Depending on the size of the observed chunk of product one can find different kinds of connection mechanisms. On the biggest scale advanced self aligning and self cleaning interfaces are possible. On smaller scales down to the physical limit there can be found:
- interlocking structures
- surfaces perfectly matching the shape of their conter-faces sticking togetherby VdW force
- shape locking mechanisms
- and finally covalent bonds between atoms
the simplest most compact physical structures that one can built that hold things together.
To be able to do recycling efficiently and fast it is necessary to make the connection mechanisms at the smallest scales reversible. e.g. the energy stored in a snap connection must be gently recollected instead of being suddenly released in a "click" sound. If this is not done great amounts of waste heat are produced need to be removed.
Connection methods can be split into three classes:
- energy barrier locks
- hierarchical locks
- friction locks
(wiki-TODO: Improve this article, add info-graphics)
- 1 The different methods to lock building blocks into place
- 2 Kinds of connection mechanisms that are typical for a specific scale
- 3 The locking nature of screws
- 4 Examples for various combinations of locking types
- 5 Related
- 6 External references
The different methods to lock building blocks into place
Energy barrier locking (soft)
In the macro-scale springs, magnets, gravitation, and almost unused electrostatic attraction belong to this class.
In the nano-scale springs, VdW-force (Van der Walls attraction), chemical bonds and in some cases electrostatic attraction are well usable.
There thermal movement can knock a lock open by probabilistic chance which must be taken under consideration in system design. Energy barriers high enough to effectively prevent opening by chance can be easily reached. [Todo: add VdW math example; add more details]
All other locking methods do too display energy barriers but have other more predominant traits.
Van der Waals locking
Although two coplanar atomically flat surfaces attract each other quite a lot (Values and comparisons on the "Van der Waals force" page) they can still slide effortlessly along each other (possibly superlubricating) so depending on the use indents may be needed to prevent that. (intuitive feel)
Van der Waals forces can be used to do self assisted assembly (which is a weaker form of self assembly aka brownian assembly). When assembling a hinge one does not need to plug the axle in actively and fix it in place with e.g. a locking snap-ring. Instead the axle gets sucked in as soon as its hold over its sleeve. One gets it out again by pushing with a blunt tool. This simplifies assembly a lot. Less manipulator complexity and less positioning precision (and thus stiffness) is needed.
For the tiniest assemblies counting only a handful atoms locking will be necessary since there are an Avogadro number (~6*10^23) of parts so some will thermally self disassemble if the probability for this is extremely but not astronomically low. The probability P for thermal self disassemly of parts sicking together with energy E quickly becomes astronomically low as can be seen by the formula: P = e^-(E/(kT)).
[todo: add image]
Main article: Form locking
Something is hierarchical locked when one has to remove a part such that a locking part can be removed. The structure can be disassembled only in a specific order. Hierarchically locked structures can have tree shaped topologies.
Related: Expanding ridge joint
Nails and screws base their locking ability on friction but in advanced atomically precise products one usually finds super-lubrication between surfaces. Also thermal motion is regularly knocking everything loose.
One can design surfaces such that they perfectly intermesh but this would effectively create a series of energy barriers (energy barrier locking) in which the barrier after the first one won't have much use (linear instead of exponential decrease of accidental disassembly probability). Furthermore the energy might be not well recoverable (non-stiff hydrogen bonds dissipate power) leading to unnecessary waste heat. Thus the classical nail and screw design probably makes no sense at the nanocosm (To investigate: in-how-far is this statement true?)
Kinds of connection mechanisms that are typical for a specific scale
- <1nm - single covalent bonds
- <1nm...typical:32nm...<1µm -- matching surfaces full of open radicals (densely packed -> irreversible connection)
- >32nm...typical:1µm...open-end -- reversible interlocking structures
- >1µm...typical:1mm...open-end -- high level self aligning and dirt expulsing interfaces
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Reversible nanoscale connection methods that are useful at the microscale
Picture: A fir-tree connector piece. One of a pair.
- The identical partner part is not depicted.
- The supporting rail fir tree structures above are not depicted.
- The opposing fir tree structures below are not depicted.
Imagine a second identical part mirrored on the large green plane. Now when a simple cuboid shaped plate (the locking plate) is pushed down between the two still contacting green planes then both the the depicted and the not depicted parts move apart. They are guided by the up facing fir tree structures sliding in the not depicted supporting rails above. When the two parts move apart their down-facing long fir three profiles can interlock with opposing fir trees structures that are too not depicted here. Once the locking is complete the locking plate is held in place by VdW forces. In principle such a mechanism can be both bi-stable and reversible.
Fir tree structures are a desirable design decision since they can retain more of the total material strength than simple dovetail interlockings.
Structures like these are especially suitable for reversibly tying together microcomponents.
- (wiki-TODO: main article) Nanoscale connection method
Microscale connection methods used by humans at the macroscale
Main article: Macroscale active align-and-fuse connectors
With advanced gem-gum technology a method for connecting pieces (like e.g. pipe segments) could look like the following. First pieces (e.g. pipe segments) would be roughly aligned by hand. Then small machinery can take care of the remaining fine alignment. The auto-alignment does not need much energy. It could be driven by internal energy storage (whatever the charging method) or the energy from the manual alignment. A kind of ratchet like mechanism allowing only motion towards better alignment may be possible.
When the surfaces are separated and inactive the interlocking structures (like fir-tree-hooks) could be retracted and dirt-exclusion-ports closed such that only a flat surface is exposed that can slide. Electrostatic sensors can detect when a matching partner surface contacts triggering hook deployal.
Some gaps can be left such that some soft dirt can be tolerated in a closed connection. Advanced versions may even be capable of actively pushing out dirt for the interface.
The connectivity providing machinery could be in the microscale so still not visible to the human eye. Consecutive interfaces could lie very close together (again in the microscale) but the size of the separated chunks should be kept at least in the millimeter scale (See: splinter prevention). Choosing a non-default sub millimeter splitting location needs to be done via software somehow. Even part embedded software interfaces for the choice of a specific slice-location are thinkable. A (passive colored) touchscreen slider could be displayed magnifying the slice position.
One thing that regularly get's sliced open and patched up badly today (2017) are streets. Imagine this kind of technology in future upgraded street infrastructure.
Self alignment with macroscale conical shapes is obviously an option. It may simplify small scale machinery but limits allowed macroscale shapes.
The locking nature of screws
- mechanical advantage
- self-retention by friction
Examples for various combinations of locking types
- snap buckles: pure energy barrier locking - zero hierarchical levels
- snap ring: hierarchical locking of at least one but most of the time two layer
- door handle mechanism: hierarchical locking of one layer (with retention of the locking part)
- Adhesive interfaces like Van der Waals force, Seamless covalent welding, ionic and hydrogen bonding.
- Friction does not work well as a connection method at the nanoscale.
- Connection methods are of paramount importance for reconfigurable frame systems (e.g. see: ReChain frame systems)
- Combination lock stones as a safety measure against malicious disassembly attacks are mentioned here.
- further information: Nanosystems chapter 9.7 Adhesive interfaces