Stick-n-place assembly

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

Context: Assembly of Crystolecules

One can make good use of this stickiness in the assembly of crystolecules.
End effectors do not need to have complex gripper shapes to do from closure.
a simple concave corner can suffice.

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
to get a bit more sticking force than mere vdW attraction.
Parts are moved but some sparse covalent bonds to the end-effector are formed and broken.
Note though that vdW forces are suprpisingly strong and
that sparse pinned covalent connection are sparse as the name implies.
So the binding strength is not all that far apart.
Especially when attractive keesome forces add are parrt of the vdW forces.
See Intercrystolecular forces & Intercrystolecular levitation
(the latter covers the repulsive case of Keesom forces)

Dense covalent carrying

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

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

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

Using surface commensurate interdigitation for indexing positions

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

Context: Mechanosynthesis

Again the stickiness is nit a problem but useful here too.
Atoms always stay bond to some tool or the target surface.
There are several ways to predictable transfers.

• 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"
and thus make for a non-energy-conservative situation.
I.e. going aroind inta a spacial (and tool orientational) cycle
does not necessarily mean ening up at the same nanoscale system system energy as
some energy may be pumped in from the SPM needle tip dive or or extracted ou tthat way.

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 Warning! you are moving into more speculative areas. (for slow efficiency optimizing systems) even expend just the absolute minimum amount of energy
to make sure the system always reliably runs forward and never backwards (defining and arrow of time
by dissipating energy by increasing the number of phase space microstates.
Thereby potenially vastly exceeding the fundamental limits of efficiency of in natural biological systems.
See page: Friction in diffusion transport for some thoughts on what the limits are there.

Misc

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

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

Related

• Early diamondoid nanosystem pixel (direct path)
• Replication backpack
• Strained shell crystolecule structure
• Seamless covalent cleaving