Drexler viewed the synthesis of diamond not as a necessary step towards building nanofactories, but as a deliberately challenging test case. So the failure of diamond mechanosynthesis so far tells us little about the in-principle feasibility of Drexlerian nanofactories, and more about Drexler’s extreme optimism about practical blockers to nanotech. See the quote from Nanosystems below (emphasis mine).
Diamond is an important product in its own right, but here serves chiefly as a test case in exploring the feasibility of more general synthesis capabilities. [...]
Diamond has several advantages in this regard, as can be seen by a series of comparisons. Synthetic challenges often center around the framework of a molecule, and diamond is pure framework. In general, higher valence and participation in more rings makes an atom more difficult to bond correctly. At one extreme is hydrogen placement on a surface; at the other is the formation of multiple rings through tetravalent atoms. (Divalent and trivalent atoms such as oxygen and nitrogen are intermediate cases.) Solid silicon and germanium present the same topological challenges as diamond, but atoms lower in the periodic table are more readily subject to mechanochemical manipulation owing to their larger sizes and lower bond strengths and stiffnesses. Thus, a structure built entirely of rings of sp3 carbon atoms appears to maximize the basic challenges of bond formation, and diamond is such a structure. Further, diamond has the highest atom and covalent-bond density of any well-characterized material at ordinary pressures, maximizing problems of steric congestion.
He says Si and Ge surfaces would be easier to construct than diamond, and yet both theorists and experimentalists went straight for diamond. Surely the field should try hydrogen placement, then germanium, then silicon, then diamond? Drexler even opines in Nanosystems chapter 16 that diamondoid systems (fourth-generation nanofactories) will only be built by third-generation nanofactories made of things slightly weaker than diamondoid, which would have huge advantages over today’s crude tech but themselves sit at the end of a research program which I think would take humans $trillions to finish.
Drexler viewed the synthesis of diamond not as a necessary step towards building nanofactories, but as a deliberately challenging test case. So the failure of diamond mechanosynthesis so far tells us little about the in-principle feasibility of Drexlerian nanofactories, and more about Drexler’s extreme optimism about practical blockers to nanotech. See the quote from Nanosystems below (emphasis mine).
He says Si and Ge surfaces would be easier to construct than diamond, and yet both theorists and experimentalists went straight for diamond. Surely the field should try hydrogen placement, then germanium, then silicon, then diamond? Drexler even opines in Nanosystems chapter 16 that diamondoid systems (fourth-generation nanofactories) will only be built by third-generation nanofactories made of things slightly weaker than diamondoid, which would have huge advantages over today’s crude tech but themselves sit at the end of a research program which I think would take humans $trillions to finish.