Rising surface area per volume of smaller machinery parts
A well known scaling law with some availability bias of over other lesser known scaling laws
that need to be looked at too to get the full picture.
Consequences & counters
★ Higher surface available for chemical reactions; higher catalytic activity; see page: Oxidation countered by
– sealing of the sensitive interior (fruit interior analogy) &
– picking the right non-reactive stiff for the exterior e.g. by H of F passivated diamond (see: Atomically precise surface passivation)
★ Higher bearing surface area of smaller machinery countered by
– higher throughput of smaller machinery and
– the paradoxically seeming approach of Increasing bearing area to decrease friction
★ Less effective thermal insulation of smaller machinery
– Don't do mechanosynthesis in free floating nanobots. This is a bad idea for many other reasons not only including safety.
★ More difficult cooling of bigger machinery (equivalently to the preceding just the flipped viewpoint)
– Be aware of limits of power density imposed by limits of cooling,
… the absurdly high seeming values for power density stated in the book Nanosystems
… do not take cooling into account (so meant but not well and clear stated).
… These values do only hold for systems so small that they are still steady state coolable
… exclusive or short bursts in bulk where the thermal capacity can take the waste heat without thermal damage.
This scaling law as major source of criticism towards proposed macroscale style machinery at the nanoscale
This well known scaling law and its consequences is one of the most predictably upcoming
criticisms towards the idea of macroscale style machinery at the nanoscale.
But the here mentioned counters are rarely seen as these come from …
★ lesser known scaling laws
★ assumptions based on current day experimental capability limits
– e.g. limited sealing against rest gasses in UHV,
– FAPP perfect vacuum PPV not yet achievable due to chamber volume smallness and sealing quality and surface quality limits)
Related
- Bigger surface area of smaller machinery … more redundant page
- Twice the surface area of half the volume … somewhat redundant page
- Scaling laws
- Macroscale style machinery at the nanoscale
- Oxidation
External links
- Square–cube law
- Allometry – (related: Tree allometry)
- Surface-area-to-volume ratio – (related: Allen's_rule)
- Kleiber's law – metabolic rate of animals over mass – (related: Metabolic theory of ecology)