Editing Molecular nanotechnology (section)

==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''<ref name="nanotechnology1">{{cite book|url=http://www.nap.edu/catalog/11752.html |title=A Matter of Size: Triennial Review of the National Nanotechnology Initiative |publisher=Nap.edu |access-date=2010-09-05|doi=10.17226/11752 |year=2006 |isbn=978-0-309-10223-0 }}</ref> 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]]'' reads<ref>{{cite web|url=http://www.e-drexler.com/d/06/00/EOC/EOC_Cover.html |title=Engines of Creation - K. Eric Drexler : Cover |publisher=E-drexler.com |access-date=2010-09-05}}</ref> "Universal Assemblers", and the following text speaks of multiple types of [[Assembler (nanotechnology)|assemblers]] which, collectively, could hypothetically "build almost anything that the laws of nature allow to exist." Drexler's colleague [[Ralph Merkle]] has noted that, contrary to widespread legend,<ref>{{cite web|url=http://www.foresight.org/impact/impossible.html#Fear |title=How good scientists reach bad conclusions |publisher=Foresight.org |access-date=2010-09-05}}</ref> 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'',<ref>{{cite web|url=http://www.e-drexler.com/d/06/00/Nanosystems/toc.html |title=Nanosystems TOC |publisher=E-drexler.com |date=2002-11-01 |access-date=2010-09-05}}</ref> a detailed proposal for synthesizing stiff covalent structures using a table-top factory. [[Diamondoid]] structures and other stiff covalent structures, if achieved, would have a wide range of possible applications, going far beyond current [[Microelectromechanical systems|MEMS]] 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 <ref name="autogenerated3" /> 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 advocated by Drexler) as a deterministic/mechanistic idea of nano engineered  machines that does not take into account the nanoscale challenges such as [[wetness]], [[Adhesion|stickiness]], [[Brownian motion]], and high [[viscosity]]. He also explains what is soft nanotechnology or more appropriately [[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{{ndash}}Drexler debate===
{{main|Drexler–Smalley debate on molecular nanotechnology}}

Several researchers, including Nobel Prize winner [[Richard Smalley|Dr. Richard Smalley]] (1943–2005),<ref>{{cite journal| url=http://www.sciamdigital.com/index.cfm?fa=Products.ViewIssuePreview&ARTICLEID_CHAR=F90C4210-C153-4B2F-83A1-28F2012B637| date=September 2001| journal=Scientific American| title=Of Chemistry, Love and Nanobots| first=Richard E.| last=Smalley| doi=10.1038/scientificamerican0901-76| pmid=11524973| volume=285| issue=3| pages=76–77| bibcode=2001SciAm.285c..76S| access-date=2007-04-15| archive-url=https://web.archive.org/web/20120723062135/http://www.sciamdigital.com/index.cfm?fa=Products.ViewIssuePreview&ARTICLEID_CHAR=F90C4210-C153-4B2F-83A1-28F2012B637| archive-date=2012-07-23| url-status=dead}}</ref> attacked the notion of universal assemblers, leading to a rebuttal from Drexler and colleagues,<ref>{{cite web|url=http://www.imm.org/SciAmDebate2/smalley.php |title=Debate About Assemblers — Smalley Rebuttal |publisher=Imm.org |access-date=2010-09-05}}</ref> and eventually to an exchange of letters.<ref>{{cite web|url=http://pubs.acs.org/cen/coverstory/8148/8148counterpoint.html |title=C&En: Cover Story - Nanotechnology |publisher=Pubs.acs.org |date=2003-12-01 |access-date=2010-09-05}}</ref> 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. It is noteworthy that, contrary to Smalley's opinion that enzymes require water, "Not only do enzymes work vigorously in anhydrous organic media, but in this unnatural milieu they acquire remarkable properties such as greatly enhanced stability, radically altered substrate and [[enantiomeric]] specificities, molecular memory, and the ability to catalyse unusual reactions."<ref>{{cite journal|title=Enzymatic catalysis in anhydrous organic solvents.|date=April 1989 | pmid=2658221 | doi=10.1016/0968-0004(89)90146-1|volume=14|issue=4 |journal=Trends Biochem Sci|pages=141–4 | last1 = Klibanov | first1 = AM}}"{{cite journal|title=Enzymatic catalysis in anhydrous organic solvents|date=April 1989 | pmc=397741|pmid=3858815|volume=82|issue = 10|journal=Proc. Natl. Acad. Sci. U.S.A.|pages=3192–6 | last1 = Zaks | first1 = A | last2 = Klibanov | first2 = AM|doi=10.1073/pnas.82.10.3192 |bibcode=1985PNAS...82.3192Z|doi-access=free }}</ref>

