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« Biplanes & Nanofactories | Main | Research Directions »

May 09, 2005

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Brett Bellmore

Doesn't seem to have been changed all that much since the conference last October, when they took a collection to update it to reflect current concepts. I wonder how that's going?

jim moore

Here is a link to version 0.95
http://www.foresight.org/nanofactory/nanofactory.mov

Again it is a big file.

Favorite change - seeing benzene being rejected by sorting rotors.

Thing I would most like to change - I would have liked to see the parts made by molecular mills being assembled into ~ 200 nm functional blocks and those blocks then being assembled into a macro scale product.


Next step? An online multi-person nano-factory design simulator. Rather than spending your time on massively-multiplayer online role-playing games the truly geeky could spend their time filling in all of the additional designs needed for a nano-factory. Remember the devil is in the details and their are many many details that have not been worked through yet. ( Can your section of the nano-factory withstand the thermal vibrations at 200K ?, 300K?, 400K? What happens when your section is hit by comic radiation? Is your section working at a complementary frequency with the other sections it is connected to? etc. etc.)

jim moore

"What happens when your section is hit by comic radiation? "

My designs will laugh at comic radiation, (take that Lenny Bruce)

Cosmic radiation is a different matter entirely.

{UGGG!! I hate when my brain sees what it wants to see rather than what I actually wrote.}

oker

Seems that the new idea of molecular manufacturing systems has gotten around the 'inefficiency' of having a single complex lots of billions of atoms all in the right place assemblers to place single atoms for a macroscopic object with all their atoms in the right place to make atomically precise macroscopic objects.

But wait! What if these new macroscopic mnt's go off on a self-replication spree? Ooch! I guess at least you could see them!

And what about placing that single atom in a billion atom molecule in the right place out in the environment when you really need it?

And what about this transhumanist downloading into a single mind so that nobody has an ich to be single greedy little bastards? Maybe that gray goo idea wasn't such a bad idea! After all, wouldn't that 'decode' humanity and stick them all in one basket?!

Hal

I made some comments at http://lists.extropy.org/pipermail/extropy-chat/2004-October/010311.html on the earlier version of the movie. The points about the low level molecular assembly phase still apply. We see sticky fingers problems here, with no explanation of why the C2 is held so firmly during the initial hydrogen abstraction yet released so easily during final deposition. Note that recent simulations of C2 deposition showed a tendency to stick to the tool and not to the work piece, and those didn't even have to worry about holding it tightly during an abstraction.

And we also don't see how the other various tools are recharged. We see a tool pulling off a hydrogen, but we don't see how that tool drops the hydrogen to be ready for the next cycle. (And if another tool pulls it off of that one, then how does the new tool get recharged? Don't we have an infinite regression here?)

We also see potential "fat fingers" problems for the reaction where three tool tips have to come together in a precise geometric arrangement. Merkle's hydrocarbon metabolism paper, which seems to have influenced some of the concepts here, had some reactions where four tooltips were involved, making the problem worse.

Basically, without more details about the chemical reactions involved, this first part of the movie is worthless in terms of establishing the credibility of the concept. For all we know, every step shown could be physically impossible. This movie should only be an adjunct to a paper which laws out the design in enough detail that we can understand precisely what is being depicted. Otherwise it could all be a con, smoke and mirrors that looks good to the uninformed eye but is no more realistic than the latest special effects in a Hollywood movie.

Mike Treder, CRN

Regarding Hal's comment, I obtained this response from Eric Drexler:

The dimer tool and its reaction energetics are, in fact, based on a quantum chemistry analysis in the March/April Journal of Computational and Theoretical Nanoscience, and the abstraction of hydrogen does not pull on the structure from which the hydrogen is being abstracted. It binds stably before, during, and after the reaction. Regarding a "fat fingers" problem in the multi-tip reactions from the Merkle paper, I gather that the commenter has not actually built molecular models and examined the relevant reaction geometries, or he would have seen that they have no such problem.

Tom Craver

Hal:

If the pyramidal tool tips were hollow, could another pyramid with a metal atom come up inside, altering the electric field on the tip?

This "Russian doll" stacking would, for that limited effect, get up to twice as many 'fingers' involved without occupying space in front of the tool tip carrying the carbons to the workpiece or abstracting hydrogen. It would alter the electric field of a tool tip without altering it's surface structure.

I'm not saying that's what the video showed, btw, and I really don't know the answer - would the weak electrical effects of the metal atom propagate enough through the tool tip to have a useful effect?

Tom Craver

I remember, years ago, asking a nano-discussion site how atoms would be forced to release from a tool-tip and bond to a workpiece.

