Drexler and the nanosubmarines

I wrote below about Drexler’s unhappiness that I had illustrated my article in Physics World with a particularly
silly image of a nanosubmarine. He wrote that could not be held responsible for the “ridiculous artists concepts” that have become associated with his work, and thus my criticism of the nanosubmarine illustration wasn’t a fair criticism of MNT. I’m quite sure that if Drexler had been directly involved in the production of images like these, then they would be much more physically plausible. But I wonder if the supporters of Drexler have been as quick to seek correction when these images are used in connection with articles that are positive about MNT? The particular image I chose is very widely circulated, as it appears on the Microsoft Encarta online encyclopedia with the caption “Nanobot computers of the future” . Many readers – particularly high school students – will regard this source as authoritative, and it is perhaps a pity that this image remains unchallenged there.

The neutral onlooker might also find it puzzling that exactly the same image appears on the website of the Foresight Institute, of which Drexler is Founder and Chairman Emeritus. Of course, Drexler can’t be held responsible for everything on this large website, particularly given that he has no executive role. But the casual browser must surely be forgiven for thinking that images on the Foresight website carried some kind of endorsement from the Foresight Institute, and thus by extension from its Board chairman.

But the issue of the use of imaginative images is far from black and white. I gave a talk at a conference in May in which I made similar criticisms of this kind of image, and I was surprised to be taken to task about it by a prominent member of the UK nanobusiness community. His argument was that I should consider the image as a metaphor, and if the public found it easier to understand the image of a nanobot vacuum cleaner sucking up cholesterol deposits than a more realistic picture of, say, an anti-cholesterol drug wrapped up in an advanced nanoscale drug-delivery device like a liposome, then the imaginative image served a valuable purpose. Perhaps I’m too literal minded to buy this argument. The message must surely be that visual metaphors are very powerful, but if not used carefully they can rebound in unexpected and unwelcome ways.

Making me a better human

An interesting article on the Better Humans website, Unraveling the Big Debate over Small Machines, quotes me, and adds that my position on nanotechnology isn’t very different to Drexler’s. This is at first sight rather puzzling since my recent article in Physics World, The Future of Nanotechnology, and indeed my book Soft Machines, have been read by many people, including Drexler himself, as attacks on the Drexlerian position. Indeed, I would say myself that my views are actually pretty similar to those of MNT arch-sceptic George Whitesides, though I possibly express them a bit more politely, and with a little less self-confidence.

But on reflection, I find this rather a welcome perception. Perhaps it does mean that a space is growing on both sides of the debate for some rather more nuanced positions than we’ve seen in the past. The Better Humans article gives a lot of attention to the Drexler-Smalley debate. It seems to me that we need to move on from this. MNT sceptics need to recognise that Smalley did not deliver the knock-out punch that they were hoping for. This was brought home to me in Santa Barbara this week in a conversation with an old friend who teaches a sophomore class in nanotechnology at the University of Pennsylvania. She’d set her class the task of studying the debate and deciding which side they thought had prevailed; an overwhelming majority favoured Drexler. So a reasonable sample of educated and intelligent young people was not convinced by Smalley. On the other hand, I think that MNT devotees are wrong to think that this means there are now no rational grounds for scepticism about MNT. While the possibility of some kind of radical nanotechnology is proved by the existence of biological nanomachines, the question of what the best approach to making synthetic nanomachines is is by no means decided. My book Soft Machines argues that MNT has many more disadvantages and potential difficulties than some of its supporters admit, and it will be interesting to see whether its arguments prove more convincing than Smalley’s.

Drexler responds

This morning brought a somewhat tetchy email from K. Eric Drexler, not entirely happy about my article in Physics World, The future of nanotechnology. There were three main complaints:

1. That he, Drexler, could not be held responsible for the “ridiculous artist’s concepts” that have become associated with his work. Thus my criticism of the nanosubmarine illustration isn’t a fair criticism of MNT. Actually, I have some sympathy with his predicament on this, in that I’m sure that the elementary errors that show up in the particularly silly image I chose wouldn’t be there if Drexler had had anything to do with it. Nonetheless, my criticism of these images does make one important point very clear – you shouldn’t expect macroscopic engineering design concepts to apply to directly to the nanoworld. Is this a fair criticism of MNT? I think it is – to quote from the preface of Nanosystems; “Molecular manufacturing applies the principles of mechanical engineering to chemistry”.

2. Next he argues that my statement that “Strong surface forces may make the moving parts of a NEMS device stick together and seize up” reflects a lack of study of the appropriate section of Nanosystems, chapter 10, which argues that very low friction is to be expected between atomically smooth diamond surfaces. It’s worth noting first of all that this statement in my article isn’t actually directed at MNT at all, but at top-down NEMS. Nonetheless, I do believe that the discussion in Nanosystems does substantially underestimate the problems of friction and dissipation at the nanoscale. This is a rather technical discussion, which I will enlarge on at a later time.

3. Finally, he objects that I have not proved my central contention, that biology is highly optimised for the nanoscale, pointing out that biology hasn’t been able to explore the space of non-aqueous molecular machine systems. This gets to the heart of the argument of Soft Machines. A crucial, though obvious, point, is that it only makes sense to talk about optimisation in the context of a particular environment, and what is optimised for ambient operation at 300 K in the presence of water is not the same as what is optimised for ultra-high vacuum at a temperature of 3 K. I wouldn’t exclude the possibility that MNT would work at 3 K in UHV, but I think that what works in ambient conditions is much more interesting, if only because medicine is likely to be such an important application of nanotechnology.