales for industrial purposes. The earliest, widespread description of nanotechnology referred to the particular technological goal of precisely manipulating atoms and molecules for fabrication of macroscale products, also now referred to as molecular nanotechnology. A more generalized description of nanotechnology was subsequently established by the National Nanotechnology Initiative, which defined nanotechnology as the manipulation of matter with at least one dimension sized from 1 to 100 nanometers (nm). This definition reflects the fact that quantum mechanical effects are important at this quantum-realm scale, and so the definition shifted from a particular technological goal to a research category inclusive of all types of research and technologies that deal with the special properties of matter which occur below the given size threshold. It is therefore common to see the plural form "nanotechnologies" as well as "nanoscale technologies" to refer to the broad range of research and applications whose common trait is size.

<span class="mw-page-title-main">Molecular assembler</span> Proposed nanotechnological device

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". A molecular assembler is a kind of molecular machine. Some biological molecules such as ribosomes fit this definition. This is because they receive instructions from messenger RNA and then assemble specific sequences of amino acids to construct protein molecules. However, the term "molecular assembler" usually refers to theoretical human-made devices.

<span class="mw-page-title-main">Nanorobotics</span> Emerging technology field

Nanoid robotics, or for short, nanorobotics or nanobotics, is an emerging technology field creating machines or robots whose components are at or near 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 0.1 to 10 micrometres and constructed of nanoscale or molecular components. The terms nanobot, nanoid, nanite, nanomachine and nanomite have also been used to describe such devices currently under research and development.

<span class="mw-page-title-main">James Gimzewski</span> Scottish physicist of Polish descent

James Kazimierz Gimzewski FRS FREng FInstP is a Scottish physicist of Polish descent who pioneered research on electrical contacts with single atoms and molecules and light emission using scanning tunneling microscopy (STM).

The history of nanotechnology traces the development of the concepts and experimental work falling under the broad category of nanotechnology. Although nanotechnology is a relatively recent development in scientific research, the development of its central concepts happened over a longer period of time. The emergence of nanotechnology in the 1980s was caused by the convergence of experimental advances such as the invention of the scanning tunneling microscope in 1981 and the discovery of fullerenes in 1985, with the elucidation and popularization of a conceptual framework for the goals of nanotechnology beginning with the 1986 publication of the book Engines of Creation. The field was subject to growing public awareness and controversy in the early 2000s, with prominent debates about both its potential implications as well as the feasibility of the applications envisioned by advocates of molecular nanotechnology, and with governments moving to promote and fund research into nanotechnology. The early 2000s also saw the beginnings of commercial applications of nanotechnology, although these were limited to bulk applications of nanomaterials rather than the transformative applications envisioned by the field.

<span class="mw-page-title-main">Molecular biophysics</span> Interdisciplinary research area

Molecular biophysics is a rapidly evolving interdisciplinary area of research that combines concepts in physics, chemistry, engineering, mathematics and biology. It seeks to understand biomolecular systems and explain biological function in terms of molecular structure, structural organization, and dynamic behaviour at various levels of complexity. This discipline covers topics such as the measurement of molecular forces, molecular associations, allosteric interactions, Brownian motion, and cable theory. Additional areas of study can be found on Outline of Biophysics. The discipline has required development of specialized equipment and procedures capable of imaging and manipulating minute living structures, as well as novel experimental approaches.

<span class="mw-page-title-main">Nanoscopic scale</span> Structures with a length scale applicable to nanotechnology

The nanoscopic scale usually refers to structures with a length scale applicable to nanotechnology, usually cited as 1–100 nanometers (nm). A nanometer is a billionth of a meter. The nanoscopic scale is a lower bound to the mesoscopic scale for most solids.

The following outline is provided as an overview of and topical guide to nanotechnology:

The Technology Roadmap for Productive Nanosystems defines "productive nanosystems" as functional nanoscale systems that make atomically-specified structures and devices under programmatic control, i.e., they perform atomically precise manufacturing. Such devices are currently only hypothetical, and productive nanosystems represents a more advanced approach among several to perform Atomically Precise Manufacturing. A workshop on Integrated Nanosystems for Atomically Precise Manufacturing was held by the Dept. of Energy in 2015.

Molecular scale electronics, also called single-molecule electronics, is a branch of nanotechnology that uses single molecules, or nanoscale collections of single molecules, as electronic components. Because single molecules constitute the smallest stable structures imaginable, this miniaturization is the ultimate goal for shrinking electrical circuits.

