Editing Nanotechnology (section)

===Molecular nanotechnology: a long-term view===
{{Main|Molecular nanotechnology}}

Molecular nanotechnology, sometimes called molecular manufacturing, concerns engineered nanosystems (nanoscale machines) operating on the molecular scale. Molecular nanotechnology is especially associated with [[molecular assembler]]s, machines that can produce a desired structure or device atom-by-atom using the principles of [[mechanosynthesis]]. Manufacturing in the context of [[productive nanosystems]] is not related to conventional technologies used to manufacture nanomaterials such as carbon nanotubes and nanoparticles.

When Drexler independently coined and popularized the term "nanotechnology", he envisioned manufacturing technology based on [[molecular machine]] systems. The premise was that molecular-scale biological analogies of traditional machine components demonstrated molecular machines were possible: biology was full of examples of sophisticated, [[stochastic]]ally optimized [[Molecular machine#Biological|biological machines]].

Drexler and other researchers<ref>{{cite web| vauthors = Phoenix C |date=March 2005|url=http://www.crnano.org/developing.htm|title=Nanotechnology: Developing Molecular Manufacturing|archive-url=https://web.archive.org/web/20200601095107/http://www.crnano.org/developing.htm|archive-date=2020-06-01}}. crnano.org</ref> have proposed that advanced nanotechnology ultimately could be based on mechanical engineering principles, namely, a manufacturing technology based on the mechanical functionality of these components (such as gears, bearings, motors, and structural members) that would enable programmable, positional assembly to atomic specification.<ref>{{cite web|url=http://www.imm.org/PNAS.html|title=Some papers by K. Eric Drexler|work=imm.org|url-status=live|archive-url=https://web.archive.org/web/20060411075149/http://www.imm.org/PNAS.html|archive-date=2006-04-11}}</ref> The physics and engineering performance of exemplar designs were analyzed in Drexler's book ''Nanosystems: Molecular Machinery, Manufacturing, and Computation''.<ref name=Nanotsystems />

In general, assembling devices on the atomic scale requires positioning atoms on other atoms of comparable size and stickiness. [[Carlo Montemagno]]'s view is that future nanosystems will be hybrids of silicon technology and biological molecular machines.<ref>{{cite web |title=Carlo Montemagno, Ph.D. |url=http://www.cnsi.ucla.edu/institution/personnel?personnel%5fid=105488 |archive-url=https://web.archive.org/web/20141008065938/http://faculty.cnsi.ucla.edu/institution/personnel?personnel%5fid=105488 |archive-date=2014-10-08 |website=California NanoSystems Institute (CNSI), University of California, Los Angeles (UCLA)}}</ref> [[Richard Smalley]] argued that mechanosynthesis was impossible due to difficulties in mechanically manipulating individual molecules.<ref>{{Cite journal |last=Smalley |first=Richard E. |date=2001 |title=Of Chemistry, Love and Nanobots |url=https://www.jstor.org/stable/26059339 |journal=Scientific American |volume=285 |issue=3 |pages=76–77 |doi=10.1038/scientificamerican0901-76 |jstor=26059339 |pmid=11524973 |bibcode=2001SciAm.285c..76S |issn=0036-8733}}</ref>

This led to an exchange of letters in the [[American Chemical Society|ACS]] publication [[Chemical & Engineering News]] in 2003.<ref>{{cite journal | vauthors = Baum R |url=http://pubs.acs.org/cen/coverstory/8148/8148counterpoint.html|title=Cover Story – Nanotechnology|date=December 1, 2003|volume=81|issue=48|journal=Chemical and Engineering News|pages=37–42}}</ref> Though biology clearly demonstrates that molecular machines are possible, non-biological molecular machines remained in their infancy. [[Alex Zettl]] and colleagues at Lawrence Berkeley Laboratories and UC Berkeley<ref>{{cite web|url=http://research.physics.berkeley.edu/zettl/|archive-url=https://web.archive.org/web/20151008062820/http://research.physics.berkeley.edu/zettl/|archive-date=2015-10-08|title=Zettl Research Group |publisher=Department of Physics, University of California, Berkeley}}</ref> constructed at least three molecular devices whose motion is controlled via changing voltage: a nanotube [[nanomotor]], a molecular actuator,<ref>{{cite journal | vauthors = Regan BC, Aloni S, Jensen K, Ritchie RO, Zettl A | title = Nanocrystal-powered nanomotor | journal = Nano Letters | volume = 5 | issue = 9 | pages = 1730–3 | date = September 2005 | pmid = 16159214 | doi = 10.1021/nl0510659 | url = http://www.physics.berkeley.edu/research/zettl/pdf/312.NanoLett5regan.pdf | url-status = dead | osti = 1017464 | bibcode = 2005NanoL...5.1730R | archive-url = https://web.archive.org/web/20060510143208/http://www.physics.berkeley.edu/research/zettl/pdf/312.NanoLett5regan.pdf | archive-date = 2006-05-10 }}</ref> and a nanoelectromechanical relaxation oscillator.<ref>{{cite journal|url=http://www.lbl.gov/Science-Articles/Archive/sabl/2005/May/Tiniest-Motor.pdf|doi=10.1063/1.1887827|title=Surface-tension-driven nanoelectromechanical relaxation oscillator|year=2005| vauthors = Regan BC, Aloni S, Jensen K, Zettl A |journal=Applied Physics Letters |volume=86 |page=123119 |bibcode=2005ApPhL..86l3119R|issue=12|url-status=live|archive-url=https://web.archive.org/web/20060526193318/http://www.lbl.gov/Science-Articles/Archive/sabl/2005/May/Tiniest-Motor.pdf|archive-date=2006-05-26}}</ref>

Ho and Lee at [[Cornell University]] in 1999 used a scanning tunneling microscope to move an individual carbon monoxide molecule (CO) to an individual iron atom (Fe) sitting on a flat silver crystal and chemically bound the CO to the Fe by applying a voltage.<ref>{{Cite journal |last1=Lee |first1=H. J. |last2=Ho |first2=W. |date=1999-11-26 |title=Single-Bond Formation and Characterization with a Scanning Tunneling Microscope |url=https://www.science.org/doi/10.1126/science.286.5445.1719 |journal=Science |language=en |volume=286 |issue=5445 |pages=1719–1722 |doi=10.1126/science.286.5445.1719 |pmid=10576735 |issn=0036-8075}}</ref>