===Redefining of the word "nanotechnology"===
For the future, some means have 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 (author)|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."<ref name="JohGall2">{{Cite book |last=Gall |first=John |url=https://archive.org/details/systemantics00john/page/80/ |title=Systemantics: How Systems Work and Especially How They Fail |publisher=Pocket Books |year=1978 |isbn=9780671819101 |edition=1st |location=New York |pages=80–81 |author-link=John Gall (author) |via=[[Archive.org]]}}</ref> 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"
<ref name = "Dawkins">
Richard Dawkins, The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe Without Design, W. W. Norton; Reissue edition (September 19, 1996)
</ref> 
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]] 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 [[scanning tunneling microscope|STM]] or [[Atomic force microscope|AFM]] 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''===
{{Multiple image
|direction = vertical
|image1 = Molecularpropeller.jpg
|image2 = Nanob.jpg
|footer = Top, a molecular propellor. Bottom, a molecular [[planetary gear]] system. The feasibility of devices like these has been questioned.}}

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<ref>{{cite web|url=http://www.softmachines.org/wordpress/index.php?p=50#comment-523 |title=Blog Archive » Is mechanosynthesis feasible? The debate moves up a gear |publisher=Soft Machines |date=2004-12-16 |access-date=2010-09-05}}</ref> 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.<ref>{{cite magazine|url=https://www.wired.com/wired/archive/12.10/drexler.html |title=Smalley |magazine=Wired |date= October 2004|access-date=2010-09-05|last1=Regis |first1=Ed }}</ref><ref>{{cite web|url=http://www.nanotech-now.com/Atkinson-Phoenix-Nanotech-Debate.htm |title=Atkinson |publisher=Nanotech-now.com |access-date=2010-09-05}}</ref><ref>{{cite web|url=http://www.softmachines.org/wordpress/index.php?p=70 |title=Moriarty |publisher=Softmachines.org |date=2005-01-26 |access-date=2010-09-05}}</ref><ref>{{cite web|url=http://www.softmachines.org/wordpress/?p=175 |title=Jones |publisher=Softmachines.org |date=2005-12-18 |access-date=2010-09-05}}</ref> 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 <ref>{{cite web|url=http://www.MolecularAssembler.com/Nanofactory/Publications.htm |title=Nanofactory Collaboration Publications |publisher=Molecularassembler.com |access-date=2010-09-05}}</ref> 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]] 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]] systems. We are now in a position like that of the [[British Interplanetary Society]] 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."<ref>{{cite web|url=http://www.softmachines.org/PDFs/Moriarty_Phoenix_1.pdf |title=Moriarity Correspondence |access-date=2010-09-05}}</ref>  However, Freitas and Merkle argue <ref>{{cite web|url=http://www.MolecularAssembler.com/Nanofactory/index.htm#NeedFund |title=Nanofactory Collaboration |publisher=Molecularassembler.com |access-date=2010-09-05}}</ref> 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.<ref name="autogenerated2" />

