4 ms·

See Drexler's mechanical nanotechnology from 1989.[1] There's a minimum size at which such mechanisms will work, and it's bigger than transistors. This won't s

See Drexler's mechanical nanotechnology from 1989.[1] There's a minimum size at which such mechanisms will work, and it's bigger than transistors. This won't scale down to single atoms, according to chemists. [1] http://www.nanoindustries.com/nanojbl/NanoConProc/nanocon2.html http://www.nanoindustries.com/nanojbl/NanoConProc/nanocon2.h...

kragen 2y ago
It seems like you've misremembered the situation somewhat. Merkle developed several of his families of mechanical logic, including this one, in order to answer some criticisms of Drexler's earliest mechanical nanotechnology proposals. Specifically: 1. Chemists were concerned that rod logic knobs touching each other would form chemical bonds and remain stuck together, rather than disengaging for the next clock cycle. (Macroscopic metal parts usually don't work this way, though "cold welding" is a thing, especially in space.) So this proposal‚ like some earlier ones like Merkle's buckling-spring logic, avoids any contact between unconnected parts of the mechanism, whether sliding or coming into and out of contact. 2. Someone calculated the power density of one of Drexler's early proposals and found that it exceeded the power density of high explosives during detonation, which obviously poses significant challenges for mechanism durability. You could just run them many orders of magnitude slower, but Merkle tackled the issue instead by designing reversible logic families which can dissipate arbitrarily little power per logic operation, only dissipating energy to erase stored bits. So, there's nothing preventing this kind of mechanism from scaling down to single atoms, and we already have working mechanisms like the atomic force microscope which demonstrate that even intermittent single-atom contact can work mechanically in just the way you'd expect it to from your macroscopic intuition. Moreover, the de Broglie wavelength of a baryon is enormously shorter than the de Broglie wavelength of an electron, so in fact mechanical logic (which works by moving around baryons) can scale down further than electronic logic, which is already running into Heisenberg problems with current semiconductor fabrication technology. Also, by the way, thanks to the work for which Boyer and Walker got part of the 01997 Nobel Prize in Chemistry, we probably know how ATP synthase works now, and it seems to work in a fairly similar way: https://www.youtube.com/watch?v=kXpzp4RDGJI https://www.youtube.com/watch?v=kXpzp4RDGJI
- zozbot234 2y ago
  The interesting question is how much energy is lost to mechanical friction for a single logic operation, and how this compares to static leakage losses in electronic circuits. It should also be noted that mechanical logic may turn out to be quite useful for specialized purposes as part of ordinary electronic devices, such as using nano-relay switches for power gating or as a kind of non-volatile memory.
  - kragen 2y ago
    That's one of many interesting questions, but avoiding it is why Merkle designed his reversible logic families in such a way that no mechanical friction is involved, because there is no sliding contact. There are still potentially other kinds of losses, though.
- floxy 2y ago
  >mechanical logic (which works by moving around baryons) can scale down further than electronic logic, which is already running into Heisenberg problems with current semiconductor fabrication technology. I think I must be missing something here, I thought this was working with atoms. Are you saying that someday mechanical logic could be made to work inside the nucleus? Seems like you might be limited to ~200 nucleons per atom, and then you'd have to transmit whatever data you computed outside the nucleus to the nucleus in the next atom over? Or are we talking about converting neutron stars into computing devices? Do you have a good source for further reading?
  - kragen 2y ago
    No, no, not at all! That kind of thing is very speculative, and I don't think anybody knows very much about it. What I'm saying is that the position of a nucleus is very, very much more precisely measurable than the position of an electron, so it has a much weaker tendency to tunnel to places you don't want it to be, causing computation errors. That allows you to store more bits in a given volume, and possibly do more computation in a given volume, if the entropy production mechanisms can be tamed. We routinely force electrons to tunnel through about ten nanometers of silicon dioxide to write to Flash memory (Fowler–Nordheim tunneling) using only on the order of 10–20 volts. That's about 60 atoms' worth of glass, and the position of each of those atoms is nailed down to only a tiny fraction of its bond length. So you can see that the positional uncertainty of the electrons is three or four orders of magnitude larger than the positional uncertainty of the atomic nuclei.
gene-h 2y ago
And why wouldn't it work? Linear slide like mechanisms consisting of a silver surface and single molecule have been demonstrated[0]. The molecule only moved along rows of the silver surface. It was demonstrated to stay in one of these grooves up to 150 nm. A huge distance at this scale. [0]https://www.osti.gov/servlets/purl/1767839 https://www.osti.gov/servlets/purl/1767839
- kragen 2y ago
  It can work (see my sibling comment) but it's tricky. The experiment you link was done under ultra-high vacuum and at low temperatures (below 7 K), using a quite exotic molecule which is, as I understand it, covered in halogens to combat the "sticky fingers" problem.
  - gradschool 2y ago
    You seem to be knowledgeable about this topic. The reversible component designs in the article appear to presuppose a clock signal without much else said about it. I get that someone might be able to prototype an individual gate, but is the implementation of a practical clock distribution network at molecular scales reasonable to take for granted?
    - kragen 2y ago
      I'm only acquainted with the basics of the topic, not really knowledgeable. It's an interesting question. I don't think the scale poses any problem—the smaller the scale is, the easier it is to distribute the clock—but there might be some interesting problems related to distributing the clock losslessly.
    - gsf_emergency 2y ago
      Not an expert, but would this count as molecular scale :)? https://en.wikipedia.org/wiki/Chemical_clock https://en.wikipedia.org/wiki/Chemical_clock (This version can be done at home with halides imho: https://en.wikipedia.org/wiki/Iodine_clock_reaction https://en.wikipedia.org/wiki/Iodine_clock_reaction) To your question: I suppose all you need is for the halide moieties (Br) in your gates to also couple to the halide ions (Br clock?). The experiment you link was conducted at 7K for the benefit of being able to observe it with STM?
7373737373 2y ago
I'd love to see a watch manufacturer try to build a watch-sized purely mechanical computer
- kragen 2y ago
  That's clearly feasible; the mechanical complexity for a mechanical computer is on the order of a Curta calculator, and I outlined some promising approaches to macroscopic mechanical digital logic 15 years ago in https://dercuano.github.io/notes/mechanical-computers.html https://dercuano.github.io/notes/mechanical-computers.html. Since then MEMS has advanced significantly and gone mainstream, and photolithographic and reactive-ion-etching-based silicon fabrication has been used for other purposes, including watchmaking, with macroscopic silicon flexure components going into first TAG Heuer's Guy Sémon's Zenith Oscillator in the Zenith Defy Lab https://www.hodinkee.com/articles/zenith-defy-lab-oscillator-introducing https://www.hodinkee.com/articles/zenith-defy-lab-oscillator... and then mainstream watches: https://wornandwound.com/no-escapement-an-overview-of-obtainable-watches-with-silicon-components/ https://wornandwound.com/no-escapement-an-overview-of-obtain... https://monochrome-watches.com/in-depth-the-future-of-silicon-hairspring-and-silicon-technology-in-watchmaking-with-expired-patent/ https://monochrome-watches.com/in-depth-the-future-of-silico... https://www.chrono24.com/magazine/innovative-escapements-from-silicon-to-microsystems-technology-p_97522/ https://www.chrono24.com/magazine/innovative-escapements-fro... (warning, GDPR mugging) https://www.azom.com/article.aspx?ArticleID=21921 https://www.azom.com/article.aspx?ArticleID=21921 https://www.europastar.com/the-watch-files/those-who-innovate/1004093197-silicon-the-gateway-to-the-future-of-mechanical.html https://www.europastar.com/the-watch-files/those-who-innovat...

