Critique of Nanotechnology

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I _ CRITIQUE OF HE WORD "nanotechnology" means very nanor different things to different people. While long-t NANOTECHNOLOGY: most would agree that Nanotechnology techni is technology performed on the scale of day's, nanometers - one nanometer being about the size A DEBATE IN FOUR of four zinc atoms laid side-by-side - that is where The b the agreement often ends. sembli byK. E PARTS To Howard Craighead, director of the National Nano- Manife fabrication Facility at Cornell University, Nanotech- asseml nology is a science that uses the chip-making tech- single . niques of the microelectronics revolution to produce made 1. Chemistry devices of increasingly smaller dimensions. chines robotic says it can't happen. To Rick L. Danheiser, a professor of chemistry at the struct ( Massachusetts BY SIMSON GARFINKEL Institute of Technology, Nanotech- vices a nology is a word that describes synthetic organic produce chemistry - a science whlic it woulc seeks to place atoms in precise a single and complex arrangements in order assemb) to accomplish exacting goals. Althoug To K. Eric Drexler, an author and single a, visiting scholar in the Computer thing la: Science department at Stanford lions of University, Nanotechnology de- gether c scribes a technology of the future You coul - a technology based upon self- the task replicating microscopic robots con- job with trolled by tiny mechanical com- diamond puters, capable of manipulating a time by matter atom by atom. from cart Who is right? Everybody and no- the surrc body, really, because "nanotech- rust and nology" isn't a scientific term. could res Nanotechnology is a mind set, an ance of th ideology, a way of solving big prob- ozone in lems by thinking small - think- They cou ing very small. eating up they coul One nanotechnology tool is molecular modeling software, such as SYBYL, shown My first exposure to Nanotechnol- seawater. here The program represents not only the 3D image of atoms but also their surrounding force fields. Images of atoms brought together wil but also theiral ogy was several years ago when I mate weal atoms, binding or repelling in a correspondingly "atomic" wa'y.Simulated eS ave e real was a student at MIT. A new stu- rip apart a chemistry such as this is now being used to design pharmacet iticals, in order dent activity was forming called There is cc to build drugs "rationally," atom by atom, much as nanotechi iology forecasts. the Nanotechnology Study Group, at the atot a band of individuals committed living thin to exploring the technology and implications of destroying Nanotechnologyisa new engineering skill which promises great "Nanotechnology." power by manipulating matter at the atom level (see WER #54, nanomachi p 8). To date, the debate over its consequences (solution or prob- The Study Group's handouts were drawings of atoms structural, lemS) have assumed its inevitability. Critiques of the proposed and some science - can it actually be done? - have been nonexistent in arranged into nanometer-sized gears and bearings, as the public discourse. The following critique of nanotechnology well as arrangements of atoms that were supposed to are almost doesn'taddress all the questions this technology brings up, but be memory circuits and logic building blocks for quire nearl' what a relief to have any technicalchallenge. Simson Garfinkel, nanometer-scale computers. But the people in the duce and rt a reporterforthe Christian Science Monitor, has a master'sdegree Study Group weren't things that in science journalism from Columbia andgraduated with a triple chemists and physicists: they major in chemistry political science, and history.of technology were computer scientists. The questions that the to do. at MIT: He starts off this four-part debate by challenging the Study Group was interested in exploring were not One of the underlying technical details this new power is based on. Eric "will these particular drawings of nanodevices work?" machines is Drexler, Visiting Scholarat Stanford University and a key vision- - it was taken for granted that if these didn't, others ary of nanotechnology, offers his rebuttal. Garfinkel responds, a red blood c and Drexler counters. Lastly, Steven Levy, author of Hackers, would - but rather, what would be the uses and im- circulatory reportson the first conference dedicated to the issues raisedhere. plications of such robots to medicine, science, in- posits When -Kevin Kelly dustry and warfare; what would happen if an army of doesn't belo: 104 WHOLE EARTHREVIEW SUMMER 1990

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neans very, nanorobots got out of control; and what would be their drills and shred the offending blockage. With a few ,ple. we-~: long-term impact on society. The people of the Nano- robot arms, the sub could even repair damage. Sort echn,. jy technology Study Group were the forerunners to to- of a nano-Fantastic Voyage, the concept of this sub has te scale of day's cult of Nanotechnology. appeared in prestigious newspapers like The New York it the size : Times and The Wall Street Journal, as well as mag- t is where The basic tool of the Nanotechnologist is the "assembler," according to Engines of Creation, the book azines such as Scientific American. The sub by K. Eric Drexler that reads like the Nanotechnologist represents the best of what Nanotechnology has to nal Nano- Manifesto. No larger than a few hundred atoms across, offer: the ability to make our lives better. '1anotech- assemblers would be constructed from gears that use The Cult of Nanotechnology paints a future in which king tech- single atoms for teeth and turn on frictionless pivots technology has grown unimaginably more powerful o produce made from single chemical bonds. These nanoma- than it is today. As a much bigger lever than any Is. chines would come equipped with a computer and a technology before it, they argue, it would do us well robotic arm, and have the remarkable ability to con- to think about the potential of the technology before stry at the struct "assemble") materials or molecule-sized de- the revolution happens: this is what they are doing. 4anotech- vices a single atom at a time. Assemblers would re- The problem with these people's ideas is that they ic organic produce by building exact copies of themselves - thus envision working with atoms the same way a model- :e which it would only be necessary to build n precise _ 1I_I ______t I I1 __ __ J I . 