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 [[molecular design software]] and editing tools that have been developed, e.g., at Nanorex,<ref>{{cite web|url=http://nanoengineer-1.com/content/index.php?option=com_content&task=view&id=40&Itemid=50 |title=Nanorex, Inc. - Molecular Machinery Gallery |publisher=Nanoengineer-1.com |access-date=2010-09-05}}</ref> or the newer ''Molecular Science and Engineering Platform One'' (MSEP.one).<ref>{{cite web |last1=Drexler |first1=K. Eric |last2=van Braam |first2=H.P. |last3=Ackley |first3=Jonathan |last4=Grzesik |first4=Jakub |last5=Suligoy |first5=Mariano |last6=Mancevics |first6=Janis |last7=Alves |first7=Bruno |url=https://msep.one/ |title=Molecular Systems and Engineering Platform (MSEP.one) |website=MSEP.one |access-date=28 February 2025}}</ref><ref>{{cite web |last1=Drexler |first1=K. Eric |display-authors=etal |date=4 October 2024 |url=https://github.com/MSEP-one |title=MSEP.one: Molecular Science and Engineering Platform One |website=[[GitHub]] |access-date=28 February 2025}}</ref>

In the latest report ''A Matter of Size: Triennial Review of the National Nanotechnology Initiative''<ref name="nanotechnology1"/> 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.<ref>{{cite web|url=http://www.MolecularAssembler.com/Nanofactory/DMS.htm |title=Diamond Mechanosynthesis |publisher=Molecularassembler.com |access-date=2010-09-05}}</ref>  The "Technology Roadmap for [[Productive nanosystems|Productive Nanosystems]]"<ref>{{cite web|url=http://www.foresight.org/roadmaps |title=Technology Roadmap for Productive Nanosystems |publisher=Foresight.org |access-date=2010-09-05}}</ref> 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]] 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."<ref>[[Wikiquote:Richard Feynman]]</ref>