kragen 2y ago

It seems like you've misremembered the situation somewhat. Merkle developed several of his families of mechanical logic, including this one, in order to answer some criticisms of Drexler's earliest mechanical nanotechnology proposals. Specifically: 1. Chemists were concerned that rod logic knobs touching each other would form chemical bonds and remain stuck together, rather than disengaging for the next clock cycle. (Macroscopic metal parts usually don't work this way, though "cold welding" is a thing, especially in space.) So this proposal‚ like some earlier ones like Merkle's buckling-spring logic, avoids any contact between unconnected parts of the mechanism, whether sliding or coming into and out of contact. 2. Someone calculated the power density of one of Drexler's early proposals and found that it exceeded the power density of high explosives during detonation, which obviously poses significant challenges for mechanism durability. You could just run them many orders of magnitude slower, but Merkle tackled the issue instead by designing reversible logic families which can dissipate arbitrarily little power per logic operation, only dissipating energy to erase stored bits. So, there's nothing preventing this kind of mechanism from scaling down to single atoms, and we already have working mechanisms like the atomic force microscope which demonstrate that even intermittent single-atom contact can work mechanically in just the way you'd expect it to from your macroscopic intuition. Moreover, the de Broglie wavelength of a baryon is enormously shorter than the de Broglie wavelength of an electron, so in fact mechanical logic (which works by moving around baryons) can scale down further than electronic logic, which is already running into Heisenberg problems with current semiconductor fabrication technology. Also, by the way, thanks to the work for which Boyer and Walker got part of the 01997 Nobel Prize in Chemistry, we probably know how ATP synthase works now, and it seems to work in a fairly similar way: https://www.youtube.com/watch?v=kXpzp4RDGJI https://www.youtube.com/watch?v=kXpzp4RDGJI

