Six challenges for molecular nanotechnology

To the outsider, the debate about whether Drexler’s vision of radical nanotechnology – molecular manufacturing or molecular nanotechnology (MNT) – is feasible or not can look a bit sterile. Many in the anti- camp take the view that the Drexler proposals are so obviously flawed that it’s not really worth spending any time making serious arguments against them, while on the pro- side the reply to any criticism is often “it’s all been worked out in Nanosystems, in which no errors have been found”. I think the recent debate we had at Nottingham did begin to move onto real issues. I can’t help feeling, though, that the time has come to move on from debating positions.

With this in mind, here are six areas in which I think the proposals of molecular nanotechnology are vulnerable. Trying to be constructive, I’ve tried, as far as possible, to formulate the issues as concrete research questions that could begin to be addressed now. Ideally, we would be seeing experimental work – this field has been dominated by simulation for too long. But theory and simulation does have its place; one has to recognise the limitations of the simulation methods being used and to validate the simulations against reality whenever possible. A couple of recent developments from the pro-MNT camp are encouraging – the Drexler/Allis paper (PDF) used state of the art quantum chemistry methods to design a “tool-tip” for mechanosynthesis, while the Nanorex program should make it much more convenient to do large scale molecular dynamics simulations of complex machine systems. What’s needed now is a systematic and scientific use of these and other methods, moderated by frequent reality checks, to answer some well-posed questions. Here are my suggestions for some of those questions.

1. Stability of nanoclusters and surface reconstruction.
The Problem. The “machine parts” of molecular nanotechnology – the cogs and gears so familiar from MNT illustrations – are essentially molecular clusters with odd and special shapes. They have been designed using molecular modelling software, which works on the principle that if valencies are satisfied and bonds aren’t distorted too much from their normal values then the structures formed will be chemically stable. But this is an assumption – and two features of MNT machine parts make this assumption questionable. These structures typically are envisaged as having substantially strained bonds. And, almost by definition, they have a lot of surface. We know from extensive experimental work in surface science that the stable structure of clean surfaces is very rarely what you would predict on the basis of simple molecular modelling – they “reconstruct”. One highly relevant finding is that the stable form of some small diamond clusters actually have surfaces coated with graphite-like carbon (see here, for example). There are two linked questions here. We need to know what is the stable structure at equilibrium – that is the structure with the overall lowest free energy. It may be possible to make structures that are metastable – that is, structures that are not at equilibrium, but which have a low enough probability of transforming to the stable state that they are usable for practical purposes. To assess whether these structures will be useful or not, we need to be able to estimate two things – the energy barrier that has to be surmounted, and how much energy is available in the system to push it over that barrier. The second of these factors is going to be closely related to challenge 3.

Research needed. Firstly, we need proper calculations, using quantum chemistry techniques (e.g. density functional theory) of the chemical stability of some target machine parts. Subsequently it would be worth doing molecular dynamics calculations with potentials that allow chemical reactions to probe the kinetic stability of metastable structures.

2. Thermal noise, Brownian motion and tolerance.
The Problem. The mechanical engineering paradigm that underlies MNT depends on close dimensional tolerances. But at the nanoscale, at room temperature, Brownian motion and thermal noise mean that parts are constantly flexing and fluctuating in size, making the effective “thermal tolerance” much worse than the mechanical tolerances that we rely on in macroscopic engineering. Clearly one answer is to use very stiff materials like diamond, but even diamond may not be stiff enough. The Nanorex simulations show this “wobbliness” very clearly. It should be remembered that in these simulations, the software nails down the structures at fixed points, but in reality the supports and mountings for the moving parts will all be just as wobbly. Will it be possible to engineer complex mechanisms in the face of this lack of dimensional tolerance?

Research needed. Drexler’s “Nanosystems” correctly lays out the framework for calculating the effects of thermal noise, but the only application to an engineering design of these calculations is a calculation of positional uncertainty at the tip of a molecular positioner. This shows that the positional uncertainty can be made to be less than an atomic diameter – this is clearly a necessary condition for such devices to work, but its not obvious that it is a sufficient one. What is needed to clarify this issue are molecular dynamics simulations carried out at finite temperatures of machines of some degree of complexity, in which both the mechanism itself and its mounting are subject to thermal noise.

3. Friction and energy dissipation.
The Problem. As mechanisms get smaller, the relative amount of interfacial area becomes much larger and surface forces become stronger. As people attempt to shrink micro-electromechanical systems (MEMS) towards the nanoscale the combination of friction and irreversible sticking (called in the field “stiction” ) causes many devices to fail. It’s an article of faith of MNT supporters that these problems won’t be met in MNT systems, because of the atomic perfection of the surfaces and the rigorous exclusion of foreign molecular species from the inner workings of MNT devices (the “eutactic environment” – but see challenge 5 below). Its certainly true that the friction of clean diamond surfaces is likely to be very low by macroscopic standards (the special frictional properties of diamond were already understood by David Tabor), particularly if the two sliding surfaces aren’t crystallographically related. However, in cases where direct comparisons can be made between the estimates of sliding friction in Nanosystems and the results of molecular dynamics simulations (e.g. Harrison et al., Physical Review B46 p 9700 (1992)) the Nanosystems estimates turn out to be much too low. MNT systems will have very large internal areas, and as they are envisaged as operating at very high power densities; thus even rather low values of friction may in practise compromise the operations of the devices by generating high levels of local heating which in turn will make any chemical stability issues (see challenge 1) much more serious.

Given that the machine parts of MNT are envisaged as being so small, and the contacting area of these parts is so large with respect to their volumes, it’s perhaps questionable how useful friction is as a concept at all. What we are talking about is the leakage of energy from the driving modes of the machines into the random, higher frequency vibrational modes that constitute heat. This mode coupling will always occur whenever the chemical bonds are stretched beyond the range over which they are well approximated by a harmonic potential (i.e. they obey Hooke’s law). At least one of the Nanorex simulations shows this leakage of energy into vibrational modes rather clearly.

Research needed. The field of nanoscale friction has moved forward greatly in the last ten years (a good accessible review by Jacqueline Krim can be found here), and an immediate priority should be to explore the implications to MNT of this new body of existing experimental and simulation work. Further insight into the scale of the problem and any design constraints it would lead to can then be obtained by quantitative molecular dynamic simulations of simple, driven nano-mechanical systems.

