It's often claimed that nanoscale engineering must be radically different from macroscale engineering, because "the normal laws of physics don't apply" or other such rhetoric.
It's true that some things are different at the nanoscale. Scaling laws describe boring (but still important) differences, like gravity becoming less important, motors becoming stronger, and processes becoming faster as devices shrink. Sometimes there are differences to be found in the behavior of electrons: an electron confined in a nanoscale particle may have different energy states, leading to things like glowing quantum dots. But this doesn't mean that everything is different.
Researchers were surprised to learn recently that nanoscale springs can behave pretty much as predicted by spring equations. According to this article, "'The results were surprising because they ran counter to the common wisdom in the literature,' said Colton."
I've never understood why it's assumed that everything must be different at the nanoscale. Large-scale mechanical behavior is just the aggregation of zillions of chemical bonds. Should things be that much different when only a few hundred bonds are involved? So different that not only the parameters, but the equations themselves change?
Can anyone (Hi, Richard!) point me at an example of the "common wisdom in the literature" that can explain why nanoscale springs would sproing substantially differently from larger springs?
It's worth pointing out that Drexler wrote in 1992: ".... at room temperature for rods with mechanical properties approximating those of bulk diamond. As can be seen, under these conditions, in the regime where shear and bending compliance are both important, quantum effects on positional uncertainty are minor for rods of nanometer or greater size ...." (Nanosystems 5.5.4, p. 110)
Obviously, the spring results reported above can't be generalized incautiously, and they don't prove that Drexler was right. But this is just the latest addition to a growing list of demonstrations that conventional wisdom about nanoscale systems can be wrong.
Drexler said that mechanical force could make precise chemistry happen on stiff crystalline surfaces. Conventional wisdom, extrapolating from biochemistry, said that crystal chemistry couldn't be that simple. Then a single silicon atom was removed from a crystal by an atomic force microscope and put back in the same place.
Drexler said that precise nanoscale parts could be frictionless. Conventional wisdom, extrapolating from (imprecise) MEMS, said that friction would increase with decreasing size. Then superlubricity was demonstrated.
In this case, the conventional wisdom extrapolated from electronic properties in systems with mobile electrons to mechanical properties in systems with relatively simple electronics. And again, the conventional wisdom has proven to be limited.
Such results should help to break the "he said/she said" logjam between Drexler and the theoretical physicists and chemists. Until now, it's been OK to ignore Drexler's calculations because they violated the conventional wisdom. But now that experiment has also violated the conventional wisdom in several key areas, it's time for skeptical scientists to match Drexler's calculations with calculations of their own. If they cannot, then they -- and the rest of us -- should start thinking about what it would mean if Drexler wasn't crazy after all, and exponential manufacturing of diamond-strength products with a time constant of hours really is possible.