zozbot234 2y ago
The interesting question is how much energy is lost to mechanical friction for a single logic operation, and how this compares to static leakage losses in electronic circuits. It should also be noted that mechanical logic may turn out to be quite useful for specialized purposes as part of ordinary electronic devices, such as using nano-relay switches for power gating or as a kind of non-volatile memory.
- kragen 2y ago
  That's one of many interesting questions, but avoiding it is why Merkle designed his reversible logic families in such a way that no mechanical friction is involved, because there is no sliding contact. There are still potentially other kinds of losses, though.
floxy 2y ago
>mechanical logic (which works by moving around baryons) can scale down further than electronic logic, which is already running into Heisenberg problems with current semiconductor fabrication technology. I think I must be missing something here, I thought this was working with atoms. Are you saying that someday mechanical logic could be made to work inside the nucleus? Seems like you might be limited to ~200 nucleons per atom, and then you'd have to transmit whatever data you computed outside the nucleus to the nucleus in the next atom over? Or are we talking about converting neutron stars into computing devices? Do you have a good source for further reading?
- kragen 2y ago
  No, no, not at all! That kind of thing is very speculative, and I don't think anybody knows very much about it. What I'm saying is that the position of a nucleus is very, very much more precisely measurable than the position of an electron, so it has a much weaker tendency to tunnel to places you don't want it to be, causing computation errors. That allows you to store more bits in a given volume, and possibly do more computation in a given volume, if the entropy production mechanisms can be tamed. We routinely force electrons to tunnel through about ten nanometers of silicon dioxide to write to Flash memory (Fowler–Nordheim tunneling) using only on the order of 10–20 volts. That's about 60 atoms' worth of glass, and the position of each of those atoms is nailed down to only a tiny fraction of its bond length. So you can see that the positional uncertainty of the electrons is three or four orders of magnitude larger than the positional uncertainty of the atomic nuclei.

gene-h 2y ago

And why wouldn't it work? Linear slide like mechanisms consisting of a silver surface and single molecule have been demonstrated[0]. The molecule only moved along rows of the silver surface. It was demonstrated to stay in one of these grooves up to 150 nm. A huge distance at this scale. [0]https://www.osti.gov/servlets/purl/1767839 https://www.osti.gov/servlets/purl/1767839

kragen 2y ago
It can work (see my sibling comment) but it's tricky. The experiment you link was done under ultra-high vacuum and at low temperatures (below 7 K), using a quite exotic molecule which is, as I understand it, covered in halogens to combat the "sticky fingers" problem.
- gradschool 2y ago
  You seem to be knowledgeable about this topic. The reversible component designs in the article appear to presuppose a clock signal without much else said about it. I get that someone might be able to prototype an individual gate, but is the implementation of a practical clock distribution network at molecular scales reasonable to take for granted?
  - kragen 2y ago
    I'm only acquainted with the basics of the topic, not really knowledgeable. It's an interesting question. I don't think the scale poses any problem—the smaller the scale is, the easier it is to distribute the clock—but there might be some interesting problems related to distributing the clock losslessly.
  - gsf_emergency 2y ago
    Not an expert, but would this count as molecular scale :)? https://en.wikipedia.org/wiki/Chemical_clock https://en.wikipedia.org/wiki/Chemical_clock (This version can be done at home with halides imho: https://en.wikipedia.org/wiki/Iodine_clock_reaction https://en.wikipedia.org/wiki/Iodine_clock_reaction) To your question: I suppose all you need is for the halide moieties (Br) in your gates to also couple to the halide ions (Br clock?). The experiment you link was conducted at 7K for the benefit of being able to observe it with STM?

7373737373 2y ago

I'd love to see a watch manufacturer try to build a watch-sized purely mechanical computer

kragen 2y ago
That's clearly feasible; the mechanical complexity for a mechanical computer is on the order of a Curta calculator, and I outlined some promising approaches to macroscopic mechanical digital logic 15 years ago in https://dercuano.github.io/notes/mechanical-computers.html https://dercuano.github.io/notes/mechanical-computers.html. Since then MEMS has advanced significantly and gone mainstream, and photolithographic and reactive-ion-etching-based silicon fabrication has been used for other purposes, including watchmaking, with macroscopic silicon flexure components going into first TAG Heuer's Guy Sémon's Zenith Oscillator in the Zenith Defy Lab https://www.hodinkee.com/articles/zenith-defy-lab-oscillator-introducing https://www.hodinkee.com/articles/zenith-defy-lab-oscillator... and then mainstream watches: https://wornandwound.com/no-escapement-an-overview-of-obtainable-watches-with-silicon-components/ https://wornandwound.com/no-escapement-an-overview-of-obtain... https://monochrome-watches.com/in-depth-the-future-of-silicon-hairspring-and-silicon-technology-in-watchmaking-with-expired-patent/ https://monochrome-watches.com/in-depth-the-future-of-silico... https://www.chrono24.com/magazine/innovative-escapements-from-silicon-to-microsystems-technology-p_97522/ https://www.chrono24.com/magazine/innovative-escapements-fro... (warning, GDPR mugging) https://www.azom.com/article.aspx?ArticleID=21921 https://www.azom.com/article.aspx?ArticleID=21921 https://www.europastar.com/the-watch-files/those-who-innovate/1004093197-silicon-the-gateway-to-the-future-of-mechanical.html https://www.europastar.com/the-watch-files/those-who-innovat...