1_ . ts in order a single assembler, and this first A visualization of assembler would build the rest. goals. a nanomachine Although it would be slow for a swimming through athor and a capillary blood single assembler to construct any- vessel, chewing computer thing larger than a fly speck, bil- away a fat deposit, Stanford lions of assemblers working to- lower left. Glucose )logy de- gether could do almost anything. and oxygen in the he future You could set a fleet of them about blood power two tpon self- tiny screw propel- the task of covering your car's paint lers. The nanobot )bots con- job with a micron-thin coating of randomly wanders cal com- diamond, constructed an atom at through the capil- ipu'--` a time by assemblers using carbon laries, programmed to eat only fat. from carbon dioxide plucked from One can easily and no- the surrounding air: forget about imagine both the anotech- rust and car washes. Assemblers advantages and could restore the ecological bal- problems of such ic term. a device. d set, an ance of the planet by making more big prob- ozone in the upper atmosphere. - think- They could clean up oil spills by eating up the oil, or alternatively they could make oil from air and technol- seawater. In wartime, assemblers would be the ulti- maker might work with wooden sticks and styrofoam , when I mate weapon, programmed to be "'omnivores" and balls - breaking a bond here, moving an atom to the lew stu- rip apart attacking armies atom by atom. other side, and forming a new bond. It is that con- g called ceptual model which is at the heart of all the Nano- Group, There is certainly evidence that such manipulations at the atomic level are.possible. Every cell of every technologists' drawings of gears, motors and nanocom- nmitted living thing is constantly manufacturing, using and puter parts, as well as the very idea of the assembler's :ions of destroying tremendous numbers of relatively simple robot arm and the nanosub's drill. But atoms don't nanomachines called proteins. Some of them are work that way. ifatoms structural, some of them perform chemical reactions, ings, as and some of them transmit messages. But proteins "[Drexler] discusses these molecular systems as me- osed to are almost always single-purpose devices which re- chanical systems," says Robert . Silby, a professor of cks for quire nearly all of the machinery of the cell to pro- chemistry at MIT. "He bangs them and they go." in the duce and regulate them. No protein does all of the The problem is, Dr. Silby explains, "molecules are ts: they things that an assembler would supposedly be able not rigid - they vibrate, they have bending motions." hat the to do. Even cross-linked or interlocked networks of carbon ere not One of the most intriguing of the proposed nano- atoms exhibit these characteristics, Silby explains. work?" machines is the nanosub, a device a little smaller than "Therefore these will not act, mechanically, in the , other- I a red blood cell which could swim through a person's way he has written down. There is more to it than nd i: circulatory system in search of plaque or fatty de- he has said." ice, in- posits. Whenever the sub bumped into something that Take the example of the assembler's "'robot arm." irniy of I doesn't belong, it would switch on a powerful set of Such an arm could probably pick up a single atom,

27 GATEFIVE ROAD SAUSALITO,CA 94965 1 05 construe since lone atoms are very reactive and likely to stick breaking apart, there is no way that they could detect another anything that they come into contact with. Get- the reflected rays or collimate them into recognizable to than nat' ting the atom off the arm, on the other hand, would images, Perhaps the nanomachine will use electrons would h. require a lot of energy - quite possibly more energy or some other sub-atomic particle as a kind of atomic biologic, than the nanomachine would have available. "radar," but there seems no way that a nanomachine operate The robot arm might have a little more luck working could generate a predictable stream of such particles or interpret their reflections. At MIT, with groups of atoms, called molecular fragments. The says that Nature gets around the imaging problem by relying energy required to work with molecular fragments is nology h much lower than the energy needed to work with on molecular diffusion and randomness to bring mean th single atoms - this is the reason that proteins almost molecules to the places where chemical reactions can always work with molecular fragments. The only ways take place. As a protein comes into contact with a "I see so that a robot arm could hold a molecular fragment in target molecule, thermal noise and motion cause sibly exi: place would be by making a chemical bond to it or molecules to explore trillions of positions and orien- that Dre: by clamping the fragment in place with some sort of tations every second. But Drexler and other Nano- of a nan molecular cage. technologists maintain that nanomachines will not that he ( rely on diffusion because it is not look so gi An idealized van der precise enough for their purposes. it and di Waals bearing, a key Unfortunately, it is all that you Neverthe component in nanoma- have at the atomic level: even the chines. The molecular that the structure is similar to biological process of active trans- Students the "bearing" in cer- port which moves molecules Omni, tl tain bacteria, allowing across membranes relies upon its flagellum to spin diffusion and random motion to Indeed, (see illustration, p. 111). get the molecules into the mo- technolo Artificial nanobearings is "putti have not been built yet, lecular pumps. istry. Ch outer although organic ones The idea of a universal assembler ring are built by the most physics a I s ~ ~~overap primitive life forms. is somehow a very comforting hesitate Innerring one: a programmable machine, their bal I capable of manipulating atoms and carrying out reactions the What ups There are plenty of proteins that move molecular way that a blacksmith might repair a horseshoe with descripti( fragments around by using chemical bonds. But it is anvil and fire, is an easier image than proteins or in- by advoc always the case that the proteins can form these bonds organic catalysts carrying out complicated chemical descriptii only with one or two specific fragments. It is doubt- reactions by transferring electrons from atom to atom. on a fres] ful that an arm could be designed to bond with any And. indeed, in the beginning of his book, Drexler derstandi arbitrary piece of an arbitrary molecule. describes an assembler grasping "a large molecule analogy Molecular cages do occur in nature, but they tend (the work piece) while bringing a small molecule up is that cl into a b. to be bulky and unwieldy. While there are some pro- against it in just the right place. Like an enzyme, it teins'which hold molecules in their active sites with will then bond the molecules together." machine flaps constructed from chains of amino acids, such The idea of using a few well-crafted machines to make "That's active sites are always at the heart of the protein - billions, and then using a billion machines to solve organic s3 not on flexible arms which can easily be maneuvered the world's problems is really an appealing one. It is bolts tha

