Macroscale style machinery at the nanoscale

 Physics changes when one scales down things.
 This may pose serious problems.

If you are educated in physics and nanotechnology you will likely be quick to point out that this will not work because of the effects of one or more of the following scaling laws (here listed in informal form):

• rising surface area (per volume)
  >> concerns: rising friction; rising corrosion; clogging
• rising tendency towards thermodynamic equilibrium -- (Thermodynamics)
• rising influence of thermal motion -- (Jittery finger problem)
• rising influence of quantum mechanics
• falling available space (obviously) -- (Fat finger problem)
• falling material stiffness (less obvious) -- (Sloppy finger problem)
• rising influence of intermolecular forces -- (Sticky finger problem)
• rising effect of viscosity

But: All of these potential concerns have been analyzed.
The result: In total things change for the better rather than for the worse.
That is: For macroscale style machinery the changing of physics is actually an improving rather than a worsening.

Why nature doesn't do it this way albeit it being a better way is a topic different in kind. A concern not based on physically quantifiable scaling laws. See the main article: "Nature does it differently".

Limits to similarity

While superficially the targeted advanced productive nanosystems look very similar to macroscale machinery, looking just a bit deeper the similarities quickly start to end.

• Very different types of used materials (no metals but gemstones instead)
  preventing oxidation,
  preventing parts cold welding to others
  preventing eventual diffusion of easily slidehopping metal atoms
• More sturdy designs for the low material stiffness at small scales
  (designs that avoid mechanical ringing by electrical design principles)
• No usage of lubricants. They would only cause massive viscous drag.
• Operation at slower speeds. "Exploding" productivity at small scales allows that.
  (Note that this is about lower absolute speeds, not lower frequencies. Operation frequencies are way higher.)
• Means of assembly differing to the ones encountered at the macroscale
  E.g.: No usage of nuts and bolts (at least not in the classical sense where nuts and bolts are usually tiny compared to the linked parts and held in by friction)
• ...

High level considerations

It turns out that all the above mentioned common concerns:

• either do not hold at all under closer inspection
• or they are partially true but overcompensated by other less known factors

For detailed explanations regarding the individual concerns please follow the links above.
(wiki-TODO: complete those links)