4. Design for a motor.
The Problem It’s obvious, on the one hand, that MNT needs some kind of power source to work. On the other hand, MNT supporters often point to the very high power densities that it will be possible to achieve in MNT systems. The basis of their confidence is a design for an electrostatic motor in Drexler’s “Nanosystems”, together with some estimates of its performance. The design is very ingenious in concept – it essentially works on the principle of a Van der Graaf generator worked backwards. The problem is that only the broad outline of the design is given in Nanosystems, and when one thinks through in detail how it might be built more and more difficulties emerge. The design relies on the induction of charge by making successive electrical contact between materials of different work-functions. The materials to be used need to be specified and the chemical stability of the resulting structures need to be tested as in challenge 1. This is a potentially tricky problem, as the use of any kind of metal is likely to raise serious surface stability issues. The design also specifies that electrical contact is made by electron tunneling rather than direct physical contact. This is probably essential in order to avoid immediate failure due to the adhesion of contacting surfaces (this would certainly happen with a metallic contact), but in turn, because of the exponential dependence of tunnelling current with separation) it calls for exquisite precision in positioning, which brings us back to the problems of tolerance in the face of thermal noise discussed in challenge 2.

Research needed. The electrostatic motor design needs to be worked up to atomistic level of detail and tested.

5. The eutactic environment and the feed-through problem.
The Problem It is envisaged that the operations of MNT will take place in a completely controlled environment sealed from the outside world – the so-called “eutatic” environment. There are good reasons for this: the presence of uncontrolled, foreign chemical species will almost certainly lead to molecular adsorption on any exposed surfaces followed by uncontrolled mechanochemistry leading to irreversible chemical damage to the mechanisms. MNT will need an extreme ultra-high vacuum to work. (It’s worth noting, though, that even in the absence of the random collisions of gas molecules Brownian motion – in the sense of thermal noise – is still present at finite temperatures). But, to be useful, MNT devices will need to interact with the outside world. A medical MNT device will need to exist in bodily fluids – amongst the most heterogenous media its possible to imagine – and a MNT manufacturing device will need to take in raw materials from the environment and deliver the product. In pretty much any application of MNT molecules will need to be exchanged with the surroundings. As anyone who’s tried to do an experiment in a vacuum system knows, it’s the interfaces between the vacuum system and the outside world – the feed-throughs – that cause all the problems. Nanosystems includes a design for a “molecular mill” to admit selected molecules into the eutactic environment, but again it is at the level of a rough sketch. The main argument about the feasibility of such selective pumps and valves is the existence of membrane pumps in biology. But I would argue that these devices are typical examples of “soft machines” that only work because they are flexible. Moreover, though a calcium pump is fairly effective at discriminating between calcium ions and sodium ions, its operation is statistical – its selectivity doesn’t need to be anything like 100%. To maintain a eutactic environment common small molecules like water and oxygen will need to be excluded with very high efficiency.

Research needed. Molecular level design of (for example) a selective valve or pump based on rigid materials that admits a chosen molecule while excluding (say) oxygen and water with 100% efficiency.

6. Implementation path.
The Problem The all-important practical question is, of course, how do we get from our technological capabilities today to the capabilities needed to implement MNT. Here there is a difference of opinion within the pro-MNT camp, with two quite different approaches being proposed. Robert Freitas believes that the best approach is to develop the current approaches of direct molecular manipulation using scanning probe microscopes to the point at which one is able to achieve a true mechanosynthetic step. This is interesting science in its own right, but some idea of the formidable difficulties involved can be found by reading Philip Moriarty’s critique of a specific proposal by Robert Freitas, and the subsequent correspondence with Chris Phoenix. Drexler himself prefers the idea of developing a biomimetic soft nanotechnology very much along the lines of what I describe in Soft Machines, and then making a transition from such a soft, wet system to a diamond based “hard” nanotechnology. This involves a transition between two completely incompatible environments, and two incompatible design philosophies, and I simply don’t see how it could happen. Without a concrete proposal it’s difficult to judge feasibility or otherwise.

Research needed. Engage with scanning probe microscopists to overcome the formidable experimental problems in the way of direct mechanosynthesis. Develop a concrete proposal for how one might make the transition between a functional, biomimetic “soft nanotechnology” system and hard MNT.

49 thoughts on “Six challenges for molecular nanotechnology”

  1. Wow!

    What you leave out is of course the number of nobel prizes!

    Good Luck and Merry Christmas

    An amateur mathematician

  2. So the behaviour of diamonds limits molecule machine parts to around 50000 carbon atoms. And best-case scenario is that chunky molecules are much more likely to be stable than exotic configuarions?

  3. All the best to you too, Zelah.

    Brian, I’m not sure it’s me that should be looking for the prize money (I’m a sceptic, after all)! You should maybe think of this as what I’d write if I had to referee the $50 million proposal for an MNT development program. I’d recommend rejection, but I’d suggest awarding $2 million to fund these preliminary studies, and ask them to come back in two years to see whether they’ve been able to make any progress in overcoming these objections.

    Phillip, I’m not sure that there is a limit to the number of carbon atoms, but I’d expect there to be constraints on shapes that depart from simple compact clusters.

  4. Richard,

    As a person who thinks that MNT is possible, thanks a lot for this post. This is the type of constructive criticism that supporters of MNT should rejoice in. You have taken the time and effort to understand the Pro-MNT position and have started to come up with research strategies that addresses some of the potentially problematic obstacles that may prevent MNT from being realized (in its current form). I am not sure why the Foresight Institute’s nor CRN’s blogs have not linked to it yet.

    Problem 1, stability of nano clusters and surface reconstruction
    In general I think you are correct, surface reconstruction will eliminate a large number of potentially useful nano structures. On the other hand, surface reconstruction may turn out to be a wonderful tool. Your example of diamond nano-clusters restructuring to have graphite coating could be very useful. The graphite coating will change the optical, electric, and frictional properties of that bit of matter. It will also change its chemical reactivity.

    Researching how use and avoid surface reconstruction should be a very fruitful area of investigation.

    Problem 2 Thermal noise and machine tolerance.
    Once nano engineer comes out I am going to try to design a diamondiod nano-mechanical clock. I will get back to you if I can design one that doesn’t shake apart and keeps a consistent ratio in the movement of the minute hand and hour hand.

    Problem 3 friction and energy dissipation
    A nano-mechanical clock might help shed some light on this problem also.

    Problem 4 design a motor
    I think that this is a composite problem that combines problems 1,2 and 3.
    If a rotary motor turns out to be too difficult one may be able to use an electrostatic actuator that moves a lever between two positions.

    Problem 5 the feed-through problem
    I would like to suggest the the research needed is to design a system of rigid materials that admits say acetylene and rejects oxygen, carbon dioxide and water with a 6 sigma level of success.