Light that has atomic-sized wavelengths is known as X-rays. However, even if the nanomachines could not generate enough energy to emit an X-ray without

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A tially as a could, etect constructions aren't possible: a lap-top computer is sketch that one might give an architect." II another good example of something more complicated ecog. Ale The most important developments in modern chem- than nature can build. But natural or not, assemblers se electrons istry, Danheiser says, is by "very, very serious chemists would have to exist in the same environment as the Idof atomic iZ who are actually involved in molecules that have com- biological molecules that they would be designed to nomachine plex function. This is rudimentary nanotechnology, operate on. ch particles although I don't think that they would call it that." At MIT, professor of chemistry Rick L. Danheiser says that just because some advocates of Nanotech- For example, the 1987 Nobel Prize in chemistry was i by relying awarded to three scientists who had done pioneering ;s to bring nology haven't had a training in chemistry doesn't mean that their ideas shouldn't be taken seriously. work in the field of molecular recognition - which actions can in a way can be thought of as "robot arms" that are tact with a "I see some anti-aromatic structures that can't pos- pre-programmed to "pick up" specific molecules 'tion cause sibly exist," Danheiser says, referring to the designs ; and orien- that Drexler has proposed for the "rod-based logic" Danheiser is also enchanted by the idea of a nano- ther Nano- of a nanocomputer. "It's unfortunate es will not I that he draws something that doesn't ise it is not look so good, because a lot of people see [r purposes. it and discredit the whole thing." 11 that you Nevertheless, Danheiser says, "I think 1:even the that they are doing a great service. :tive trans- Students in high school are reading molecules Omni, thinking 'that's really neat.'" lies upon motion to Indeed, what the advocates of Nano- o the mo- technology are doing, Danheiser says, is "putting a lot of glamor into chemistry. Chemistry suffers compared to assembler physics and biology.... That's why I omforting hesitate to do anything to puncture mache, their balloon." nga :tions te What upsets Danheiser is some of the shoe with descriptions of chemistry that are used :ins or in- by advocates of Nanotechnology - a chemical i descrintionn he says. that seems based g tunneling 1 to atom. on a freshman chemistry course's un- A scannin microscope no bigger than a high-school microscope pro- raits :, Drexler I of atoms. This image made by the Nanoscope Hshows iodine derstanding of the field. One common atoms absoorbed on the surface of a platinum crystal (notice the missing atom}. molecule analogy used by Drexler, for example, Being able to detect matter at the atom level is one step in learning to control lecule up is that chemists throw bolts and nuts the locatioin of atoms. izyme, it into a bag, shake it, and hope for a machine to come together. s to make a "That's not an accurate picture of what one does in submarine that swims around a person's circulatory ; to solve organic synthesis," says Danheiser. "We take nuts and system, looking for cancerous cells to destroy. But one. It is bolts that are cleverly machined so that they self- Danheiser describes the sub as a large molecule with ter scien- assemble in a specific manner." an artificial antibody on the front, grafted to a mole- ecursion James S. Nowick, who is completing a doctorate in cule of snake venom - a molecule which nature has hat refers given the capacity to cut up and destroy cells. ach that organic chemistry at MIT and plans to work in the field of uters, all molecular devices, puts it this way: "My main Such a machine, Danheiser stresses, wouldn't have tchunks criticism of Nanotechnology, or more in particular, to self-reproduce or even self-repair to be a medical Id of the of Drexler, is that he's coming forth as being sort of success. The machine could be made synthetically, ze.} Nan- a visionary without actually doing anything.... in a laboratory, and it could be "reprogrammed" by of these Whatever he is putting forth as science has to be chemically removing one antibody and replacing it inotech- tempered by the fact that we are dealing with some- with another one. body who is basically making )mputer predictions.... In my "Chemists are getting the short end of the stick," says ists and field, for instance, if you have a prediction of how Nowick. "The best thing that chemists can do is get ecricnce something will work you can't just go publish that. one or more spokespeople who are willing to beat the You really have to have scientific results. drum for the public, saying that 'this is chemistry, this '1 think that there are some problems and unreason- is exciting technology, you should be interested in it, comph- able aspects of some of the structures that Drexler has young people should pursue careers in it, and con- ture on drawn. However," Nowick says, "I see them essen- gressmen should provide more funding.' " l - at such