The only response I got was one guy who suggested I go read a chemistry book. Apparently he thought the answer was so obvious I shouldn't be wasting people's time asking...

cdnprodigy

May be too simplistic a solution, but could the molecule to be deposited, be physically forced off of the tip with some sort of inert cylinder around the tip, moving to press against the molecule as the deposition location is reached?

jim moore

Mike-
I don't have ready access to the March/April Journal of Computational and Theoretical Nanoscience. Do you have any idea how reliable the new carbon dimer deposition tool would be? Robert Freitas' dimer deposition tool was not reliable enough.

Tom
At a minimum, in order for the deposition tool to work it has to be energetically favorable. You need to have a system of tool tip and surface that is higher in energy when the carbon dimer is attached to the tool and lower in energy when the dimer is on the surface and the tool tip is empty.

Hal
How do you recharge your hydrogen abstraction tool? Good question, (just one of the many devilish details that need to be worked out). One possible way to get rid of the hydrogen without falling into an infinite regression would be to heat up the tool. If the hydrogens attached to the tool tip are the least tightly bound atoms in the structure they would fly off first. Of course you would have to do that in a different chamber from the one you are making your diamond parts to avoid contamination.

Tom Craver

Jim

My other question above was "inspired" by the statement in Hal's writeup, that Merkle had suggested that "Bringing in some metal atoms and other large atoms can produce electric fields that change bonding strength of nearby atoms".

Since putting another tool with those metal atoms in front of the tooltip could get difficult in cramped spaces, I was wondering if the same approach could be applied from within the tool itself by moving metal atoms closer to or further from the inside of a hollow main tool's tip.

jim moore

Tom
I was giving you a bare bones answer to your "how atoms would be forced to release from a tool-tip and bond to a workpiece." question.

Mike Treder, CRN

Jim, I can't comment on the dimer deposition tool because it's beyond my level of technical expertise. Chris will probably want to say something about it, but he's traveling to Europe today, so it may be a little while. All I know is that he and Eric Drexler seemed quite impressed with the new model.

Tom Craver

Jim -

Well, I wasn't so much asking, as commenting on an attitude some people I've encountered have had, that it's an easy problem - just shove the atom in place and it'll bond and that's all there is to it and why don't we have this working already? I still don't have an in-depth understanding of the physics, but I did understand it about the level you described.

But yours was a good clear description - words to that effect should be included in any description of the idea of mechanosynthesis. Too often it's stated sort of like that old cartoon of two scientists standing at a blackboard: "The tool tip moves the atoms precisely into position (a here a miracle occurs) and the atoms bond to the workpiece."

Hal

The article Drexler points to is presumably this one, http://www.ingentaselect.com/rpsv/cw/asp/15461955/v2n1/s3/p45 . Unfortunately this journal is not available at the local research library and the article costs $49 to buy so I'm not going to try to follow up on it at this time. The deposition tool does sound promising, with a predicted failure rate of only 1 in 10^24; however, I gather that simulations have not yet been done of an actual deposition operation; in the case of the previous tool, those simulations showed a somewhat worse performance than the initial calculations had suggested.

I am very surprised by Drexler's claim that pulling a hydrogen atom off a molecule does not pull on the structure that the atom is attached to! That doesn't seem to make physical sense. The hydrogen is held to the carbon with considerable force, and even if you present a radical that it will bind to more readily, you should still have to overcome the force holding it to the carbon.

As far as the fat fingers, my point was that the movie lets us see the issues more concretely. Not only do the "fingers" have to come together, three of them in one of the reactions depicted, but also the "hands", i.e. the support structures, the belts and rollers and other ancillary equipment, have to have room as well. Clearly there are potential issues when we start to require many fingers at once. At a minimum the video graphically demonstrates the falsehood of claims that nanotech doesn't use fingers and that the fat finger issue is nonsensical. These reactants are held on support structures which must be positioned to bring them together with appropriate geometries. That is exactly what Smalley was talking about when he raised his fat-finger objection.

Chris Phoenix, CRN

Hal, you want to be careful with words like "falsehood." Smalley's "fat fingers" claim, as I understand it, is that each atom in the vicinity of the reaction will have to be moved through an independent trajectory by an independent mechanism. According to Kurzweil, Smalley said that 5 to 10 fingers would be necessary. (I can't find Smalley's article at the moment.) Three pyramidal supports moving through simple trajectories is not "Smalley fingers."

Questions and disagreements are fine, but it's starting to sound like you're more interested in attacking us than in talking with us. There are already a couple of people whose posts I don't even read. If you want to talk, make it constructive and civil.

Chris

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