    Problem 6 the implementation pathway
    There is some work being done on this issue. There is the Foresight Institute’s Roadmap to productive nano-systems. Chris Phoenix and Tihamer Toth-Fejel are pursing a system that assembles silsesquioxanes (hybrid inorganic-organic cubic monomers) building blocks that looks promising.

  5. hi Richard, Jim

    I think it is good that Richard has put in the effort to think through more of the experiments that he thinks would be useful in validating MNT. I wish you luck in advancing this effort and your soft machines work.

    As noted by Richard, the effort to properly respond and address his points is millions of dollars of effort, which Richard does not have and does not control. I am not saying that this lack of funding or funding control is a Richard just is. I do not have millions of funding dollars to give out either.

    For Jim’s point, “why less notice from pro-MNT people” … it should not then be surprising that more effort and attention is being devoted to convincing people who if convinced would actually provide funding for MNT projects.

    As noted by Jim, Foresight has been funded by over $250,000 to create a roadmap and to have constant engagement on improving and updating it…which addresses point 6. (My guess.. The initial funding was $250K, other companies have signed up, probably funding is north of $500K now). It is also an example that it is more strategically advantageous to try to work with people who are more willing to putting effort towards advancing potential solutions than debating or proving feasiblity.

    There is other work being done to advance MNT. Nanorex simulation and modeling software…other experimental work.

    On Jim’s, what pro-MNT person/group would rejoice over. I will rejoice when billions of dollars are being devoted to making MNT happen instead of the multiple millions now. I will rejoice when many more scientists and engineers and companies are working on fulltime projects to create MNT. I will rejoice at successful MNT computational simulations, MNT experiments, MNT development projects and MNT products. Dialog that leads to those developments are also to be encouraged.

    Merry Christmas and a happy new year.

  6. Well, I wouldn’t want to overstate my influence, but I am flying to DC in February to sit on an NSF funding panel, and I am one of the three scientists on a working party set up by the UK’s funding body EPSRC to make recommendations on how to restructure their nanotechnology programme, which is currently worth maybe $80 million. The main point is that a few million dollars is not a great deal of money in the context of the USAs science budget, or even here in the UK. The reason that this money isn’t being spent on MNT related research isn’t that there’s some political conspiracy against it, it’s that very few scientists have been motivated into writing grant proposals for such work, because, to be frank, very few scientists think that MNT has the remotest chance of working. If pro-MNT people want to change this they need to rejoin the normal scientific process and engage in these scientific arguments. I think that the Foresight roadmap is a step in the right direction (which is, by the way, why I agreed to be a member of its working group), but I do agree with Jim that it is disappointing that CRN and Nanodot didn’t comment on my post.

  7. I don’t think it would do any harm to accentuate how sci-fi MNT is at present. Either money won’t be wasted, or more time is bought to learn how to safely wield such a powerful technology. I only wish you could sit on the panels of other national nanotech funding bodies.

  8. Whether or not MNT turns out ultimately to be feasible, a timeline of 15 years for its development is simply not credible. If people want to continue to make this claim in public, then I think they need to have some convincing answers to these challenges.

  9. People in the US and UK can make almost any claims in public that they want. You can claim that MNT will not work. Other can claim that it will. History can be the judge. As you have clearly indicated anytime you are on a funding committee ..then the pro-MNT groups should wait until after the Feynman Grand prize is won before considering seeking funding from you or even engaging in serious discussion.

    It is useful that you are open about this position. It is also clear why there is no point to debating this issue with you now. After others have helped to fund and perform the work needed to get past the Feynman Grand prize level and your challenges then it seems you may be help to get it the rest of the way.

  10. Brian, it seems to me you have completely missed the point, both of what I’m saying, and of how science works. People can claim what they want, but they have a right to be taken seriously only if they’re prepared to say what the grounds for their views are, and, most importantly, what it would take for them to change their mind.

  11. I’m prepared to discuss with Philip or you Richard or whomever regarding the implications of MNT utilizing electric fields; whether such diamond systems will be scalable. I know this is a little far away from polymer studies, but such systems would need to integrate a wide variety of plastics products in their scale-up… the SPM technique and diamond formation papers I’ve been reading lately are very narrow in their focus. I don’t see this integrated discussion preceding anywhere else in the near future…
    The concept of replicating industrial capital is vital for sustainable human economies (polymer solar cells and possibly CNT hydrogen storage mechanisms). It is necessary to discover just how far away the Von Neumann replicator concept is; if there are any viable near-term chemical/molecular pathways. If the original Drexlerian vision is optimistic because diamond surfaces don’t behave, why don’t we try discussing power hungry STM system architectures? If anyone has the time to set the table for such a long-term discussion, I will gladly show up!!

  12. To challenge number 5: you would just need a way to filter a feed to 100% purity, no? seems to describe one. There also seem to be certain kinds of osmosis where you can get 100% purity (but are often not commercially viable for bulk purification, compared to methods that get 99.999% purity). Not all MNT challenges need to be met with MNT-specific solutions.

    To challenge number 6: I suspect this challenge may need to be solved before much progress can be made on challenges 1-4. It’s one thing to calculate, and argue over whether the calculations include all the pieces. But if you can build an experiment and measure the results, that can greatly reduce the potential for debate (depending on the experiment’s design, and error margins). It may be that most serious scientists don’t see a way they can contribute beyond theoretical arguments – and there’s only limited benefit to be had from theory alone. (Of course, I may be tooting my own horn here – I’m heading up an experiment in applying e-beam lithography to building certain devices of the scale needed to create MNT.)

  13. Phillip, I have been thinking a lot about charge in nanosystems recently, but only in the context of wet systems which is very different. Philip Moriary though has promised me a comment soon…

    Adrian, I think 100% efficient osmotic separation is forbidden by the laws of thermodynamics (when you come to set the free energies equal either side of the membrane you end up with a log(zero) in the calculation) – and to be fair to your link it seems to describe effective but still not perfect separation. But this still leaves aside the practical but important problem of membrane fouling. I absolutely agree with you about the primacy of experiment, and all power to your e-beam lithography work.

  14. By the way – you mentioned a preliminary study of $2 million might be appropriate for tackling some of these challenges, with results needed before, say, a $50 million study would be appropriate. As it happens, my own study (which, granted, mainly tackles only #6, and then in a slightly indirect way) is projected to cost under $1 million – and I’ve no idea where to go for a grant that low, or how to apply. (The experiments thus far have been funded from private sources, essentially on a charity basis.) Might you have any reccomendations?

  15. A $50 million study? That is a sum larger than is annual nanotech spending in many nations. NIAC grants are a good start if you are American. I think $70000 is what their Phase I grants pay.

