View source for Assembly from atomically precise nanoscale and microscale parts

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[[File:Movie 30fps.gif|thumb|600px|right|Nanoscale specialized end-effector exploiting nanoscale physics (van der Waals sticking force) for not needing to resort to complex gripper mechnanisms. '''(CLICK IMAGE TO SEE ANIMATION)''']]

This is about assembly from smaller base parts (already bigger than atoms) 
to larger composite structures. Like e.g.:
* from [[crystolecules]] (see [[example crystolecules]]) <br>to  [[Crystolecular unit]]s <br> See: [[Assembly level 2 (gem-gum factory)]]
* from [[crystolecular unit]]s <br>to [[microcomponents]] <br> See: [[Assembly level 3 (gem-gum factory)]]

This page shall focus less on a particular size scale, <br>
and more on the relevant physical forces and design consequences in the context of assembly. <br>

= Relevant Nanoscale physics for assembly at smaller scales =

Related: [[Intercrystolecular forces]]

== Change of dominant forces ==

For part manipulation and assembly context: <br>
At the macroscale the dominant fundamental physical forces are:
* (1) unavoidably only downward directed gravity (excluding in space of course) and 
* (2) avoidably omnidirectional magnetic forces

At the nanoscale the dominant fundamental physical forces are instead:
* (1) unavoidably omnidirectional [[van der Waals force]]s (and avoidably electrostatic forces) and 
* (2) unavoidably omnidirectional thermal motions (to lesser degree) (also less of a "fundamental force")
 
== Van der Waals force replacing gravity in importance ==

The (mostly) attractive [[van der Waals force]]s between atomically precise flat surfaces … 
* … are very strong. While they are more than 100 times weaker than covalent forces, covalent forces are enormous, thus they are still huge. <br>
* … are proportional to surface area. 
* … would be strong at the macroscale too but one rarely encounters flat enough surfaces meeting each other.
* … are dominant over gravity due to down masses becoming so small relative to surface areas. Well known [[scaling law]].

Dominance of [[van der Waals force]]s means that everything sticks together. <br>
(Related but less applicable here due to already being bigger than atoms: [[Sticky finders problem]]) <br>

This [[van der Waals force]] sticking …
* can be exploited in assembly in various ways, in particular simplifying the end effectors for part manipulation.
* preventing random thermal motions jolts from making parts flying off (evaporate/sublimate like gas molecules)

For more details see main pages: <br>
[[Van der Waals force]] & [[nonbonded interactions]] <br>

== Change of relevant effects ==

Not fundamental forces, but highly relevant phenomena/principles/effects 
as holding methods and [[connection methods]] there is: 
* (1) [[Friction]] forces, these do not translate well to the nanoscale, conservatively better assume absence of it.
* (2) [[Form closure]] working perfectly totally scale invariantly across all scales.
* (3) Energy barriers by deformation (i.e. bending)
The last (3) latter combined with the preceding (2) gives sort of '''snap fit clip connectors'''. <br>
These should work well at the nanoscale with some energy efficiency caveats. <br>
(1) and (2) sort of blur. More on that later.

== stick-n-place ~vs~ pick-n-place ==

'''Grippers style end-effectors may be unnecessary and mostly redundant.''' 

Omnipresent omnidirectional attractive [[van der Waals force]] i.e. <br>
'''everything sticking to everything should be exploitable to <br> 
simplify the structural complexity of part manipulating endeffectors.''' <br>

What (sort of) replaces friction at the nanoscale is commensural interdigitation of atomic corrugation. <br>
So [[static friction]] at the macroscale (sort of) converts to a special case of [[form closure]] at the nanoscale. <br>
This does not constitute dynamic friction which is an other story that is … <br> 
… less relevant here in the context of parts assembly by end-effector and <br>
… more relevant in the context of moving bearings in the robotics behind the end-effector. <br>

=== pick-n-place – nanoscale physics abiding assembly ===

'''Macroscale:''' (Avoiding having magnets in all parts) <br>
one usually desires something like parallel acting grippers that feature: <br> 
– either sufficient friction to the gripped parts <br>
– or sufficient fully enclosing shape complementarity to the gripped parts. <br> 
'''What one inherits from naively copy pasting over to the nanoscale:'' <br>

Static friction related NEUTRAL/PRO: <br>
– Given static friction (sort of) becomes commensural interdigitation form closure <br>
an advantage of gripper style end effector design might be that <br>
'''pressing force can raise the corrugation energy barriers''' <br>
an thus exponentially reduce the likelihood of slipping due to [[accidental slip notch jumping]]. <br>

Static friction related NEUTRAL/CON: <br>
– Always the risk of one-off corrugation misgrippings. <br>
– Shoving the part all the way back may work for some parts. <br>
– parts with surfaces incommensurate to the grippers surfaces may be superlubric and be sucked back by [[van der Waals]] forces <br>

