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The Drexler–Smalley debate on molecular nanotechnology was a public dispute between K. Eric Drexler, founder of the field of molecular nanotechnology, and Richard Smalley, a recipient of the 1996 Nobel prize in Chemistry for the discovery of the nanomaterial buckminsterfullerene, about the feasibility of constructing molecular assemblers. The debate was carried out from 2001 to 2003 through a series of published articles and open letters. The debate is often cited in the history of nanotechnology due to the fame of its participants, its commentary on both the technical and social aspects of nanotechnology, and its adversarial tone.

The participants

K. Eric Drexler

K. Eric Drexler was the first person to develop the concepts of nanotechnology and was a key figure in popularizing these concepts. Trained as an engineer, Drexler was inspired by a then-obscure 1959 talk by physicist Richard Feynman called There's Plenty of Room at the Bottom, which posited that it should be physically possible to manipulate individual atoms using top-down engineering methodologies. Drexler was also inspired by recent advances in molecular biology such as recombinant DNA technology. In a 1981 publication in Proceedings of the National Academy of Sciences, considered to be the first journal article on nanotechnology, he argued that biological systems such as the ribosome were already capable of building molecules atom-by-atom, and that artificial machines with this capability could also be constructed. Drexler went on to publish two books on nanotechnology: Engines of Creation in 1986, which was intended for the public, and the technical work Nanosystems in 1992. He also co-founded the Foresight Institute, a public interest group devoted to increasing public awareness and information about molecular nanotechnology.

Drexler's vision of nanotechnology, now called molecular nanotechnology, is based on the concept of the molecular assembler, a molecular machine which would manufacture molecules and molecular devices atom-by-atom. Drexler drew a distinction between wet nanotechnology based on biological systems, and "second-generation" dry nanotechnology which would be based on mechanosynthesis, positional control of molecules through principles more related to mechanical engineering. Drexler and his followers have focused almost exclusively on the latter form of molecular nanotechnology, but Drexler has stated that both are valid pathways to creating molecular machine systems.

Richard Smalley

Richard E. Smalley, a chemist at Rice University, is best known as a co-discoverer of the C₆₀ form of carbon known as buckminsterfullerine in 1985, along with Harry Kroto, Robert Curl, James Heath, and Sean O'Brien. Buckminsterfullerene was the first to be discovered of the class of molecules known as fullerenes, which also includes carbon nanotubes. The study and application of fullerenes forms a significant part of the fields of nanomaterials and nanoelectronics, and Smalley, Kroto, and Curl were awarded the 1996 Nobel Prize in Chemistry for their discovery of buckminsterfullerene. Smalley had also taken a prominent public policy role in relation to nanotechnology, and was an outspoken advocate for using nanotechnology to develop solutions to the world's energy and health problems, for example raising the possibility of using nanomaterials for efficient energy storage and transmission, and of developing nanomaterial-based drugs for targeted drug delivery.

The debate

Smalley's Scientific American article

Smalley wrote an article, "Of Chemistry, Love, and Nanobots", for the September 2001 issue of the popular science magazine Scientific American, which was a special issue on the topic of nanotechnology. Smalley opened by comparing a chemical reaction to an intricate dance of atoms:

"When a boy and a girl fall in love, it is often said that the chemistry between them is good. This common use of the word 'chemistry' in human relations comes close to the subtlety of what actually happens in the more mundane coupling of molecules. In a chemical reaction between two 'consenting' molecules, bonds form between some of the atoms in what is usually a complex dance involving motion in multiple dimensions.... And if the chemistry is really, really good, the molecules that do react will all produce the exact product required."

He then referenced the idea of a molecular assembler, a nanorobot capable of manipulating individual atoms to build a desired product. He posed the question of how long it would take such an assembler to produce a meaningful amount of material; for one assembler he estimated that it would take millions of years to produce one mole of material, but if the assembler were allowed to self-replicate, a large ensemble of assemblers could be created in a minute which would then be capable of producing a mole of product in a fraction of a millisecond. Smalley then talks about the implications of this result and the fears that have been arisen about it, namely the fear that the nanorobots could mutate and reproduce indefinately, causing a grey goo scenario, or, referring to Bill Joy's previous article "Why the future doesn't need us", that the nanorobots could develop swarm intelligence and become alive in some sense.