  16. Some new computational chemistry research which was not made for the purpose of addressing these concerns but which happens to incidentally deal with the surface reconstruction issue.

    Important computational chemistry paper, showing dimer placement reliable at room temperature.

    Zyvex researchers with Robert Freitas and Ralph Merkle have published an important computational chemistry paper, showing dimer placement works reliable at room temperature. (Jing Ping Peng, freitas, merkle, von Ehr, Randall, Skidmore paper on diamond mechnosynthesis) Theoretical analysis of Diamond Mechanosynthesis III : Positional C2 Deposition on Diamond C(110) Surface using Si/Ge/Sn-based dimer placement tools.

    The paper also describes using a first pass of placing every other dimer. Then adding the skipped dimers. This process is a defect-reduced procedure for fully populated dimer rows.

  17. The new paper also discusses tolerances for how precisely things need to be placed at various temperatures with the three different materials. Which I believe starts to address your third point.

  18. Brian, this sort of work is, like the Drexler/Allis work, to be welcomed; it should be combined with a programme of experimental validation to make progress on my challenge 6. Perhaps Philip Moriarty will be able to help, since I know he is still talking to Freitas, and funding may well be available through his “ideas factory” on “Matter compilation via molecular manufacturing”, which has won about $1.7 million UK government funding. Despite addressing the question of positional uncertainty at the tool tip, it doesn’t really address the problem of thermal noise in complex mechanisms which consitutes challenge 2.

  19. Eutatic environments: Until the nanosorters are made…during the transition, bootstrap phase.


    Optical traps

    photoelectrophoretic localization and transport


    Combine the above with MEMS microchannels and reservoirs. Thousands on a chip. Work is being done to extend those up to 250,000+ channels.

    Point 6:
    Freitas going direct to diamond mechanosynthesis.
    Many Millipede-like nanoprobe/nanomanipulator arrays.
    Nuclear technology requires thousands of centrifuges.

    Point 2 and 3
    Design systems that do not generate as much heat and friction. Run that system slower and at cooler temperatures.
    Have designs that are tolerant of more movement. Design end points with more buttressing or tension etc…

    Point 4:
    Until the motor is made. Provide energy to the system with lasers.
    Laser driven molecular action have been demonstrated.

    Make some reduced capability systems that work and are able to make refinements to components. Replace poorer performing components with better components. Bootstrap to better systems.

    Do you still think there are show stoppers to productive nanosystems ? Not necessarily whether a specific rotor design might work but whether a useful set of capabilities seems likely. Where it would make sense to spend money, time and resources to validate and explore exactly how far we can take it ? ie. pay for the more experimental and theoretical work.

    The domination of theoretical work has been because it has been cheaper and those who could fund the experimental work have held back. I expect Zyvex and some of those wealthy from the will provide funding. Others may follow.

  20. btw re fouled membranes: with the many channel redundancy one could circumvent a channel with a fouled membrane. Then swap it out.

  21. I am kind of unusual as an observer of the nanotech scene, in that I am neither convinced that the Drexlerian program will work, nor convinced that it won’t! Hard to believe, but almost no one falls into this category, although it is IMO the only reasonable position.

    One big problem I have arguing with pro-Drexlerites is the issue of “burden of proof”. They often argue, as Brian Wang does two posts above, that there are a lot of ideas that might work, and it is up to opponents to come up with exhaustive proofs that the technology will fail. I have tried to point out that given the radical and extraordinary claims for this technology (human immortality, and machines that build anything instantly that you wish for, among others), the burden of proof needs to be on the proponents of the technology to show that it will actually work. Until that is done the appropriate response is, we’ll see.

    I applaud Richard for coming up with his list of challenges for the Drexler vision, which has been rather spectacularly ignored by the molecular manufacturing community in the months since he posted it. On the other hand I don’t think you can conclude from these objections, “therefore, it probably won’t work,” as Richard sometimes seems to. We simply don’t know, and it is too early to say, whether these and other problems can be overcome.

  22. What I am saying is that progress continues to be made and a significant proof of a key aspect was done. How much of challenge number 1 is left ? More computational chemistry work will still be done but does it look like that it will be a showstopper anymore ?

    I am curious as to how much progress happens before various skeptics start to modify their opinion and when some significant research money will flow to this area.
    In my opinion it is becoming clearer and clearer that a lot can be done.
    If necessary and one was not more clever then you could get around potential complications using bulk scaling.

    The surface reconstruction and stability stuff … if it was a problem might prevent even a few mechanosynthesis steps. So the new work is making it pretty tough to claim it can’t be done at all.

    I am not saying that workarounds might get us to immortality or build anything instantly. (the actual claims are repair cellular level damage which should greatly extend life span and build a lot more things a lot faster). I am saying it should be clearing the first hurdle that a lot more money should be spent on something that is very promising versus other tech spending possibilities. Even if one thought 60 years ago that one could make a handheld petaflop supercomputer, do the proponents of an Eniac project have to first prove that they have an implementation path to that machine ? I am saying that we are likely to be able to make an nanotech Eniac and get on a cycle of progress for products that are better and useful. We should research making the MNT equivalent of vacuum tubes, transistors and basic computer architectures. Maybe divert some money from researching the mating rituals of spider monkeys or buying that 12th aircraft carrier group.

    Some money has to be spent and some precursor stuff has to be made first. The burden of proof being on the propenents is fine. But it is not reasonable to say prove it with volunteers and your spare time. The proof may still come but it will take a lot longer in bootstrap mode. Fusion energy research can be more criticized because they have had 40+ years
    of funding at billions of dollars per year. Molecular nanotech has had almost no public funding. The NNI billions are almost all going to nanoparticles and nanomaterials.

    Claims get made all the time. Money, resources and time need to be spent to explore how well things really work.

    The argument seems to be that the claims are too promising so we do not want to fund it yet.

    I am saying. Enough has been done to show something worthwhile seems likely. It is potentially very promising. We should spend the research money and effort to find out how much we can do and try to get more of the first steps done.

  23. Hi Hal, Wang

    Will some of the ideas behind Molecular Manufactoring work. Bien Sûr!
    The real problem are about cost effectiveness! All of the examples that Wang put forward are for geeks exciting but not Drexlerian exciting!

    I mean, what entrepreneur is going to fund an molecular factory if that factory will be copied and distributed for nothing?

    Now onto physical show stoppers. Basically, due to thermodynamics, atomic precision is an oxymoron. Large assemblies of atoms will spontaneously rearrange themselves to the LOWEST ENERGY POSITIONS. Sure molecules of say 5000 atoms can be precisely placed, but even large molecules of say 1000,000 atoms have many different arrangements! Even Diamond is not bonded to atomic precision!