27 GATEFIVE ROAD SAUSALITO. CA 94965 107 The world's smallest operation Christmas card - plex, such only five square mi- The short 2. crometers, about a net effect billion times smaller Under special than usual - pro- 6. Will as duced by drilling Not direc conditions, holes four nanometers across in a manufact chemistry layer of aluminum thing so ( fluoride crystal. If fuels, ope can build stable it were possible to will be use write all the books and the nanostructures. in the Library of Congress at this particular BY K. ERIC DREXLER nano-scale, you to use gen could fit them onto be used to the head of a pin, an engine and still have room for all the volumes tion lines I HAVE BEEN ASKED to reply to in the rest of the Simson C .~es nZ..2... the preceding critique and have mai4JUr-nn 11UranIs 01 appliers (r the world. The holes done so in a hypertext style [to the more (below) are "drilled" the mess I refer to Simson Garfinkel's com- by dislocating atoms ments]; Whole Earth Review plans using a beam of Weapons to give Mr. Garfinkel another abi- electrons. Storing worry abo information by nano- by atom i lity that hypertext will provide technology may be more widely - the ability to re- its most probable suspects t spond to a response. first use. plications ized by th 1. What is nanotechnology? criticism. If they are true, then they have enormous devices. In Simson Garfinkel says that Howard Craighead defines consequences, and it is natural for people to become ing everyt nanotechnology as advanced microtechnology, while excited and for some to become starry-eyed. It would ing an im Rick L. Danheiser defines it as synthetic organic be an ad hominem fallacy, however, to judge the validi- everything chemistry. As this shows, these fields already have ty of technical concepts by emotional characteristics : 7. What names. So far as I can tell, it was I who introduced of the response they raise. Still, it is a good rule of atoms ant the term "nanotechnology" into general use, and as thumb to be especially skeptical of ideas that people Gears, mc Mr. Garfinkel's paragraph on my usage suggests, there seem to want to believe; accordingly, in my technical Simson G is no commonly accepted alternative name for the talks I urge my audiences "to be harshly critical of capabilities that "nanotechnology" is generally taken essentiall any ideas they hear labeled 'nanotechnology', starting ing operat If this technology is important, then it to describe. with my own." of industr: needs to be discussed and it needs a brief, unambi- 4. Can gears turn on frictionless pivots made from formation guous name. Sticking with the original meaning of single chemical bonds? tle reseml "nanotechnology" would be useful for this reason. All pivots (or bearings) have some sliding friction, or Note that (There is no perfectly clear line between synthetic drag, though they can be made to have a negligible ical terms chemistry and nanotechnology, but neither organic amount of static friction, or stickiness. Single is a stand is there a perfectly clear line between night and day; chemical bonds are too weak and elastic to use as bear- they are distinct, though one leads to the next.) 8. What a ings for the gears mentioned here, but there are other, Every ph, 2. Why are computer scientistsprevalent among those more adequate approaches based on sliding surfaces. nanomacd interested in nanotechnology? Like many of the points that follow, this was discussed Chemists and physicists are best placed to critique jects. Eve in my course at Stanford, "Nanotechnology and Ex- ' machines proposals in nanotechnology, but their orientation is ploratory Engineering." more quai that of scientists, not of engineers. The tend to focus 5. Will assemblers build devices a single atom at scale, the on what can be studied today, not on what can be built a time become ol tomorrow. Computer scientists (despite their name) In general, probably not, though I have sometimes issue in n are, in this sense, engineers. Further, they recognize used language that may suggest literal atom-by-atom tion this i the value of tiny, fast, controllable things, and they construction. A more accurate statement would be quantitati are habituated to technological revolution. something like "Assemblers will maneuver reactive logic syste 3. What are we to make of the excitement caused by chemical moeties to tenth-nanometer precision, ef- assembler the concept of nanotechnology? fecting a series of elementary chemical reactions, each distributk I believe Marx once said, "I am not a Marxist." I may of which adds one or several atoms to a workpiece, fields, tho be forced to echo this remark. The basic concepts of giving precise control of the resulting molecular struc- suits were nanotechnology are technical and open to technical ture." And even this is a simplification, since a typical departmei

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:Id's :st operation will often do something a bit more com- 9. What about problems with picking up andplacing tas car - plex, such as adding three atoms while removing one. lone atoms? t square mi- The shorter description gives a clear picture of the See (5). rs, about a net effect. limes smaller 10. Need an arm bond with any arbitrarypiece of an lal - pro- 6. Will assemblers do all these things? arbitrarymolecule? Vdrilling Not directly. Assemblers will be general-purpose Assembler arms will wield a variety of tools, each ur nano- with a standard "handle" fitting a standard "hand"; icross in a manufacturing machines, able to make almost any- aluminum thing so long as they are given the right raw materials, the tools themselves will be specialized. Further, crystal. If fuels, operating conditions, and instructions. They only a limited range of tools would be needed to build ,ossible to will be used to make many special-purpose machines, a wide variety of products, since even a complex pro- i the books and the latter will do most of the work. To make a duct can be built through a complex series of simple ibrary of s at this particular product in quantity, it will make no sense operations. All this is familiar from macroscopic lie, you to use general-purpose assemblers; these will instead manufacturing technology. : them onto be used to build a special-purpose production line, like 11. Will nanomachines use x-ray or electron-beam I of a pin, an engine fabrication line in Detroit. These produc- have room "radar" to spot molecules? te volumes tion lines will then be used to turn out devices like Surely not, for reasons well-stated here (I have not seen st of the Simson Garfinkel's hypothetical diamond-coating- this proposed elsewhere). Further, freely moving mol- braries of appliers (perhaps formulated into a rub-on paste?), or ecules would elude grabbing even if they could be d. The holes the more desperately needed devices able to clean up seen; assembler arms would simply be too slow. In- are "drilled" the mess made by 20th-century industrial technology. :ating atoms dustrial robots typically pick pre-positioned, pre- seam of Weapons are among the potential products we need to oriented parts off something like a conveyor belt, s. Storing worry about, but ripping attacking armies apart atom rather than rummaging around in a bin - and this tion by nano- despite the greater ease of vision on a macroscopic ,gy may be by atom is rather too crude and too dramatic; one probable suspects that the military mind will