Re: Tip reactions... does Smalley have a point?

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Date: 29 Oct 2004 02:12:38 GMT

On 28 Oct 2004 18:50:25 GMT, lord_psi@hotmail.com (Jeremy) wrote:

>
>Last night, I was contemplating Smalley's fat-fingers/enzyme
>arguments, trying to follow his reasoning from the beginning. There
>is no question in my mind that diamond mechanosynthesis will work as
>advertized, but right now I'm looking at the fine motion controller.
>It's not made of diamond. There are a lot of other elements involved.
> In the process of constructing the fine motion controller, there are
>going to be times when a site is dehydrogenated immediately adjacent
>to a surface bound oxygen atom, or some other reactive moiety. Are
>the energetics such that such an oxygen atom won't move to the new
>site before the tip can bring in the new moiety that is supposed to go
>there? If that oxygen atom DOES move, and there are many similar
>examples from STM literature, then how do you prevent it from moving?
>Maybe with something like Smalley Fingers? Okay, an "Enzyme-like
>tool-tip" could work in place of Smalley fingers, but that's not going
>to be a simple piece of work. With sufficient mechanical energy, we
>shouldn't necessarily have to mimic enzymes ability to catalyze the
>reaction by binding to the transition state, but we still need
>stabilizing moieties surround the dedicated reaction tip without
>affecting the reaction. This is not a simple tip.
>
>This may already have been addressed, and if so, can I get some
>references? If not... are we arguing past Smalley and his ilk? Yes,
>diamond should work. But can we make an assembler out of only
>diamond? I would encourage the modelers out there to construct the
>fine motion controller step-by-step, or at least model the critical
>geometries, including flat surfaces, corners, and edges. Figure out
>the conditions necessary to keep less stable atoms where they belong
>when adjacent to active reaction sites. If we don't have to apply
>significant controls to the atoms surrounding the reaction sites, then
>we have a viable technology. If the necessary geometries are
>impossible... then Smalley may have a point.
>
>-Jeremy

I work with tomographic 3D atom probes, which *disassemble* things one
atom at a time. The samples have to be cooled to numbers like 20-40K,
because every time you remove one atom, the neighbors all want to move
around, and that messes up the structure you're trying to analyze. So
the assembly problem is similar: when the structure is partially
built, the damned critters don't want to stay where you finally want
them to be. This isn't like assembling tinker-toys.

John

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