<span class="mw-page-title-main">Nanoarchitectonics</span>

Nanoarchitectonics is a technology allowing to arrange nano-sized structural units, usually a group of atoms or molecules, in an intended configuration. It employs two major processes: nano-creation and nano-organization. Nano-organization involves re-arrangement of the structural units in a desired pattern, while nano-creation is synthesis of new materials that do not exist in nature. For example, by peeling atomic sheets off graphite slab, a novel nano-material graphene can be obtained, which has very different properties from graphite.

<span class="mw-page-title-main">Drexler–Smalley debate on molecular nanotechnology</span>

The Drexler–Smalley debate on molecular nanotechnology was a public dispute between K. Eric Drexler, the originator of the conceptual basis of molecular nanotechnology, and Richard Smalley, a recipient of the 1996 Nobel prize in Chemistry for the discovery of the nanomaterial buckminsterfullerene. The dispute was about the feasibility of constructing molecular assemblers, which are molecular machines which could robotically assemble molecular materials and devices by manipulating individual atoms or molecules. The concept of molecular assemblers was central to Drexler's conception of molecular nanotechnology, but Smalley argued that fundamental physical principles would prevent them from ever being possible. The two also traded accusations that the other's conception of nanotechnology was harmful to public perception of the field and threatened continued public support for nanotechnology research.

<span class="mw-page-title-main">Don Eigler</span>

Donald M. Eigler is an American physicist associated with the IBM Almaden Research Center, who is noted for his achievements in nanotechnology.

Atomically precise manufacturing (APM) is an application of nanotechnology where single molecules can be used to manufacture products at an atomic level. The technology currently has potential in highly technical fields like quantum computing, but if commercialized, it would likely have a major impact across all fields of manufacturing. APM is classified as a disruptive technology, or a technology that creates large amounts of change in an existing industry.

A probe tip is an instrument used in scanning probe microscopes (SPMs) to scan the surface of a sample and make nano-scale images of surfaces and structures. The probe tip is mounted on the end of a cantilever and can be as sharp as a single atom. In microscopy, probe tip geometry and the composition of both the tip and the surface being probed directly affect resolution and imaging quality. Tip size and shape are extremely important in monitoring and detecting interactions between surfaces. SPMs can precisely measure electrostatic forces, magnetic forces, chemical bonding, Van der Waals forces, and capillary forces. SPMs can also reveal the morphology and topography of a surface.

<span class="mw-page-title-main">Center for Chemistry at the Space-Time Limit</span>

Center for Chemistry at the Space-Time Limit or CaSTL Center is a National Science Foundation Center for Chemical Innovation.

This glossary of nanotechnology is a list of definitions of terms and concepts relevant to nanotechnology, its sub-disciplines, and related fields.

Artificial lattice is a term encompassing every atomic-scale structures designed and controlled to confine electrons onto a chosen lattice. Research has been done on multiple geometries and one of the most notable being what is called molecular graphene. Molecular graphene is a part of two-dimensional artificial lattices.