find other ap- scale. I expect that assemblers will work in a similar plications for a manufacturing technology character- fashion. ized by the construction of precise and sophisticated 12. Will nanomachines rely on diffusion? enormous devices. In general, having an image of assemblers do- There is a distinction to be drawn between relying on to bo'ne ing everything in the future would be a bit like hav- diffusion somewhere, and relying on it everywhere. -d. It .ld ing an image of lathes and milling machines doing Assemblers will enable precise construction of large, ;e the validi- everything today. complex molecular systems because they (i.e., their Lracteristics 7. What does nanotechnology assume about how positioning arms) will be able to direct chemical re- ;ood rule of atoms and molecules work? actions with a specificity and reliability that cannot that people Gears, be achieved when molecules are free to bump together iy technical motors, mechanical nanocomputer parts, and Simson Garfinkel's proposed drill would work in an in all possible positions and orientations. Thus, they I critical of essentially mechanical fashion, as would the avoid diffusion when moving molecules to the site of gy', starting positioning operations of assembler arms (resembling those reaction. General-purpose assemblers are expected to of industrial robot arms). The actual chemical trans- pluck tools incorporating reactive molecules off con- made from formations effected by assemblers, however, have lit- veyor belts which have been loaded with activated tle resemblance to familiar mechanical operations. tools by special-purpose systems of somewhat en- friction, or Note that describing molecular motions in mechan- zyme-like machinery, which in turn have gotten their i negligible ical terms (e.g., in the field of molecular mechanics) raw materials from the surrounding solution. This ess. Single is a standard part of chemistry. earliest step will involve the transfer of molecules - use as bear- by diffusion - from that solution to selective binding 8. What about elasticity and vibrations? re are other, sites like those familiar in proteins and supramole- Every physical object is a collection of atoms; ng surfaces. cular chemistry. nanomachines will simply be very small physical ob- is discussed jects. Everything vibrates, everything bends, and 13. How complicated are assemblers? )gy and Ex- machines work regardless; the differences here are Assemblers and nanocomputers will be roughly as more quantitative than qualitative. On a very small complex as industrial robots and microcomputers, 'le atom at scale, the vibrations associated with heat itself because they will contain similar numbers of parts become of tremendous importance, and are a crucial performing similar functions. All these devices, sometimes issue in nanomachine design and operation. I men- however, will be far less complex (and adaptable) than im-by-atom tion this issue in Engines of Creation, and have done living organisms; they will have broader capabilities .t would be quantitative analyses of thermal vibrations in both in some respects, but not in all. ver reactive logic systems for mechanical nanocomputers and in 14. Can these anti-aromaticstructures exist? ecisio-ef- assembler arms. There is a lag in publication and For quantum-mechanical reasons, some molecules ction .h distribution of information in new, interdisciplinary that can be drawn as rings with alternating double workpiece, fields, though, so it would be surprising if these re- and single bonds are especially stable (like the six- :cular struc- sults were universally known in the MIT chemistry membered benzene ring) and others are especially ice a typical department. unstable (like the four-membered cyclobutadiene

27 GATEFIVE ROAD SAUSALITO.CA 94965 1 09 ring). One of my nanomechanical designs contains a Indeed, in the 1930s members of the British Inter- ring resembling the latter; it has the advantage of hav- planetary Society performed feasibility studies which a shade ing a useful shape for the purpose. Is its "instabili- argued that one could fly to the Moon with rockets. I believe ty" a problem' With care, feasibility studies can be done today in the human r yvinevit Chemists regard chemicals as unstable when for ex- field of nanotechnology. The required intellectual discipline includes strict avoidance of areas of scien- understa ample) they spontaneously dissociate, or rearrange, we can or react with themselves at a high rate, or when they tific uncertainty (or pursuit of designs which are policies. readily react with a variety of other molecules. This robust despite a given range of uncertainty); it is thus final process is not intrinsic to the molecule, but closer to engineering than it is to science. To scien- Nanotec results from the presence of other reactive molecules. tists, engaged in learning new facts about nature, talk ufacturir In a different environment, the molecule will be of future knowledge is speculative and often pointless. possible stable. Chemists ordinarily work with molecules in To engineers, engaged in building new devices, talk with it' solution, and in vast numbers; these molecules are of future possibilities grounded in establishedscience the biosl free to encounter others of the same kind, so any re- need not be speculative and is often essential. garding actions that occur will be unavoidable. This is a The above is a fragmentary sketch of some issues in which nr stronger kind of instability, typically dealt with by stu- the methodology of exploratory engineering. A chap- skepticis dying molecules under low-density, near-vacuum con- ter-length exposition is available (see the closing note ditions, or in solid matrices of noble gases at tem- for further information). peratures near absolute zero. If one can indeed understand something about future Under the latter conditions, cyclobutadiene exists, but technologies, should we ask that everyone refrain from it begins reacting with itself on even slight warming doing so (or at least from publishing the results) before un. (to 25 degrees Kelvin). In a nanomachine, of course, these technologies are demonstrated? To do so would the molecules do not wander freely; they encounter only be to request that society turn a blind eye to a signifi- certain other structures in certain orientations. Under cant scrap of knowledge regarding our future. I believe these conditions, the cyclobutadiene ring can indeed that exploratory engineering deserves a genuinely tiny be stable (as it is at room temperature when surround- fraction of society's technical