===Existing work on diamond mechanosynthesis===

There is a growing body of peer-reviewed theoretical work on synthesizing diamond by mechanically removing/adding hydrogen atoms <ref>[http://www.MolecularAssembler.com/Papers/TemelsoHAbst.pdf High-level Ab Initio Studies of Hydrogen Abstraction from Prototype Hydrocarbon Systems]. Temelso, Sherrill, Merkle, and Freitas, ''J. Phys. Chem. A'' Vol. 110, pages 11160-11173, 2006.</ref> and depositing carbon atoms <ref>[http://www.rfreitas.com/Nano/JNNDimerTool.pdf Theoretical Analysis of a Carbon-Carbon Dimer Placement Tool for Diamond Mechanosynthesis]. Merkle and Freitas, ''J. Nanosci. Nanotech.'' Vol. 3, pages 319-324, 2003.</ref><ref>[http://www.MolecularAssembler.com/JCTNPengMar04.pdf Theoretical Analysis of Diamond Mechanosynthesis. Part I. Stability of C<sub>2</sub> Mediated Growth of Nanocrystalline Diamond C(110) Surface] {{webarchive|url=https://web.archive.org/web/20090316022613/http://www.molecularassembler.com/JCTNPengMar04.pdf |date=2009-03-16 }}. Peng, Freitas and Merkle. ''J. Comput. Theor. Nanosci.'' Vol. 1, pages 62-70, 2004.</ref><ref>[http://www.MolecularAssembler.com/JCTNMannMar04.pdf Theoretical Analysis of Diamond Mechanosynthesis. Part II. C<sub>2</sub> Mediated Growth of Diamond C(110) Surface via Si/Ge-Triadamantane Dimer Placement Tools] {{webarchive|url=https://web.archive.org/web/20090316022605/http://www.molecularassembler.com/JCTNMannMar04.pdf |date=2009-03-16 }}. Mann, Peng, Freitas and Merkle. ''J. Comput. Theor. Nanosci.'' Vol. 1, pages 71-80, 2004.</ref><ref>[http://e-drexler.com/d/05/00/DC10C-mechanosynthesis.pdf Design and Analysis of a Molecular Tool for Carbon Transfer in Mechanosynthesis]. Allis and Drexler. ''J. Comput. Theor. Nanosci.'' Vol. 2, pages 71-80, 2005.</ref><ref>[http://www.MolecularAssembler.com/Papers/JCTNPengFeb06.pdf Theoretical Analysis of Diamond Mechanosynthesis. Part III. Positional C<sub>2</sub> Deposition on Diamond C(110) Surface using Si/Ge/Sn-based Dimer Placement Tools]. Peng, Freitas, Merkle, Von Ehr, Randall and Skidmore. ''J. Comput. Theor. Nanosci.'' Vol. 3, pages 28-41, 2006.</ref><ref>[Horizontal Ge-Substituted Polymantane-Based C<sub>2</sub> Dimer Placement Tooltip Motifs for Diamond Mechanosynthesis]. Freitas, Allis and Merkle. ''J. Comput. Theor. Nanosci.'' Vol. 4, 2007, in press.</ref> (a process known as [[mechanosynthesis]]). This work is slowly permeating the broader nanoscience community and is being critiqued.  For instance, Peng et al. (2006)<ref>{{cite web|url=http://www.MolecularAssembler.com/Papers/JCTNPengFeb06.pdf |title=03CTN01-003 |access-date=2010-09-05}}</ref> (in the continuing research effort by Freitas, Merkle and their collaborators) reports that the most-studied mechanosynthesis tooltip motif (DCB6Ge) successfully places a C<sub>2</sub> carbon [[Dimer (chemistry)|dimer]] on a C(110) [[diamond]] surface at both 300&nbsp;K (room temperature) and 80&nbsp;K ([[liquid nitrogen]] temperature), and that the silicon variant (DCB6Si) also works at 80&nbsp;K but not at 300&nbsp;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.&nbsp;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&nbsp;THz to 1.8&nbsp;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. More computed 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,<ref>{{cite web|url=http://www.physics.uci.edu/~wilsonho/stm-iets.html |title=Wilson Ho |publisher=Physics.uci.edu |access-date=2010-09-05}}</ref><ref>{{cite journal|journal=[[Physical Review Letters]]|volume=90|issue=17|page=176102|doi= 10.1103/PhysRevLett.90.176102|bibcode=2003PhRvL..90q6102O|title=Mechanical Vertical Manipulation of Selected Single Atoms by Soft Nanoindentation Using Near Contact Atomic Force Microscopy |pmid=12786084 |last1=Oyabu |first1=N. |last2=Custance |first2=O. |last3=Yi |first3=I. |last4=Sugawara |first4=Y. |last5=Morita |first5=S. |year=2003 |doi-access=free}}</ref> or even at room temperature<ref>{{cite journal |last1=Lapshin |first1=R. V. |year=2004 |title=Feature-oriented scanning methodology for probe microscopy and nanotechnology|journal=Nanotechnology|volume=15|issue=9|pages=1135–1151|issn=0957-4484|doi=10.1088/0957-4484/15/9/006|url=http://www.lapshin.fast-page.org/publications.htm#feature2004|format=PDF|bibcode=2004Nanot..15.1135L}}</ref><ref>{{cite book|author=R. V. Lapshin|year=2011|contribution=Feature-oriented scanning probe microscopy|title=Encyclopedia of Nanoscience and Nanotechnology|editor=H. S. Nalwa|volume=14|pages=105–115|publisher=American Scientific Publishers|location=USA|isbn=978-1-58883-163-7|url=http://www.lapshin.fast-page.org/publications.htm#fospm2011|format=PDF}}</ref> constituting a basic existence proof for this capability.

Further research<ref>{{cite web|url=http://www.MolecularAssembler.com/Nanofactory/AnnBibDMS.htm |title=DMS Bibliography |publisher=Molecularassembler.com |access-date=2010-09-05}}</ref> to consider additional tooltips will require time-consuming [[computational chemistry]] 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]] predicts further increases in computer power, [[Fabrication (semiconductor)|semiconductor fabrication]] techniques continue to approach the nanoscale, and researchers grow ever more skilled at using [[protein]]s, [[ribosome]]s and [[DNA]] to perform novel chemistry.