Re: Smalley's Objection to MNT feasibility

Forrest Bishop (
Thu, 11 Dec 1997 00:54:49 -0800

Eugene Leitl wrote:
> On Mon, 8 Dec 1997 DOUG.BAILEY@EY.COM wrote:
> > His problem is with thermal resolution and can be found at
> >
> I've just skimmed the article. His objection is not with the thermal noise
> (which is adressed by cooling down the device) or positional accuracy
> (which is not addressed as easily, for I cannot make a dynamics analysis
> as there is no definite manipulator structure yet) but a control problem.
> Too many things moving in too many direction over a surrealistic potential..
> Merkle says it is not a problem at all, since he has computer models which
> prove otherwise. Intuitively, he might be right -- I do not buy the
> corrugatedness of the energetic landscape when it cames to rigidly held
> radical tools.
> Merkle's newest (afaik) browsable paper can be found
> Where I do see problems, is the aforementioned positional accuracy (+- 10
> pm should be plenty, but +-100 pm is imo too much),

Sub-picometer (.6 pm) resolution has already been attained with
(visible light, BTW) techniques. These methods should be relatively
easily extensible
to 3D, and to positioning two separate objects using two or more probe
Granted, the reflectors are several dozens or hundreds of atomic
diameters away from
the desired reaction site, but cryo temps should remove this objection.

c.f. NASA Tech Briefs, Nov. 1997 at:

go to "TSP, Electronics, November,
"Heterodyne interferometers for subpicometer metrology"
"Bingo" no.

> sterical hindrance of
> reaction sites on diamondoid terraces,

Isn't this addressed well enough by the assembly sequence? Don't let a
become more than one or a few atoms high when a structure (atom) still
needs to
be added to the base of the terrace. I don't think this would be
restrictive on the structure class size (and I've built a non-trivial
of things).

>high surface contaminant
> concentration at cryogenic UHV conditions


> and associated radical
> lifetimes, sterical hindrance at the tip tool (a hollow tip may be best),
> which would make multiple tip reactions impossible, etc. etc. The possibly
> worst problem is the bootstrap problem. We can see Hy Brazeal from here,
> right behind the mist bank, but the ocean between us is studded with shark
> fins.

If it were easy, it wouldn't be any fun. ;)

> It is a nightmare of seemingly trivial details, but then God is in the
> details as John C. uses to say. If one is unwilling to call these
> constraints physical laws, one can call them technical difficulties.
> Whatever one may call them, if they are severe enough, machine-phase
> autoreplicators are dead meat. Or dead diamond. Whatever.
> > I'd appreciate anyone's informed opinion on Dr. Smalley's assertions.
> ciao,
> 'gene