References

  1. 1 2 Eigler, D. M.; Schweizer, E. K. (April 1990). "Positioning single atoms with a scanning tunnelling microscope". Nature. 344 (6266): 524–526. doi:10.1038/344524a0. ISSN   0028-0836.
  2. ↑ Baum, Rudy (2003-12-01). "Drexler and Smalley make the case for and against 'molecular assemblers'". Chemical & Engineering News. 81 (48): 27–42. ISSN   0009-2347.
  3. ↑ Nanofactory Collaboration. Molecularassembler.com. Retrieved on 2011-07-23.
  4. ↑ Nanofactory Technical Challenges. Molecularassembler.com. Retrieved on 2011-07-23.
  5. ↑ Molecular Nanotechnology Guidelines. Foresight.org. Retrieved on 2011-07-23.
  6. ↑ N04FR06-p.15.pmd. (PDF) . Retrieved on 2011-07-23.
  7. ↑ Temelso, Berhane; Sherrill, C. David; Merkle, Ralph C.; Freitas, Robert A. (2006). "High-level Ab Initio Studies of Hydrogen Abstraction from Prototype Hydrocarbon Systems" (PDF). The Journal of Physical Chemistry A. 110 (38): 11160–11173. Bibcode:2006JPCA..11011160T. CiteSeerX   10.1.1.154.7331 . doi:10.1021/jp061821e. PMID   16986851.
  8. ↑ Merkle, RC; Freitas Jr, RA (2003). "Theoretical Analysis of a Carbon-Carbon Dimer Placement Tool for Diamond Mechanosynthesis" (PDF). Journal of Nanoscience and Nanotechnology. 3 (4): 319–24. doi:10.1166/jnn.2003.203. PMID   14598446.
  9. ↑ Peng, Jingping; Freitas, Robert A.; Merkle, Ralph C. (2004). "Theoretical Analysis of Diamond Mechanosynthesis. Part I. Stability of C2 Mediated Growth of Nanocrystalline Diamond C(110) Surface" (PDF). Journal of Computational and Theoretical Nanoscience. 1: 62–70. doi:10.1166/jctn.2004.007. Archived from the original (PDF) on 2009-03-16.
  10. 1 2 Mann, David J.; Peng, Jingping; Freitas, Robert A.; Merkle, Ralph C. (2004). "Theoretical Analysis of Diamond Mechanosynthesis. Part II. C2 Mediated Growth of Diamond C(110) Surface via Si/Ge-Triadamantane Dimer Placement Tools" (PDF). Journal of Computational and Theoretical Nanoscience. 1: 71–80. doi:10.1166/jctn.2004.008.
  11. ↑ Sourina, Olga; Korolev, Nikolay (2005). "Design and Analysis of a Molecular Tool for Carbon Transfer in Mechanosynthesis" (PDF). Journal of Computational and Theoretical Nanoscience. 2 (4): 492–498. Bibcode:2005JCTN....2..492S. doi:10.1166/jctn.2005.003.
  12. ↑ De Federico, Miguel; Jaime, Carlos (2006). "Theoretical Analysis of Diamond Mechanosynthesis. Part III. Positional C2 Deposition on Diamond C(110) Surface using Si/Ge/Sn-based Dimer Placement Tools" (PDF). Journal of Computational and Theoretical Nanoscience. 3 (6): 874–879. arXiv: cond-mat/0605239 . Bibcode:2006JCTN....3..624S. doi:10.1166/jctn.2006.003.
  13. ↑ Yin, Zhi-Xiang; Cui, Jian-Zhong; Liu, Wenbin; Shi, Xiao-Hong; Xu, Jin (2007). "Horizontal Ge-Substituted Polymantane-Based C2 Dimer Placement Tooltip Motifs for Diamond Mechanosynthesis" (PDF). Journal of Computational and Theoretical Nanoscience. 4 (7): 1243–1248. doi:10.1166/jctn.2007.004.
  14. ↑ Diamond Mechanosynthesis. Molecularassembler.com. Retrieved on 2011-07-23.
  15. ↑ Freitas Jr., Robert A.; Merkle, Ralph C. (2008). "A Minimal Toolset for Positional Diamond Mechanosynthesis" (PDF). Journal of Computational and Theoretical Nanoscience. 5 (7): 760–861. Bibcode:2008JCTN....5..760F. doi:10.1166/jctn.2008.2531.
  16. ↑ Speeding the development of molecular nanotechnology. www.foresight.org
  17. ↑ Shankland, S. (28 September 2009). "IBM's 35 atoms and the rise of nanotech". CNET. Retrieved 2023-05-09.
  18. ↑ R. V. Lapshin (2004). "Feature-oriented scanning methodology for probe microscopy and nanotechnology" (PDF). Nanotechnology. 15 (9): 1135–1151. Bibcode:2004Nanot..15.1135L. doi:10.1088/0957-4484/15/9/006. ISSN   0957-4484. (Russian translation is available).
  19. ↑ R. V. Lapshin (2011). "Feature-oriented scanning probe microscopy". In H. S. Nalwa (ed.). Encyclopedia of Nanoscience and Nanotechnology (PDF). Vol. 14. USA: American Scientific Publishers. pp. 105–115. ISBN   978-1-58883-163-7.
  20. ↑ Oyabu, Noriaki; Custance, ÓScar; Yi, Insook; Sugawara, Yasuhiro; Morita, Seizo (2003). "Mechanical Vertical Manipulation of Selected Single Atoms by Soft Nanoindentation Using Near Contact Atomic Force Microscopy". Physical Review Letters. 90 (17): 176102. Bibcode:2003PhRvL..90q6102O. doi: 10.1103/PhysRevLett.90.176102 . PMID   12786084.
  21. ↑ Robert A. Freitas Jr., "A Simple Tool for Positional Diamond Mechanosynthesis, and its Method of Manufacture," U.S. Patent 7,687,146 , issued 30 March 2010 HTML copy Retrieved on 2011-07-23.
  22. ↑ Digital Matter?: Towards Mechanised Mechanosynthesis Archived 2011-11-04 at the Wayback Machine . Gow.epsrc.ac.uk. Retrieved on 2011-07-23.
  23. ↑ "A Boy And His Atom". IBM Research. May 1, 2013. Retrieved December 29, 2015.
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