View source for Digital control over reversibly composable units of matter

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'''Digital control over matter''' or '''digital mattercontrol''' for short. <br>
Not to confuse with [[digital manufacturing]].

This does not mean digital control over manufacturing machinery. <br>
This does mean digital control over (recomposable) units of matter.

== Applicability to all scales ==

Why the generic wording "units of matter"? Because it applies both …
* to preproduced parts of suitable shape and
* to the smallest possible pieces of matter, indivitual atoms.

Benefits are gained in both cases. <br> 
This is not specific to [[atomic precision]].

== Digital means error correction ==

The main consequence of "digital" is <br>
the possibility and presence of error correction. <br>
This is what eventually will bring to the physical world <br>
what digitalization brought to the world of nonphysical information processing. <br>
A huge revolution.

So far it just has not happened yet due to parts being <br>
* to big to make practical products and 
* too expensive to mass produce.
Just like in the beginnings of the revolution that was the start of the information age.

More on error correction further down.

== Discrete pieces & pick-and-place (scale independent) ==

One very advanced form of digital control over matter is to have the capability <br>
to control the placement of individual atoms [[FAPP]] fully deterministically.  

But [[digital control over matter]] is also possible at the macroscale. <br>
Prerequisite for that is that there are pre-made <br>
standard building blocks that are reversibly recomposable. <br>
These building blocks can be pre-produced via various manufacturing methods <br>
including 3D-printing, casting, injection molding or whatever is feasible. <br>
Note that while the machines for the preproduction can and likely will be <br>
under digital control this is not [[digital control over matter]]. <br> 
What ''is'' [[digital control over matter]] is the subsequent <br> 
reversible pick and place assembly and recomposition of these pre-built parts.
 
Bits are structurally reversible (not necessarily energetically reversible). <br>
They can be discretely written and deleted. <br>
Digital control over matter thus needs to have its pieces discretely addable and removable. <br>

Actually due to the facts that …
* physical pieces cannot be magically deleted (or spawned) "POOF" and
* removal implies reversibe connection mechanisms
… digital control over matter implies an analogy not just to digital logic <br>
but to [[reversible logic|reversible digital logic]]. <br>
<small>(Side-note1: Reversible logic features the potential for energetic reversibility.)</small><br>
<small>(Side-note2: Note that immutability is compatible with reversibility as there is uncomputation in so called [[retractile cascades]].)</small><br>

See related page: [[Tracing trajectories of component in machine phase]]

== Error prevention ==

Self centering structures can help funneling parts to the places where they are supposed to go. <br>
Macroscopically without heavy vibrations there is a super exponential drop in error rate. <br> 
At some point the error rate is literally zero (dominated by other processes like robot breakdown).

At the nanoscale what represents the funneling in [[piezomechanosynthesis]] are the attractive spots on the crystal lattice. <br>
Relevant here for the error rates is the quantity of [[lattice scaled stiffness]].

=== Self-centering funnels to redirect entropy ===

Conceputually one can think of it like this: <br>
A system fully in machine phase has zero entropy. Everything is known. <br>
A placement mechanism has some placement error that "intends" to introduce some entropy into the system. <br>
The self centering funnel or crystal lattice point attraction restores the entropy to zero. <br>
Entropy can only grow. So where does the entropy go you ask? Sound and heat of course. <br>
Energetically this is not relevant at macroscale. <br>
The annoying clanking sound is though (clanking replicator). <br>
At the nanoscale the energetic loss will eventually become relevant though and <br>
is subject to optimization (see idea: [[Dissipation sharing]]). <br>
What one essentially does is pumping out the entropy to the impulse space <br>
before any of it can seep into position space. <br>
Related: [[Phase space]]

=== Optimization; minimization of loss of energy (dissipation) ===

Stiffer robotic structures and slower operation speeds give lower ingress of entropy per assembly step. [[accidentally suggestive|Less wiggle to funnel]].<br>
This lowers dissipation and allows (but does not necessitate) for smaller funneling structures or materials with lower [[lattice scaled stiffness]].<br>
Related to stiffer structures and funneling the wiggle: [[Combining advantages of different selfassembly technologies]]

== Error correction ==

Error rates in [[piezomechanosynthesis]] or bigger scale pick-and-place processes can be kept low by repeatedly testing results. <br> 
This can be as simple as by touch, not necessarily a need for cameras that wouldn't work at the nanoscale.