    Now, for a LIMITED number of materials, you might get APPROXIMATE atomic precision like Carbon Nanotubes. But even here it is defects per billion! Most people hope to improve this to parts per trillion and onto Space Elevators, but atomic precision RIEN.

    Finally, if you COMPROMISE on atomic precision, then why bother with Molecular Factories?

    An amateur mathematician

  24. If molecular manufacturing was just what Zelah indicated. A way to better and new materials… making a wider range of things similar to carbon nanotubes in terms of new stable arrangements of lowest energy position structures.

    Those are still many billion dollar industries

    Might be worth investing a few hundred million in research to check that out.

    Music CDs and movie DVDs get copied and in spite of all the whining by those industries about $6 billion lost to piracy those entertainment industries still manage to make about $30 billion in the USA and $100+ billion worldwide. Are the carbon nanotube factories becoming uneconomic due to piracy ? They are just tubes of carbon. When are you planning to copy those? Others are making millions supplying them. Yes, why bother making billions when maybe in a couple of decades you could have a bad piracy problem. That is a puzzler.

    Is the debate between whether there are multi-billion and maybe trillion dollar industries or whether there are society changing cell repair and manufacturing ? It seems even the worst case is worth researching.

  25. Hi Mr Wang,

    You are not answering my points in the spirit they were set!

    If the economics of Nanofactories are to be the say as say Music CD’s, then SEVERE restrictions would be in place for users of these products by LAW.

    This is not the fairyland of Drexlerian one size fits all Nanofactories! If there are even MILD restrictions on their use, you can bet that ‘The Singularity’ will be more like a WIMPER!

    My next point which is that Large molecules are not RIGID seems to have passed you by! Even Diamond / CARBON NANOTUBES may not be RIGID enough!

    The point is that maybe only 2 to 3 compounds are RIGID enough to be molecular assembled in the Drexlerian way!

    Yet again I ask, if errors are to tolerated, what is the point?

    An amateur mathematician.

  26. Hi Zelah

    1. I do not agree with your opinion that there are only 2 or 3 compounds rigid enough to be molecularly assembled in the Drexlerian way. In this venue, the background has been the 6 challenges to molecular manufacturing proposals. I have not heard a clear indication that the lets not do it because it is scientifically impossible is off the table. You appeared to have moved it off for yourself

    2. The USA and other countries are willing to spend billions on basic science, where we do not have any idea of possible return or application. Here we have something which is clearly interesting and could have a lot of return. Where significant work has been done to lay theoretical and experimental proofs of likely viability for further investigation.

    3. I think Nanofactories could work, but in this thread I was talking about a massive infrastructure during the transitionary phase. So it was not a “one size fits all Nanofactory”. I submit the fairyland is your misunderstanding of some proposals. If 1890 someone draws up some proofs that heavier than air machines should be feasible and should be funded, then you would say hey we should not try to build those because although it will probably work but I don’t think everyone will have flying cars. The heavier than air flying world will be no big deal.

    4. You are saying large molecules are not rigid enough. I know that you are arguing against the larger vision and projections. I said in point 1, not relavant to immediate exploratory funding.

    Plus combination molecular mechanical action is already possible
    So if you can scale that up with mechanosynthesis then you are saying this is still not interesting and useful ? You are saying that even if we use diamond which is firmer than these molecules that it would not be useful and that we could only make 2 or 3 compounds. Which 2 or 3 compounds ?

    DNA nanotechnology uses even floppier DNA.
    DNA tweezers, DNA walkers
    They are braiding the DNA to make them firmer.

    5. What errors to be tolerated are you referring to ?

    6. What is the point?

    Precise filtering is a multi-billion dollar market.
    Floppy carbon nanotubes are multi-billion dollar markets.
    Diamond synthesis is multi-billion dollar market
    Better molecular sensors are multi-billion dollar markets.

    nanofactory economics
    Here is a deeper analysis of what the economics might be with nanofactories

    Instead of debating the hypothetical, the next stages of theoretical and experimental research should be performed to try to answer all of the detailed issues.

  27. Hal, you are of course quite right. There is no proof that the Drexlerian program won’t work (in principle, at some level, in some conditions…), and this is the position I’ve stated many times. And yet, the longer time goes on, not just without significant progress from the MNT camp, but without evidence that they even understand the scale of the challenges or the preliminary work that needs to be done, the less likelihood there is of this stuff coming to pass. I’m reminded of a comment made in the Nottingham nanotechnology debate by Laurence Eaves, a nanoscientist of considerably more experience and distinction than me, in response to the MNT proponents. “You keep saying, this or that won’t be a showstopper. But I don’t see any show-starters.”

    In specific response to Brian, the point in challenge 1 is much more general than whether this or that mechanosynthesis step will work. It is that, currently, we do not know whether the structures being drawn as targets for the mechanosynthesis – the rotors and cogs and gears – are chemically stable under any given set of conditions, let alone whether the necessary intermediates are. Chemical stability is about much more than just satisfying the valency, and none of us are able to do density functional theory in our heads.

    As to the issue about research funding, I don’t think that’s the problem. There’s loads of research money going into basic nanoscience (i.e., stuff that goes beyond nanomaterials and nanoparticles) around the world; the problem is not that the money isn’t available, it’s that very few scientists have chosen to work on MNT. Of course there are political considerations on the way research spending is allocated, but ultimately it’s the worldwide scientific community itself that has the biggest influence on deciding whether some area is pursued or not.

    To give an example, I’ve spent the morning working on a lecture about DNA nanotechnology. This is a fascinating area in academic nanoscience, quite close to the original vision of Drexler in terms of making devices and machines at the nanoscale, but utterly different in its design philosophy to the Nanosystems mechanical engineering paradigm. It’s still very much a niche activity; there’s no prospect of any early economic return on the work, yet the level of activity is orders of magnitude than we see in MNT. This morning I’ve sifted through more than 500 papers in the area (running through all of those that cite an important paper from 1998), across the world there are probably several hundred people working on related problems, trying out different experimental approaches, doing relevant theory, with important contributions from the USA, the UK, Germany, Ireland, Israel, China and others. Why has this happened? There’s been no international summit, no announcement of a Manhatten project, no top-down direction of research funds. On the contrary, I’ve heard complaints from leading activists in the area in both the USA and the UK that they find funding pretty hard to come by. What’s happened is that a lot of scientists have looked at the efforts of the pioneers, they’ve assessed what’s possible, they’ve made a judgement about the future promise of the field, and they’ve piled in, raising money from wherever they can. Contrast this with the MNT program, with its handful of papers and tiny core of activists. The failure here is not that MNT supporters have not been able to persuade governments to fund the area, its that they have not been able to persuade scientists that the idea is worth pursuing. And you only have to look at the recent discussion on CRN’s website, where Chris Phoenix arrogantly dismisses critiques of his ideas with phrases like “Unfortunately, after a number of exchanges [with Jones], I found it unproductive to continue talking with him”, yet continues to make claims that 3 seconds thought and a few back of the envelope calculations reveal are completely absurd, to see why scientists might conclude that MNT proponents are just not serious.