effort, and that its pro- ed by bulky, branched side-chains). A call to Rick L. ducts, when they seem interesting, deserve rigorous A BIT O Danheiser confirmed that he shares this view of sta- criticism - or partial, carefully hedged approval, In Janual bility and its application to the case at hand; I had when merited - from those with competence in a fomia, ta run these structures by another organic chemist for relevant field. lity of m; criticism before publishing them. Only instability in 17. Are we doing nanotechnology today? "I don't the sense of a molecule falling apart or rearranging The developments and goals cited here are relevant, referring spontaneously can be used to criticize a structure out and show how short-term objectives are leading toward I': ler. It wa, of context and even then a suitable molecular envi- steadily more sophisticated molecular devices. In my be places ronment can create exceptions, left as an exercise for work I have focused on long-term developments, and simply d the nanotechnologically inclined chemist). have described devices that no one 'would consider try- chemistr 15. What about these freshman-chemistry-course ing to build today (because we lack the tools) and that i as small, analogies? no one is likely to build tomorrow (because we will sarily ha, They are intended to inform readers with diverse then have better designs). Still, even the crude Brand im backgrounds, sometimes lacking even freshman nanotechnology I am able to describe and defend objection chemistry itself. They are useful in the same way that would have capabilities far beyond what has been showing Danheiser's reference to "machined" molecules is achieved today. We are speaking of the difference be- whose op useful - as metaphors to convey a qualitative under- tween a mousetrap on the floor and a gripper on an I saying th. standing of some aspect of the subject matter, such industrial robot arm backed up by a computer. Others rel as the ability of synthetic organic chemists to make In closing . . . what the a wide range of moderately complex structures with I thank Simson Garfinkel for a stimulating critique scientific precision. (For perspective: in chemical synthesis, a of my work; it has provided an occasion to explain hundred-atom structure is considered large and com- Making p several points previously made only in teaching or in whose tra plex but an assembler arm will likely have on the conference proceedings. A general observation seems is bound t order of a million). in order, however, given a natural and widespread mulating 16. Should one talk about what has not been misunderstanding of my view and the it-would-be- realize th demonstrated? nice-if tone of his essay: I have not advocated of possibi James S. Nowick is correct that predictions are not nanotechnology, I have advocated understanding it. and not t publishable in many fields of science. However, nano- Reporters, hearing me describe a technology that can was born. technology is not a branch of science (as I have taken accomplish many long-sought goals, often assume I pains to point out in Engines of Creation); it is an must think that it is an unalloyed blessing, or at least The heart engineering discipline based on established science. a good thing - even when I emphasize its great poten- Drexler is Engineering projects are often discussed and written tial for abuse (Engines of Creation has a chapter titled Drexler b about before they are undertaken. "Engines of Destruction"). My position seems just should no nology" a I I 0 WHOLE EARTHREVIEW SUMMER1990

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:ish JI-. lies w. - a shade too subtle to fit a simple, stereotyped story: But Nanotechnology is not like biotechnology or mi- h rockets. I believe that in our diverse, competitive world, basic crotechnology: Both biotechnology and microtechnol- day in the human motivations make nanotechnology effective- ogy exist: there are laboratories where work is done, tellectual ly inevitable, and that, in light of this, we need to journals where results are published, and physical s of scien- understand its great potential for good and ill so that devices which put these technologies to work. vhich are 11' we can formulate and act in accord with effective Nanotechnology has none of these physical trappings; ; it is thus policies. it is not yet an "engineering discipline," as Drexler To scien- Nanotechnoloy will, I believe, be the dominant man- maintains 1161, because there is nothing that is be- iture, talk ufacturing technology of the coming century, making ing engineered in any conventional sense. This is why pointless. possible a host of amazing products. What we build many scientists think Nanotechnology is science fic- ,ices, talk with it will make a vast difference to human life, tion. It isn't that "there is a lag in publication and ;d science the biosphere, and the future of the world. Ideas re- distribution of information in new, interdisciplinary itial. garding nanotechnology need to be taken seriously, fields," as Drexler contends [8]. Indeed, an astounding issues in which means evaluating them with proper care and number of people are familiar with his work. g.A chap- skepticism. L[ Perhaps the word "nanotechnology" (the uncapitaliz- )sing note ed version) wasn't in wide use when Drexler started 3. out, but it is now, and it is generally regarded by those )ut future Molecules are too in the microelectronic and microfabrication corn- (rain from Itsl before unstable to be controlled The propeller: a filament so would the way Nanotechnology a signifi- .I believe needs. inely tiny by Garfinkel at its pro- rigorous A BIT OF BACKGROUND . . . appr-- In January, I found myself in a lecture room in Cali- ence fornia, talking with Stewart Brand about the possibility of machines no larger than a wavelength of light. I "I don't believe in Nanotechnology," I finally said, relevant, referring to the lectures and writings of K. Eric Drex- I=o ng toward I ler. It wasn't that I didn't believe that atoms couldn't :es. In my be placed into precise arrangements, I explained. I rO ents, and simply didn't believe that the laws of physics and z Each propeller-like filament that propels a bacterium is Isider try- 4 chemistry would ever allow the creation of machines I and that as small, yet as complex, as Drexler's would neces- driven by a motor under the bacterium's cell wall. The sarily have to be. filament's drive (transferred through a 90-degree elbow e we will "gear") is an electric motor turned by a chemically induced ie crude Brand invited me to write an article