Smalley then asks how realistic the concept of a self-replicating nanorobot is. He states that, in a chemical reaction, the chemical bonds are all interconnected and that the placement of each atom is sensitive to the position of all the other atoms in the vicinity. He then asserts that a molecular assembler would thus have to control many atoms simultaneously in order to work, and would thus have to have many manipulator arms. This lead him to raise two objections to the concept of molecular assembler, which he calls the "fat fingers problem" and the "sticky fingers problem":

"Because the fingers of a manipulator arm must themselves be made out of atoms, they have a certain irreducible size. There just isn't enough room in the nanometer-size reaction region to accomodate all the fingers of all the manipulators necessary to have complete control of the chemistry.... the atoms of the manipulator hands will adhere to the atom that is being moved. So it will often be impossible to release this minscule building block in precisely the right spot. Both these problems are fundamental, and neither can be avoided. Self-replicating, mechanical nanobots are simply not possible in our world."

Smalley closed the article by returning to the analogy of chemistry as a dance of love, remarking that "you don't make a girl and a boy fall in love by pushing them together."

Drexler's response

Drexler responded by publishing a rebuttal later in 2001 through the Institute for Molecular Manufacturing, which was co-authored with others including Robert Freitas, J. Storrs Hall, and Ralph Merkle. The rebuttal's purpose was to refute both of Smalley's "fat fingers" and "sticky fingers" arguments, and to show that Smalley's conception of a molecular assembler was not consistent with Drexler's prior proposals.

Exchange of letters in Chemical & Engineering News

Response

The debate has been criticized for its tone. David Berube in Nano-Hype: The Truth Behind the Nanotechnology Buzz characterized it as "two people talking over each other... not conducive to reasonable rebuttal." Zyvex founder James von Ehr remarked that "Eric didn't do himself any favors by getting into a pissing match with a Nobel-prize winner." The New York Times called the debate "reminiscent of that old Saturday Night Live sketch... Dan Aykroyd and Jane Curtin tossing insults at each other while ostensibly debating a serious political issue."

Steven A. Edwards in The Nanotech Pioneers notes that the ambiguity of the specifications and even definition of a molecular assembler makes an evaluation of the argument difficult and minimizes its scientific implications. He remarks that "nowhere in it does Nanosystems contain a blueprint for a molecular assembler.... We are told, for instance, that a manipulator arm would involve 4,000,000 atoms, but we are not told which atoms, or how they would be put together." He concludes that "the debate over mechanisynthesis so far is huge to the participants, but mainly an entertaining academic diversion to most nanotechnologists."

References

1. ^ Edwards, Steven A. (2006). The Nanotech Pioneers: Where Are They Taking Us?. Weinheim: Wiley-VCH. pp. 15–21, 27.
2. Edwards, pp. 27, 64, 132, 184.
3. Smalley, Richard E. (2001). "Of Chemistry, Love and Nanobots". Scientific American. 285 (3): 76–7. PMID 11524973. {{cite journal}}: Unknown parameter |month= ignored (help)
4. Drexler, K. Eric; Forrest, David; Freitas, Robert A.; Hall, J. Storrs; Jacobstein, Neil; McKendree, Tom; Merkle, Ralph; Peterson, Christine (2001). "On Physics, Fundamentals, and Nanorobots: A Rebuttal to Smalley's Assertion that Self-Replicating Mechanical Nanorobots Are Simply Not Possible". Institute for Molecular Manufacturing. Retrieved 9 May 2010.
5. Berube, David (2006). Nano-Hype: The Truth Behind the Nanotechnology Buzz. Amherst, NY: Prometheus Books. p. 73.
6. ^ Edwards, p. 201.
7. Chang, Kenneth (9 December 2003). "Yes, They Can! No, They Can't: Charges Fly in Nanobot Debate". The New York Times. Retrieved 5 July 2011.

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