    My apologies for sounding slightly tetchy, and my thanks to Brian, Hal, Zelah, Phillip and others for being at least willing to discuss things, even if we don’t agree about everything.

  28. What I find disingenuous Richard is that a paper gets published which is based on 10,000+ hours of computational chemistry using the density function that you were asking for in point 1. They were not just checking the valency. So are you moving the goal posts ? Are you at least going to admit that they did validate using the density function that you have claimed is necessary?

    So you are saying that until some multi-thousand atom simulations are done on some targets then you will say what ? What about all of the intermediate steps. Interesting. So what are the largest computational chemistry simulations that have been done ? How much computing power is needed ? And that costs how much and has been possible for how long ?

    I think the “why has that not already been done” statement is that without big prior funding it has taken time for certain things to become more affordable to do.

    I do not think there have been a lot of claims that this would be easy. It does require funding and a lot of work. The claims have mainly been…seems to be not physically impossible and worth trying.

    DNA is easier to work with. Billions were already spent on the human genome project to sequence DNA. There is a lot of spin off tools from that and a lot of researchers got experience from it. There is a shift and learning curve that would be required to work on Mechanosynthesis. Plus a lot of work follows funding. Fields of tech have been boosted from the funding side before.

  29. Another reason why there are fewer MNT researchers and fewer declared MNT supporting scientists. It is currently not that safe a career choice. There are those who make it not a choice of OK that is an equally legitimate area of research.

    If I am making a career choice in business then I also look at how tough the career path is.

    So we get a research environment where most researchers are scared to do the really risky things.

    It is similar to the difference in the dynamic for entrepreneurial businesses. In places, like Silicon Valley where there is less stigma to trying to start a business and not succeeding there are more entrepreneurial attempts and more successes. Most other places have more stigma on fail attempts and less support for those attempting. Thus the first big successes in new areas often come from Silicon Valley. Follow on competitors come from other places after the idea has been proved to be safe.
    eg. Back in 1997, Oh you want to try to make another Yahoo or Netscape. Now that they have IPO’d that makes sense. But before in 1993 or earlier. Oh you want to try to make Mosaic into a business or try to research making something like this thing you call a browser. That will never work. We have been using the internet for the last 20 years for email and scientific file sharing. There is no money in that. Look other people are researching how to make a better spreadsheets. Now that makes sense. If you try to make anything commercial on the internet (1993-1995) and fail we will laugh plus you will have to do it on your own dime. But hey we will give you $1 million to try and make a better spreadsheet and if you fail…hey no biggie…Microsoft and Lotus are tough. Or how about some military cruise missile control software. The government spent X billions of dollars on that.

  30. the no progress charge up to this point carries little weight. Why ?
    The tools are only now becoming good enough for some progress.
    The early 1980’s book was based on the projection that if tools, computers etc… kept getting better then we could start doing this.

    It is like saying hey where is that result that you said would take a petaflop computer 6-15 years to calculate ? Your lack of progress from when you said it would happen clearly shows that this is not worthwhile. You clearly do not know how tough a problem this is and your lack of progress shows that it will never work. Hello. The first petaflop computer is being built this year for $100 million + and we will not get to use it.

    What is the significant progress that could have happened that has not ?

    ie with 1990’s equipement costing less than $100,000 at the time what could have been done.

    Molecular electronics is a sub-section of the problem for molecular manufacturing. Quite a bit of money and people have been trying to crack that problem. They have not replaced the semiconductor industry and have not gotten a commercial device out yet. Is that never going to work? Why have not the majority of Intels research dollars gone to molecular electronics.

    The IBM millipede project has not commercialed STM arrays for commercial hard drives. That is also an easier problem than MNT.

    Therefore, the they do not know how tough the problems are charge is also wrong.

    the charge of lack of showstarters. If you spend your time looking for reasons not to do something then you will always find them.

    I find it especially curious the why have not more researchers gotten into this area. When you and the Laurence Eaves of the world are taunting everyone who does get into it and actively trying to cut off funding.

    eg. Hey have you 5 guys built that 500 story building ? Still only part of a foundation, that’s lame. You had to write the new computer aided design software and start working on new tools to help in the building process. No one has built over 200 stories. Why aren’t other guys coming to help you? You did not know how tough a problem it was. I am going to stop the city and federal government from trying to give you money. Even if you can do it, no one needs a 500 story building and it will lose money. Me and my buddy Laurence and our friends will just picket you every day until you give up. But remember I am fair and balanced.

  31. btw: the first 1981 paper by Drexler discusses protein engineering and using DNA and RNA as a path to nanotechnology.

    Although the diamond mechanosynthesis work has been a lightning rod for controversy. I do not see how anyone could claim that Drexler supporters have not wanted progress for the protein engineering and DNA nanotech side of things, just because of statements is that diamondoid mechanosynthesis could be theoretically more powerful.

    It is weird that since the very beginning protein engineering and DNA nanotech has been discussed as a way to do things.

    ie. Hey you talked about several things back in the 80’s and 90’s, I want to champion this part and pretend that you are against it and that you only promoting some long term goals. that way you will look less credible and my 2004 book will be the first time someone talked about soft machines.

    The DNA nanotech guys were at the conferences that your group organized from the late ’90s through last year, Ned Seeman is on various committees related to Foresight but DNA nanotech is credible and not related to what you crazies are doing.

    So any part that starts working lets drive an imaginary split into it. And say OK that is credible and successful but your ideas are still not working.

  32. The latest Freitas et al. simulation demonstrates the theoretical viability of mechanosynthesis at 300K of flat and slightly convex/concave surfaces. It also provides a chart for future reference that illustrates tool tip positional uncertainties under 4 temperature regimes. I expect future simulation to broaden the space of simulated geometries and I expect someone to eventually attempt the simplest dimer mechanosynthetic step.

