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« Setting Technology Priorities | Main | Hacking Nanotechnology »

March 14, 2006

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marko

Much more inofrmative with the voiceover. Now if only they could get the assistant to smile when holding up her new laptop, the professionalism would be complete!

Hal

This is a great improvement from the earlier version, especially in the later portions where the higher level assembly is going on.

I notice that they changed the early "mill" operation though. Previously they removed the two hydrogen atoms from the feedstock acetylene molecules separately. The second removal required the shielding effect of a metal atom as described in Merkle's "hydrogen metabolism" paper. Now, this all happens in one step - an abstraction tool swings down and presto, both hydrogens are hoovered away, while the carbons manage to be left behind.

I have always thought these manipulations looked unreasonable, because the atoms that remain behind must be held pretty firmly; but then they are easily removed when applied to the work piece. I wonder if there is any actual science behind these manipulations or if they are just an artist's dreamy conceptions.

I've also always wondered how the tool that abstracted away the two hydrogens gets rid of them. Wouldn't it need another tool that would take them off? But then, how does that tool get rid of them? Some people have suggested heat or electricity or something, but I don't know if there are any specific proposals to solve this. This is basically Smalley's "sticky fingers" problem (which some analysts claim does not exist).

One other point that is questionable is how the blocks stick together. The narrator implies that they simply have dangling bonds that hook up. In that case, how come the blocks were picked up so easily? Wouldn't they have tended to bond to what they were sitting on?

And then when they are placed, there will be hundreds or thousands of dangling bonds that are powerfully attracted to each other. Even assuming the surfaces are stable in an unterminated state, I can't help thinking that great quantities of energy will be liberated as the two surfaces are brought together, with possible reconstruction and dislocation. An analogy at the macroscopic scale would be to have surfaces with super-powerful magnets on them, which have to be brought together. It's easy to see how slight misalignments could occur as the surfaces slap together that last fraction of an inch.

All in all it is an entertaining video but I still think there are enormous scientific holes in it. It is far from clear that the processes depicted can really work. In that sense I think it is unfortunate to see it endorsed by the mechanosynthesis nanotech community; in the end if the video is discredited it could hurt the credibility of other, more carefully analyzed proposals.

Dino Fancellu

I think this may be it, on google video

video.google.com/videoplay?docid=-2022170440316254003&q=nanosystems

Saves you a big download

Chris Phoenix, CRN

Hal:

1) I've been told the reactions have been simulated.

2) The acetylene is held in place by a strained double bond; the H are held on by only a single bond. When the dimer is placed, it forms an unstrained double bond.

3) Regenerating tools has nothing to do with Smalley's sticky fingers. The H would eventually be added to O, or perhaps to more highly hydrogenated hydrocarbons (convert acetylene C2H2 into octane C8H18: Freitas's proposal).

4) Small terminated areas can be used to pick up the blocks (by Van der Waals force, very convenient at that scale if your manipulators are precise). Alignment pegs can be used to make sure the blocks are lined up before the dangling bonds meet. (Alignment pegs were suggested in Nanosystems. Are you familiar with Nanosystems?)

Any summary can be attacked for being too detailed or not detailed enough (sometimes both).

Chris

rami

same old drexler.
claiming to be the prophet of nanotecnology, he always demonstrate an utter lack of imagination. not only does drexler picture nanotechnology as machines based on hinges and levers, he also belive that what we will want to build with it is a laptop with a screen and bottons.

manish

nothing

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