Undercutting form closure related CLEAR CONs: <br>
– A possibly non-trivial clasping motion is needed preferably keeping brackets parallel. <br>
– An undercut is needed to prevent slide-out of parts thus one gets stronger constraints on shape complementarity. <br>
– Form closure induced shape constraints distribute to the parts site and gripper style end-effectors side.<br>
– A larger number of standard gripper end-effectors may be needed. <br>

=== stick-n-place – nanoscale physics exploiting assembly ===

'''End-effector manipulators designed for exploiting nanoscale physics:''' 

[[Van der Waals force]] (and partial form closure) CLEAR PROs: <br>
– No clasping motion is needed, just a means to push off the stuck on parts is needed <br>
– Much weaker constraints on shape complementarity. No need for [[undercut]]s in shape complementary pickup. <br>

Static friction related: <br>
– Intentional design for superlubtic suck-up leading to reliable larger scale self centering <br>
… possibly less placement accuracy needed <br>


Static friction related NEUTRAL/CON: <br>
– For non-superlubcric cases: Always the risk of one-off corrugation misgrippings. <br>
– commensural interdigitation sticking might be weak to jolts from [[bending snaps]] <br>
and even thermal motions for the very smallest small surface contact areas and high temperatures <br>
– [[accidental slip notch jumping]] <br>

== Unintentional misplacements ==

Going down from the strongest and most likely pertorbation (shock) to the weakest and least likely. <br>
This qualitatively foruses on external influences not insuffieciencies in the driving robotics. At last not directly. <br>
 
[[Van der Waals force]] combined with commensural interdigitation causes static friction <br>
– energy barriers against sliding <br>
– force barriers against sliding <br>
Referred to as notches in the following. <br>

=== Slip-notch-jumps and even full-fly-off due to off-site snap induced shocks ===

Violent shocks from [[bending snaps]] acoustically transmitted elsewhere <br>
(and not yet fully thermalized) may not only lead to slips but even full fly-off. <br>

There are non-thermal shock motions but <br>
with thermal speeds (~ speed of sound) and larger amplitudes. See pages: <br>
* [[Bending snaps]]
* [[Accidental slip notch jumping]]

=== Slip-notch-jumps due to thermal motions (unclear) ===

But the energy barriers against sliding are much smaller tha the ones for full ripp-off <br>
and thus more amenable to be overcome by mere thermal motion energies. <br>
I.e. high temperatures may be able to supply sufficient energy to <br>
cause unintentional slips across commensural interdigitation energy barriers. <br>
Especially when nearing more incommensural cases with <br>
zero static friction as the limit in the case of [[superbubricity]]. <br>

=== Full-fly-off due to thermal motions (unlikely) ===

[[Van der Waals force]] more or less suppress thermal motion based undesired disassembly. <br>
Due to [[van der Waals force]] being so surprisingly strong <br>
even rather small contact areas already suffice to prevent a full separation fly-off event and that <br>
even at the highest temperatures materials can endure before decomposing/melting/… <br>

=== Small [[crystolecules]] ===

– Small parts feature small surfaces so binding energies can't be very high for these. Lower vdW sticking force. <br>
– Small parts can't have many atomic grooves and thus can't be very incommensural. Raising the (low) force against sliding a notch. <br>

= Summarizing hypothesis and related questions =

{{Todo|Prove / corroborate following hypothesis and answer subsequent questions.}}

'''Hypothesis:''' <br>
To do assembly of crystolecules <br>
one can rely on attractive [[van der Waals force]]s, <br>
thereby avoiding the complexity of grippers that <br>
constrain part position via undercutting form closure. <br>

❓Q: How big are binding energies and <br>
maximal attractive forces per area more precisely <br>
i.e. beyond existing models? <br>
=> [[Intercrystolecular interactions]]

❓Q: How likely do snaps yields undesired outcomes? <br>
Snaps of similar or greater energy to <br>
binding / "holding" energy. <br>
Misplacement / fly-off to stick elsewhere / … <br>
=> [[Intercrystolecular snapping modes]]

❓Q: What are the snapping modes? And … <br>
❓Q: In how far need can and need these <br>
snapping modes be avoided <br>
in crystolecule assembly? <br>
=> [[Intercrystolecular snapping modes]] <br>

❓Q: Are there furthe ropportunities? <br>
=> [[Intercrystolecular levitation]] <br>

= Related =

* '''[[Assembly level 2 (gem-gum factory)]]''' & [[Assembly level 3 (gem-gum factory)]]
* '''[[Crystolecule assembly robotics]]''' & [[Sequence of zones]]
* [[Intercrystolecular forces]], [[Nonbonded forces]], [[Nonbonded interactions]], [[Van der Waals force]]
* [[Connection method]]
----
* [[Intercrystolecular interactions]]
* [[Intercrystolecular snapping modes]]
* [[Intercrystolecular levitation]]

= External links =

* Snap fit

[[Category:Far term target]]