View source for Stick-n-place assembly

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At the nanoscale everything is "sticky" (See also related page: [[Sticky fingers problem]]). <br>
But this is actually more a feature than a problem as that stickiness holds everything nicely in place <br>
despite that at the nanoscale there is not really friction. <br>
Friction is replaced by energy barriers which essentially is <br>
the precise formal treatment of that informal stickiness. <br>

== Context: Assembly of [[Crystolecules]] ==

One can make good use of this stickiness in the assembly of [[crystolecule]]s. <br>
[[End effectors]] do not need to have complex gripper shapes to do [[from closure]]. <br>
a simple concave corner can suffice. <br>

Some things to look out for:
* [[Crystolecule newton's cradle]] … transmision of directed impulse (nonthermalized mchanical waves)
* [[Trapped charges in crystolecules]] … that could overpower vdW atraqction 
* [[Seamless covalent cleavage]] … vdW force sticking alone insufficient for preventing shoot-off and loss of the product crystolecule

=== Sparse covanlent pinning ===

For stick-n-place assembly one can covalently pin on several spots <br>
to get a bit more sticking force than mere vdW attraction. <br>
Parts are moved but some sparse covalent bonds to the end-effector are formed and broken. <br>
Note though that [[vdW force]]s are suprpisingly strong and <br>
that sparse pinned covalent connection are sparse as the name implies. <br>
So the binding strength is not all that far apart. <br>
Especially when attractive [[keesome force]]s add are parrt of the [[vdW force]]s. <br>
See [[Intercrystolecular forces]] & [[Intercrystolecular levitation]] <br>
(the latter covers the repulsive case of Keesom forces) <br>

=== Dense covalent carrying ===

In the extreme case it could be <br>
[[seamless covalent welding]] to the end-effector <br>
but with acute angle concave cleave-off notch <br>
And [[seamless covalent cleavage]] for getting it off again. <br>

Tough this is would  lead to unnecessary mechanical shocks causing … <br>
★ unnecessary energy dissipation and <br>
★ unnecessary requirements on over-engineering <br>
… so better to avoid. <br>

Better to just use <br>
★ [[seamless covalent cleavage]] for break-off of mechanosynthesis build-plates <br> 
★ [[seamless covalent welding]] for post assembly of larger crystolecules or bulk attached frames. <br>

=== Using surface commensurate interdigitation for indexing positions ===

See "notch snapping" on page: [[Intercrystolecular snapping modes]] <br>
This can be useful but also be a nasty source of off by one or more notched errors. <br>
So this might be a motivatnig factor to design for <br>
[[superlubric]] interfaces that are overpowered by [[vdW suck on]] ([[solid state surface tension]]) <br>
See page: [[Designing against Murphies law]] <br>

== Context: [[Mechanosynthesis]] ==

Again the stickiness is nit a problem but useful here too. <br>
Atoms always stay bond to some tool or the target surface. <br>
There are several ways to predictable transfers. <br>
* Thermodynamic downhill cascases (energetically wasteful and increasingly undesirable in later more advanced systems)
* bond topology (e.g. triply bonded but break the bonds one-by-one by according trajectory)
* trajectory dependent trasfer direction

For the last one: Exploit that [[SPM]] systems provide are "[[constant speed source and position control]]" <br>
and thus make for a non-energy-conservative situation. <br>
I.e. going aroind inta a spacial (and tool orientational) cycle <br>
does not necessarily mean ening up at the same nanoscale system system energy as <br>
some energy may be pumped in from the SPM needle tip dive or or extracted ou tthat way. <br>

=== Energy recuperation ===

Very advanced systems may even recuperate all that energy to externally (See: [[Mechanosynthesis energy recuperation]]). 

=== Towards the fundamental physical limits of efficiency ===

And {{speculaitivity warning}} (for slow efficiency optimizing systems) even expend just the absolute minimum amount of energy <br>
to make sure the system always reliably runs forward and never backwards (defining and [[arrow of time]] <br>
by dissipating energy by increasing the number of phase space microstates. <br>
Thereby potenially vastly exceeding the fundamental limits of efficiency of in natural biological systems. <br>
See page: [[Friction in diffusion transport]] for some thoughts on what the limits are there. <br>

== Misc ==

Stickiness in the form of eergy barriers is always present. <br>
To overcome such energy barriers one usually needs to actively design for it. <br> 
Highly relevant nanoengineering example: <br>
Incommensurate surfaces matchup based [[superlubricity]] allowing <br>
[[VdW suck-in and suck-on]] ([[solid state surface tension]]) to overpower the energy barriers (stickiness). <br>

Only in rare exotic cases one might loses energy barriers and stickiness in one or two dimensions of the three of 3D. <br>
[[superlubric]] remnant energy barriers that might be overcome by thermal motions. <br>
Potentially even leading to situations of zero static friction [[supercritical subperlubricity]]. <br>

== Related ==

* [[Early diamondoid nanosystem pixel]]
* [[Replication backpack]]
* [[Strained shell crystolecule structure]]
* [[Seamless covalent cleaving]]