Difference between revisions of "Connection method"
m |
(some cleanup) |
||
| Line 9: | Line 9: | ||
[Todo: Improve this article, add info-graphics] | [Todo: Improve this article, add info-graphics] | ||
| − | = Kinds of connection mechanisms | + | = Kinds of connection mechanisms dependent on scale = |
* single covalent bonds | * single covalent bonds | ||
| Line 18: | Line 18: | ||
['''Todo:''' add image] | ['''Todo:''' add image] | ||
| − | = Energy barrier locking (soft) = | + | = 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. <br> | In the macro-scale springs, magnets, gravitation, and almost unused electrostatic attraction belong to this class. <br> | ||
| Line 24: | Line 26: | ||
There thermal movement can knock a lock open by probabilistic chance which must be taken under consideration in system design. | 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] | + | 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. | All other locking methods do too display energy barriers but have other more predominant traits. | ||
| − | == Van der Waals locking == | + | === Van der Waals locking === |
Two coplanar atomically flat surfaces attract each other quite a lot. | Two coplanar atomically flat surfaces attract each other quite a lot. | ||
| − | * ~1nN per square nm this equates to around ~10,000 bar. <br> Original Source: (Nanosystems 9.7.1.) <br> indirect source: [http://www.nanomedicine.com/NMI/9.3.2.htm] (beware: the noted binding energy is | + | * ~1nN per square nm this equates to around ~10,000 bar. <br> Original Source: (Nanosystems 9.7.1.) <br> indirect source: [http://www.nanomedicine.com/NMI/9.3.2.htm] (beware: the noted binding energy is mistakenly taken from a covalent interface - Nanosystems 9.7.3.) <br> double indirect source: [http://www.jetpress.org/volume13/Nanofactory.htm#s3.2] |
* ~2.7nN per square Nm 1/20 the tensile strength of diamond <br> Source: (Nanosystems 3.5.1.b) (more than titanium and low grade steel) | * ~2.7nN per square Nm 1/20 the tensile strength of diamond <br> Source: (Nanosystems 3.5.1.b) (more than titanium and low grade steel) | ||
They can still slide effortlessly along each other (possibly [[superlubrication|superlubricating]]) so depending on the use indents may be needed to prevent that. ([[intuitive feel]]) | They can still slide effortlessly along each other (possibly [[superlubrication|superlubricating]]) so depending on the use indents may be needed to prevent that. ([[intuitive feel]]) | ||
| Line 40: | Line 42: | ||
Less manipulator complexity and less positioning [[atomic resolution|resolution]] (and thus stiffness) is needed. | Less manipulator complexity and less positioning [[atomic resolution|resolution]] (and thus stiffness) is needed. | ||
| − | For the tiniest assemblies counting only a handful atoms locking will be necessary since there are an | + | 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 | + | 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] | ['''todo:''' add image] | ||
| − | = Hierarchical locking = | + | == Hierarchical locking == |
Something is hierarchical locked when one has to remove a part such that a locking part can be removed. | 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. | The structure can be disassembled only in a specific order. | ||
| − | Hierarchically locked structures can have tree shaped | + | Hierarchically locked structures can have tree shaped typologies. |
If an energy barrier of the lower levels is overcome first it leads to a complete destruction of the structure. | If an energy barrier of the lower levels is overcome first it leads to a complete destruction of the structure. | ||
| Line 55: | Line 57: | ||
Example: [http://www.thingiverse.com/thing:200203 serial hierarchical locking structure] | Example: [http://www.thingiverse.com/thing:200203 serial hierarchical locking structure] | ||
| − | Interfaces could be hierarchically locked with sliding planes. [Todo: add | + | Interfaces could be hierarchically locked with sliding planes. [Todo: add info-sketch] |
---- | ---- | ||
| Line 65: | Line 67: | ||
Nails and screws base their locking ability on friction but in AP products one usually finds super-lubrication between surfaces. | Nails and screws base their locking ability on friction but in AP products one usually finds super-lubrication between surfaces. | ||
| − | One can design surfaces such that | + | 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 | + | 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 ( | + | 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:''' | + | Thus '''the classical nail and screw design probably makes no sense at the nanocosm''' ('''To investigate:''' in-how-far is this statement true?) |
= The locking nature of screws = | = The locking nature of screws = | ||
| Line 84: | Line 86: | ||
= Related = | = Related = | ||
| − | * Combination lock stones as a safety measure against malicious disassebly attacks are | + | * Combination lock stones as a safety measure against malicious disassebly attacks are mentioned [[Grey goo meme|here]]. |
= External references = | = External references = | ||
Revision as of 13:59, 9 April 2015
In the context of APM locking mechanisms are the simplest most compact physical structures that one can built that hold things together.
Reversible ones are needed to build recyclable AP systems and products.
They can be split into three classes:
- energy barrier locks
- hierarchical locks
- friction locks
[Todo: Improve this article, add info-graphics]
Contents
Kinds of connection mechanisms dependent on scale
- single covalent bonds
- surfaces full of open radicals
- reversible interlocking structures
- high level self aligning and dirt expulsing interfaces
[Todo: add image]
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
Two coplanar atomically flat surfaces attract each other quite a lot.
- ~1nN per square nm this equates to around ~10,000 bar.
Original Source: (Nanosystems 9.7.1.)
indirect source: [1] (beware: the noted binding energy is mistakenly taken from a covalent interface - Nanosystems 9.7.3.)
double indirect source: [2] - ~2.7nN per square Nm 1/20 the tensile strength of diamond
Source: (Nanosystems 3.5.1.b) (more than titanium and low grade steel)
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 resolution (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]
Hierarchical 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 typologies.
If an energy barrier of the lower levels is overcome first it leads to a complete destruction of the structure.
Example: serial hierarchical locking structure
Interfaces could be hierarchically locked with sliding planes. [Todo: add info-sketch]
Related: Expanding ridge joint
Friction
Nails and screws base their locking ability on friction but in AP products one usually finds super-lubrication between surfaces.
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?)
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)
- ...
Related
- Combination lock stones as a safety measure against malicious disassebly attacks are mentioned here.
External references
- further information: Nanosystems chapter 9.7 Adhesive interfaces