explaining my flow of protons. A similar design can be used to move d defend objections, so when I returned to Cambridge I started nanomachines. has been showing Drexler's papers to chemists and physicists rence be- whose opinions I respected. Many of them laughed, munities to mean lithography at the nanometer scale. )er on an saying that Drexler's predictions were "'impossible." "Nanotechnology" and "'nanotechnology" therefore uter. Others refused to comment, hoping to stay away from mean different things to different people, and this is what they saw as science fiction masquerading as my reason for insisting on the capital-N. Names are ;critique scientific controversy. important, because they are the place-markers that we use for ideas. explain Making predictions is a tricky art, and Mr. Drexler, iing or in whose training is in computer science, not chemistry, )n seems Science fiction - or, more appropriately, speculative is bound to misplace a bond here or there. But in for- fiction - serves many useful purposes. Drexler's despread mulating my disagreements wth Drexler, I came to iould-be- predictions force one to think about the problems realize that many of his writings contain the seeds caused by chemistry, biotechnology and physics, and dvocated of possibility, if some of his words were translated nding it. how to solve them. But to talk about Nanotechnology and not taken at face value, and so my first article in such certain terms as Drexler does, always writing that can was born. assunr-' about what it "'will do," leaves a bad taste in the I t . The heart of my continued disagreement with Mr. mouths of many scientists. at poten- Drexler is summed up by the matter of capitalization: ter titled Drexler believes that the word "Nanotechnology" It isn't that chemists and physicists "tend to focus ems just should not be capitalized, just as the words "biotech- on what can be studied today, not on what can be built nology" and "'microtechnology" are not capitalized. tomorrow," 2] as Drexler asserts. Scientists simply

27 GATEFIVE ROAD SAUSALITO.CA 94965 1 1 1 tend to focus on what they think is allowed under the are many guidelines that chemists follow to assess laws of chemistry and physics. Whether Drexler's stability. In general, four-member rings, such as: Nanomachines follows these laws remains to be seen. C --- N C C In Drexler's world of Nanotechnology, atoms do ex- actly what he wants them to do. Drcxler's atomic or I I bonds, for example, are extremely rigid - they have C - C to be, so that his atom-sized gears will turn instead are intrinsically unstable because they place carbon of simply having their teeth bent. Likewise, physical bonds at 90-degree angles, instead of the preferred effects like diffusion seem to turn on or off as needs tetrahedral angle of 109.5 degrees. Yet it is these in- are dictated by Drexler's designs. Small reactive mol- stable structures that appear in Drexler's proposed ecules, for example, never, ever slip into the Nano- "Probe knob structure" and "Gate knob structure," machines and gum up the works. "In a nanomachine, which are the basis of his mechanical Nanocompu- of course, molecules do not wander freely; they en- ter. If these structures begin to disintegrate at 25 counter only certain other structures in certain orien- degrees Kelvin l141, how will they last inside a Nano- tations," Drexler writes 1141. How does a Nanoma- computer? Even if the computer were supercooled, the chine protect itself? How does it repair itself when smallest amount of mechanical energy (perhaps a it breaks? result of the computer's operation?) would be enough It all goes back to the very mechanistic view of atoms to set them off. and bonds which most of Drexler's work is based on. In my original article, I tried to stay clear from ar- While "describing molecular motions in mechanical guments about whether this or that arrangement of .t terms is a standard part of chemistry," [71 chemists atoms would be stable or not, because such arguments , do not think about chemical reactions in such terms. cannot be productive. It is impossible to prove that The most important thing in chemistry is the move- something cannot exist. If by some chance I should ment of electronic charge, not the movement of convince Drexler that he made a mistake, all he would atoms. Once electrons move, atoms rearrange them- have to do is come up with some alternative arrange- t selves automatically, because at the atomic level elec- ment of atoms and say, "Well, how about this one?" trostatic force is thousands of times stronger than I agree with Drexler that he has "described devices mechanical force. Nevertheless, Drexler continues to 'd.v write about atoms if they were so many wooden balls, that no one would consider trying to build today pegs and springs. (because we lack the tools) and that no one is likely to build tomorrow (because we will then have better To say, as Drexler does, that the arms of Assembler designs)." [17 1 think that he should include this need not be able to bind to arbitrary molecules - in- statement as a footnote to every molecular structure stead, they wield tools that have this ability 10], is he publishes. to restate the question, not answer it. How will a Certainly we should talk and think about things that "limited range of tools" be used to "build a wide variety of products?" have not been demonstrated; such discourse is at the heart of all future discoveries. But if we claim that i' "Macroscopic manufacturing technology," it turns such discussions are scientific, then it is important out, is a very bad model for how to build things at to stay within the laws of established science. I have the molecular level. I can lift a quarter from a table read philosophy and scholarly discussion about the top with a tweezer, a pair of pliers, or even with two possibility and implications of time travel, but I do chopsticks. But biology teaches us that nearly every not consider it a serious possibility, nor would I write molecular fragment must be manipulated by a uni- an article on all the things that we could do "when que tool, a special-purpose protein designed specifi- time travel is a reality." cally for the task. Other proteins simply don't work: I wouldn't say that "since time travel is an inter- they either can't pick up the particular molecular disciplinary study, it is understandable that many peo- fragments because the fragments don't fit properly ple are not familiar with the means by which it will and slip out due to vibrations), or they can't let go be achieved." Drexler has made many such statements (because the fragments irreversibly bind to the tools.) about Nanotechnology, angering and alienating many Likewise, if Assemblers do not need radar or vision scientists. because they pick "pre-positioned, pre-oriented parts In closing, as a science writer whose first scientific off something like a conveyor belt," 1111 the next training was in chemistry, I can only hope that Drex- logical questions to ask is "how do the parts get on ler's graphic descriptions of his world of Nanotech- the conveyor belt in the first place?" and "what pre- nology stimulate more popular interest in the chem- positioned and pre-oriented them?" ical and biological sciences. I simply fear that he has I was quite surprised that Drexler defended his pub- been too cavalier in many of his descriptions, and that lished structures as stable. Although it is impossible scientific possibility has often been pushed aside for to know with certainty whether or not a proposed sensationalism. molecule is stable without actually making it, there To say flat out that "I don't believe in Nanotechnol-

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w to mAess ogy" is probably a misnomer. I certainly believe that tounding number of people," (etc.) as being critical such our ability to control the placement and arrangement of my work, but who are they, and what are their of atoms will only get better as time goes on. A cen- substantive criticisms? In the case of Prof. Danheiser I tury from now, a student of history may discover Drex- we were given a name and a direct, substantive quote; .2 ler's articles and, with some amusement, note the after a few minutes of discussion with him, the dif- similarities between what Drexler predicted and what ficulty evaporated. I have yet to encounter a major came to pass, just as I might read Charles Babbage's technical criticism of the core concepts of nanotech- ace carbon plans for a computer based upon a steam engine. But nology that does not evaporate once it is examined. e preferred I think that the technology that future manufacturers There seems to be a lot of smoke in the air, but no is these in- use to arrange the placement of atoms will look a lot fire - perhaps the haze is fog? s proposed more like conventional chemistry and biology. And structure," while this might be a "Nanotechnology" of a sort, A few notes: My training is not in computer science, mocompu- it is a far cry from self-reproducing, self-repairing Nan- as Mr. Garfinkel states, but in interdisciplinary sci- ,rate at 25 omachines driven by tiny mechanical computers. a ence and engineering. Molecular diffusion is indeed de a Nano- cooled, the (perhaps a 4...... y.....:...... *...... ".%.. %...... be enough Natural materials ...... 7i==~~, \/i7_ ir from ar- prove that nanostructures C-C= C-C= C- G -C, - -C- _ gement of can be built. arguments .ari prove that by Drexler e I should 1 he would I AM SOMEWHAT disappointed by One part of a nanotechnology computing machine is suggested by this re arrange- the tone of Mr. Garfinkel's re- structure devilsed by Eric Drexler. It is an "alignment knob" which slides this one?" sponse to my response; much of it back and fortlhin a slot and aligns the arrays of mechanical components -d devices shifts away nic assemblages) so that they can "calculate" in the manner from his original, val- (all small ator adding machines. lild 'v uable focus on technical criticism e is . ,y to a focus on style, words, and feel- ave better I ings. These are important in their place, but are controllable, being rapid in gases and liquids and ef- :lude this scarcely scientific or professional in the context of a fectively blocked by suitable solid walls. I trust this structure technical debate. Some of his criticisms amount to explains why I assume that it occurs in some places a request that I repeat certain elementary points and not in others. Molecular mechanics is indeed not kings that _Z111 throughout my writings. This might inhibit misun- the whole story of chemistry - it gives a decent e is at the derstandings, but it would also inhibit communica- description of molecular vibrations and rotations, but laim that f tion of anything new. If the term "nanotechnology" not of chemical reactions. Single-atom gear teeth will mportant were widely used in the U.S. in the manner that Mr. indeed bend under load (why would anyone assume ,ce. I have 1 Garfinkel suggests, I would expect a reasonable frac- that I think otherwise?), but they will also turn the about the 4; tion of technical papers and news articles to use it gear, given any sort of reasonable bearing. How will , but I do I that way; they don't. a limited range of tools build a wide variety of prod- ild I write His strongest criticism, if true, would be my propos- ucts? In much the same way that they do in synthetic lo "when ing unstable four-membered rings and thus revealing organic chemistry, in living organisms, in home a dramatic ignorance of chemistry. But these rings do workshops, and in flexible manufacturing plants; ask an inter- not "disintegrate" at 25 degrees Kelvin, they dimerize, J. Baldwin. Time travel is a straw man, and no friend nany peo- and this requires that two molecules encounter one of mine. ch it will another in an orientation which would be prevented atements by mechanical constraints in the nanocomputer. Regarding Mr. Garfinkel's last two sentences, amen! ing many Again, and more clearly: I have discussed this matter But I have been at some pains to distinguish my with Prof. Danheiser, whom Mr. Garfinkel quotes designs from "predictions"; they are intended only ;cientsfic against me, and he agrees with my view of the mat- to show that devices having certain capabilities are iat Drex- ter. Indeed, he stated that he had never heard me say physically possible, so that we can try to prepare for anotech- anything that was inconsistent with today's chemical their emergence in the real world. I am glad that this ae chem- knowledge, though he noted that he had heard some intertwined collection of arguments and design con- at he has serious distortions at second hand. cepts has persuaded Mr. Garfinkel that these prospects anc" Mr. Garfinkel speaks of "many scientists," "an as- are real. asiu. , Readers in the U.S. can obtain copies of the essay "Exploratory Engineering," together with a Britannica reprint on nanotechnology, by sending a stamped, self-addressed large envelope with $1.25 postage to the Foresight Institute, P. 0. Box ,technol- 61058, Palo Alto, CA 94306. Outside the U.S., send $4 for airmail delivery.

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