Sub-picometer (.6 pm) resolution has already been attained with
interferometric
(visible light, BTW) techniques. These methods should be relatively
easily extensible
to 3D, and to positioning two separate objects using two or more probe
wavelengths.
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:
http://www.nasatech.com
go to "TSP, Electronics, November,
"Heterodyne interferometers for subpicometer metrology"
NPO-20046
"Bingo" no.
105
> sterical hindrance of
> reaction sites on diamondoid terraces,
Isn't this addressed well enough by the assembly sequence? Don't let a
terrace
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
particularly
restrictive on the structure class size (and I've built a non-trivial
number
of things).
>high surface contaminant
> concentration at cryogenic UHV conditions
huh?
> 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
Forrest