    Part of the frustration felt by MNT enthusiasts is that an exponential manufacturing system capable of dropping the raw materials price of diamond down to the price of methane, and maybe drop the price of sp2 carbon allotropes too; such a manufacturing technology would be worth many orders of magnitude more than would be any DNA pharmaceutical or biotech, technology.
    MNT proponents are relatively stupid in comparison to the opposition. Right off the bat you have a Nobel prize winner like Smalley who had many CNT insights and many visionary ideas how CNTs could transform the world’s energy infrastructures, attack Drexler’s MNT position. Regardless of whether the criticism was valid or not, it isn’t a friendly portend for the introduction of the MNT concept to the scientific mainstream. Drexler, Freitas, and Phoenix are all approaching MNT through the eyes of theoretical physicists. And they may get steamrolled in debates by SPM practitioners on points that would be elementary had MNT proponents endeavoured an SPM diamond surface chemistry education. But then they probably wouldn’t have become aware of the MNT concept in the first place. It is a catch-22: being asked to develop theory and then defend it on an SPM battleground. It is like telling Einstein to become an astronomer to test his new theories.

    Zelah, if there are error structures of a few parts per billion, the error structures can just be junked. Just need to keep assembly modular and incorporate error-inspection along the way. I don’t think it is useful to view surface reconstruction in term of 5000 atoms vs. 1 000 000 atoms. Surfaces of any size can reconstruct. Maybe more useful would be to assess a surface area/volume ratio for any diamond structure to be dimer-modified.

  33. Brian, to be brief: Density functional theory was invented in its current form in the late 60s, and it’s now a completely routine technique in computational chemistry. As I made clear in my original post and in my answer to your query, the fact that it is being used in calculations by the MNT community is to be welcomed, but one swallow doesn’t make a summer. It’s good to check out whether some particular mechanosynthesis step is possible, but this doesn’t yet address those serious and central issues in challenge 1. As to other tools, the key one is clearly scanning probe microscopy, invented 1981, fairly widely spread in the form of home built instruments by the late 80’s, and available in the form of easy to use commercial instruments by the mid-90s. I’d guess that there are now thousands of these instruments around the world, with most serious research universities having at least half a dozen of them.

    As to me and Eaves actively trying to cut off funding, you’ve got the wrong targets. It’s Eaves’s younger colleague at Nottingham, Philip Moriarty, (perhaps not coincidentally, also on CRNs hate list) who has extracted what is perhaps the largest sum of any government’s money to pursue a program explicitly mentioning molecular manufacturing (its title is “Matter compilation via molecular manufacturing”, and, for what it’s worth, I supported this proposal). And I’ve ensured that “Extreme nanotechnology and molecular manufacturing” appears as a sub-heading in the classification that our national nanotechnology program uses. What you don’t seem to understand is that Moriarty and I are pretty much the most pro-Drexler mainstream scientists currently around at the moment, simply because we take the ideas seriously enough to give them a real critique. I have extensively given Drexler credit for appreciating the power of biological and soft approaches to nanotechnology. But I think (and I don’t just assert this, I support it with extensive and detailed arguments) that the arguments that are made to suggest that the diamondoid route will be dramatically better are, at best, unproven. If the MNT community disagree with me, then they should make some technical arguments in rebuttal, not flounce off saying that the discussion is “unproductive”.

  34. Richard

    Your charge that “Chris Phoenix arrogantly dismisses critiques of his ideas with phrases like “Unfortunately, after a number of exchanges [with Jones], I found it unproductive to continue talking with him”

    You were harping on point 1. That the surface reconstruction problem would be a showstopper and that even a few placements would reconstruct. So in the meantime, 6 other researchers perform 10,000 hours of density function computational chemistry and some months of work on that point and show that a bunch of placements can happen without reconstruction. Your response is still not enough. More simulations of not just 200 atoms but thousands or millions of atoms.

    So what would the point have been of continued conversation ? The simulations would still not get run in between emails or postings.

    You would still say, hey I don’t like Chris Phoenix projecting past what can be proved in a computationally correct simulation backed up by experiments.
    Those guys in 1980 claiming that scramjets could work. Should have kept their mouths shut until 2005 when the first prototypes got working.
    The fusion energy guys need to shutup.
    The climate change guys should shut up too, clearly that is still controversial and unproven.

    Chris Phoenix arrogantly dismisses critiques and Richard Jones arrogantly dismisses the computational evidence that is part of what he himself called for a few months earlier.
    It remains a mystery why the two cannot have a productive conversation.

  35. Brian, you were not party to my exchanges with Phoenix, many of which were not public, so you’re not in a position to judge why the conversation was not “productive”.

  36. Well we can talk about this in detail and all the other things that I said that you are wrong about. Or is it that you are OK lobbing criticisms but cannot take being criticized ? In the meantime, I will take your silence on the above criticisms to be acceptance and avoidance on your side that you are wrong. Point by point rebuttal with evidence will be fine.

  37. There was an update delay in the site and I did not see your lengthier two paragraphs. I will accept that you believe that you are trying to be helpful.

    My belief is that more of a technical response will come in the new book
    That Freitas and Merkle are working upon.

    Diamond Surfaces and Diamond Mechanosynthesis (2006-7, in preparation). A full analysis of how to use programmable positional assembly to synthesize most arrangements of atoms permitted by physical law would be, at present, prohibitively complex. A more manageable project is to analyze a significant class of stiff hydrocarbons – in particular, diamond – that could potentially be synthesized by the use of a small set of positionally controlled mechanosynthetic tool tips. There is already widespread interest in the exceptional properties of diamond such as extreme hardness, high strength and stiffness, high thermal conductivity, low frictional coefficient, chemical inertness, and a wide bandgap. The molecular surface characteristics of diamond were extensively investigated both theoretically and experimentally in the 1990s, and many practical questions about the molecular structure of diamond surfaces have now been resolved. The fields of diamond CVD and adamantane chemistry provide additional understanding, both experimental and theoretical, of the myriad reaction mechanisms which can contribute to the growth of diamond.

    A technical bibliography for research on positional mechanosynthesis is available here. The first patent ever filed on positional diamond mechanosynthesis is available here.

    Plus further papers and work from Freitas, Merkle and Zyvex and others.

  38. Hi Philip,

    Thanks for your answer.

    “Zelah, if there are error structures of a few parts per billion, the error structures can just be junked.”

    Gets to the heart of the problem.

    I know that you might think that this is silly, but believe me it aint! How exactly are one to junk incorrect structures? For me, I have never had a problem in manipulating MOLECULES around the place. It has always been when one aggregates these molecules into larger macromolecules.