Repeated testing for correct assembly scales exponentially essentially allowing [[FAPP]] perfectly error free nanocomponents like [[crystolecules]] and [[microcomponents]]. <br>
pressing down the error rate that is already low to begin with due to other means.

Of course there is [[radiation damage]] at bigger scales. <br>
This can be taken by whole system redundancy and more advanced things like self repair <br>
(also strongly based on the digital control of matter foundation).

== What does digital mean concretely ==

In [[digital control over matter]] the base parts are digital in the sense that [[error correction]] applies. <br>
But not in the sense of a single bit per part. Rather in the sense of a set of bits for each part.
* Their positions are exactly known at all times ([[machine phase]]). E.g. via coordinates or connection topology.
* Their type within a finite discrete (but potentially large) set of options is exactly known. An ID.
* In [[gemstone based APM]] context: For each ID the geometry is known again in a digital way (bond topology)

== Link between digital mattercontrol and mechanical metamaterials ==

Having (due to [[machine phase]]) reversibly re-composable base is an excellent basis for metamaterials <br>
as properties are defined by structure and the structure can be reversibly recomposed.

== Relation to 3D printing ==

'''3D printing alone is not "digital control over matter"!'''<br>
It is one of many pre-producing processes that can make base parts for "digital control over matter".

The revolution in 3D printing is rather merely that 
* BIG: Materials needed for building the 3D-printer machines are cheap (initiated by RepRap self-replication!) aiding in local at home workshop access and a largely unnoticed Cambrian explosion of technological progress  
* BIG: Production processes are vastly simplified (no complex toolpaths and no toolchanges needed)
* MINOR: novel complex geometries became possible (this is rarely fully exploited) 
* MINOR: additive rather than subtractive meaning net-shape no waste chips <br>(many prints fail and are immediately disposed of, plus plastic is much less recyclable than metal)
* DETRIMENTAL: In place printing hype. See below …

=== Detrimental in place printing hype ===

Saving (manual) assembly effort by printing everything in one piece. <br>
'''In place printing of big monolithic parts deeply goes against "digital control over matter".''' <br>
There is nobreversible recomposability and potential for error correcting assembly. <br>

That beside adding additional design constraints like e.g. <br>
more overhang limitation, more layer strenght direction constraints, <br>
worse backlash in rolling or sliding interfaces, ...

Monolithic designs tend to more bespoke and less reusable <br>
due to unseperably combining functionality in special ways <br>
only suitable to specific application case. <br>

This is a recipe for creating waste. <br>
Especially for the more advanced context of <br>
undesirable [[in place mechanosynthesis]]. <br>
See: [[The crystolecular waste problem]]

== Delineation ==

* [[Digital manufacturing]] – usually just referring to digital control of machines that have analog control over matter

== Related ==

* [[Machine phase]]
* '''[[Simultaneous prototyping across scales]]''' & [[The three axes of the Center for Bits and Atoms]]
* [[materializable programs]], [[programmable materials]]
* [[Mobile robotic device]]
* [[The killer features of APM]]
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* [[Center for Bits and Atoms]]
* [[The three axes of the Center for Bits and Atoms]]
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* [[Common misconceptions]] – "Thermodynamics prevents one from having every atom at the place we want it" - wrong for practical scales
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* [[Error correction]]
* ?? parity bits and more complicated redundancy schemes ??
* Shannon information theory
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* [[Gemstone based metamaterial]]s, [[mechanical metamaterial]]s, [[metamaterial]]s, ([[Low level gemstone metamaterial]])
* [[Reversible logic]]
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* Digital control over matter despite mere [[topological atomic precision]] and lack of per atom [[positional control]]. <br>See: [[Robo approach]] in the context of the [[incremental path]]

[[Category:Programming]]
[[Category:Software]]