    Now Philip, and correct me if I am wrong, I believe that your position is that first work with Diamond production via molecular manufacturing, and worry about other types of molecular manufacturing later. Now in THIS PARTICULAR CASE, ditching parts which are not positioned correctly is conceptually easy. When one is moving hundreds of different molecules at the same time, it gets an whole lot harder!

    My belief is that Molecular Manufactoring will work only for say Diamond / Carbon Nanotube with errors per trillion per say. In other words, when simulations of millions and billions and trillions of atoms are done, STRUCTURAL reconstruction will prove to be the norm!

    The good news is that Carbon nanotube production with errors per trillion is one of the holy grails of Carbon nanotech.

    But building say comsumer products in the home? Almost certainly uneconomic and frankly will seem just like the SF predictions of everyone going to work in the personal aircraft!

    An amateur mathematician.

  39. Zelah

    Richard has already announced that we cannot perform functional density simulations in our heads. So if he gets annoyed by people saying that something might work without the computer simulation to back it up then one should also not claim that it won’t work.

    Just out of curiousity though, why do you think that if 200 atoms work without reconstruction as shown in the last paper that at a million atoms reconstruction will reassert itself as dominant ? Just a hunch or have you had experience watching the diamond on a diamond ring start to reconstruct ?

    Also, it seems that people who criticize molecular nanotech like to extrapolate out to absurd levels without any modification. Similar to statements like if humans kept breeding at the rate of the 1950’s then by the year 4000 the mass of humanity would be more than the planet. Or a person could not drive from New york to London because they would drown in the Atlantic. The planet can only support 3 billion people who consume like americans in 2006, we have to kill 3.5 billion people.
    The rate of breeding changing somewhere between 7 billion and 100 billion? Designing the equivalent of a nanotech boat, submarine or airplane is too clever to get from NY to London. Not only that it would be uneconomic and not worth it. Making devices and systems and city planning more efficient so that people could comfortably live on 10% of the consumption or getting more resources from other places is not the better choice ?

  40. Maybe I am falling into that technique of pro-MNT people. Boats, submarines and airplanes are list of proposals that might work to get someone from New york to London. I better go run some computer simulations and experiments to prove it before I make that claim.

  41. You can drive over the pack ice in winter. If you bring enough supplies you can make it to a road in Russia and take the chunnel from mainland Europe to London. There is no need for nanotechnology to achieve this particular feat.

  42. Michael Vassar had the following to say:

    “Empirically validated engineering techniques don’t fail when applied in new domains 1/6th, 1/10th, or 1/20th of the time. Conjunction fallacies are probably operative if a person sees MNT as a nearly sure thing, but basically I don’t think that MNT looks harder than some other (mostly military) technologies that are seen as a matter of “when”, not “if” by all involved. If it wasn’t for the magnitude of the consequences no-one would think it was impossible or permanently impractical.

    I think Robert Frietas has gone a long way towards answering question 1, though more work is needed.

    The main real problem here that I’m uncertain about has to do with getting rid of the phonons that result from bond formation when molecules are added to an assembly. My one possibly significant MNT construction insight has been a proposed way of dealing with these phonons, but I don’t know if my proposal will work and consensus is that it isn’t necessary.

    Thermal energy can always be reduced with low temperatures, and if diamond doesn’t work at higher temperatures other more stable rigid molecules can probably be used for higher temperature applications, but we know that molecular latices of dozens or hundreds of carbon atoms in diamond form are stable at room temperature and far above empirically. As a result, I’d be very very surprised if problems 2 or 3 are show stoppers, though much less surprised to learn that some of the exact designs in Nanosystems don’t work. A factor of 2 or 3 slow-down, a small reduction in some forces that can be applied, or the need for slight redesign may effect take-off speed, spreading the first year of radical transformation over two years, for instance.

    Problem 4 is that a particular component might not be workable, but there are probably other ways of designing motors, only one guy was needed to find this one very early in the field’s history. In any event, motors aren’t essential to MNT. Diamond or nanotube pistons can transfer forces from the macroscale to the nanoscale and transmit them through the body of a block of machinery.

    Problem 5 is basically just saying “I think that all of the input-output channels used by bio have no non-solution equivalents” even though conceptually there is no reason to expect this. It would work, if anything, much better as an argument against biology. In general it’s very easy to see how interfaces could work.

    Problem 6 is basically equivalent to saying “it hasn’t been done so it probably can’t be done”.

    Problems 5 and 6 basically constitute strong evidence against Jones’ neutrality, but parties can be non-neutral and still informative.

    You can cross-post this to “Soft Machines” if you wish.”

  43. “Problems 5 and 6 basically constitute strong evidence against Jones’ neutrality, but parties can be non-neutral and still informative.”

    I must have missed the clause that said bloggers (or indeed scientists) have to be neutral! Of course I’m not neutral; I have plenty of opinions, as well as more than a few cultural biases, some unexamined preconceptions and even the odd emotional reaction. I aspire to be fair, to be reflective, to be open to new perspectives, and to argue my positions in a way that reflects the better traditions of the science I’ve been trained in, but I don’t see why I should aspire to be neutral.

  44. ICE pistons are driven by gasoline explosions. What is the the modus operandi for diamond pistons? Photons? If so, how to make the laser light source scaleable? Not necessarily a show-stopper, but we are far from Nanosystems turf (electrostatic motor of still unforwarded design) here, I assume.

  45. Richard,

    Can you name some people in the anti-camp that don’t take Drexler’s ideas seriously, aside from that one guy you cite frequently? I just want to get an idea for who they are. Right now I am much more familiar with the pro-MNT side.

  46. People who are on record criticising Drexler’s ideas include, of course, the late Richard Smalley, George Whitesides, Stan Williams, Don Eigler, Heinrich Rohrer and James Tour, to name those for whom I can immediately identify a written source.

    One also needs to be precise about what one means by Drexler’s ideas. Some people (and I think I fall into this category) can find positive things to say about Drexler’s role in formulating a vision of molecular size machines, yet disagree about the route proposed in Nanosystems to achieve such machines. For example, in the monograph by Balzani, Credi and Venturi, Molecular Devices and Machines (which is a very detailed account of the supramolecular chemistry route to molecular machines pioneered by Fraser Stoddart, and is therefore very much not focused on more mundane nanomaterials work), they say: “The fascinating, but somewhat abstract ideas of Drexler about the construction, futuristic use, and frightening potential of nanomachines have been sceptically and ironically commented upon by a large part of the scientific community…. It should be recognised, however, that Drexler’s visionary ideas have at least had the merit of drawing the attention of people to science and influencing many scientists to direct their research projects towards the fascinating world of nanotechnology.”

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