View source for Programmable matter

{{short description|Matter which can change its physical properties in a programmable fashion}}
'''Programmable matter''' is [[matter]] which has the ability to change its physical properties (shape, density, [[Moduli (physics)|moduli]], conductivity, optical properties, etc.) in a programmable fashion, based upon user input or autonomous sensing.  Programmable matter is thus linked to the concept of a material which inherently has the ability to perform information processing.

== History ==
Programmable matter is a term originally coined in 1991 by [[Tommaso Toffoli|Toffoli]] and [[Norman Margolus|Margolus]] to refer to an ensemble of fine-grained computing elements arranged in space.<ref>{{Cite journal | last1 = Toffoli | first1 = Tommaso | author1-link = Tommaso Toffoli | last2 = Margolus | first2 = Norman | author2-link = Norman Margolus | title = Programmable matter: concepts and realization | journal = Physica D | volume = 47 | issue = 1–2 | pages = 263–272 | url = http://portal.acm.org/citation.cfm?id=104699.104736 | date = 1991 | doi = 10.1016/0167-2789(91)90296-L | bibcode = 1991PhyD...47..263T }}</ref>  Their paper describes a computing [[Substrate (materials science)|substrate]] that is composed of fine-grained compute nodes distributed throughout space which communicate using only nearest neighbor interactions.  In this context, programmable matter refers to compute models similar to [[cellular automata]] and [[lattice gas automata]].<ref>{{cite book | last1=Rothman | first1=D.H. | last2=Zaleski | first2 = S. | title=Lattice Gas Cellular Automata | publisher=Cambridge University Press | url=https://archive.org/details/latticegascellul0000roth | url-access=registration | orig-year = 1997|date=2004 | isbn = 9780521607605 }}</ref>  The CAM-8 architecture is an example hardware realization of this model.<ref>{{cite web|url=http://www.ai.mit.edu/projects/im/cam8/ |title=CAM8: a Parallel, Uniform, Scalable Architecture for Cellular Automata Experimentation |publisher=Ai.mit.edu |access-date=2013-04-10}}</ref>  This function is also known as "digital referenced areas" (DRA) in some forms of [[self-replicating machine]] science.<ref name=dra>[http://www.geocities.com/charles_c_22191/temporarypreviewfile.html?1205202563050 http://www.geocities.com/charles_c_22191/temporarypreviewfile.html?1205202563050] {{dead link|date=April 2017|bot=medic}}{{cbignore|bot=medic}}</ref>

In the early 1990s, there was a significant amount of work in reconfigurable modular robotics with a philosophy similar to programmable matter.<ref name=dra/>

As [[semiconductor]] technology, [[nanotechnology]], and self-replicating machine technology have advanced, the use of the term programmable matter has changed to reflect the fact that
it is possible to build an ensemble of elements which can be "programmed" to change their physical properties in reality, not just in [[simulation]].  Thus, programmable matter has come to mean "any bulk substance which can be programmed to change its physical properties."

In the summer of 1998, in a discussion on artificial atoms and programmable matter, [[Wil McCarthy]] and G. Snyder coined the term "quantum wellstone" (or simply "wellstone") to describe this hypothetical but plausible form of programmable matter.  McCarthy has used the term in his fiction.

In 2002, Seth Goldstein and Todd Mowry started the claytronics project at [[Carnegie Mellon University]] to investigate the underlying hardware and software mechanisms necessary to realize programmable matter.

In 2004, the [[DARPA]] Information Science and Technology group (ISAT) examined the potential of programmable matter.  This resulted in the 2005–2006 study "Realizing Programmable Matter", which laid out a multi-year program for the research and development of programmable matter.

In 2007, programmable matter was the subject of a DARPA research solicitation and subsequent program.<ref>{{cite web|url=http://www.darpa.mil/dso/solicitations/baa07-21mod9.html |title=DARPA research solicitation |url-status=dead |archive-url=https://web.archive.org/web/20090715100834/http://www.darpa.mil/dso/solicitations/baa07-21mod9.html |archive-date=July 15, 2009 }}</ref><ref>[http://www.darpa.mil/dso/thrusts/physci/newphys/program_matter/ DARPA Strategic Thrusts: Programmable Matter] {{webarchive |url=https://web.archive.org/web/20101212042616/http://www.darpa.mil/dso/thrusts/physci/newphys/program_matter/ |date=December 12, 2010 }}</ref>

From 2016 to 2022, the [[Agence nationale de la recherche|ANR]] has funded several research programs coordinated by Julien Bourgeois and Benoit Piranda at the [[FEMTO-ST Institute]], which is taking the lead in the Claytronics project initiated by Intel and Carnegie Mellon University.<ref>{{cite web|title=Hardware and software for creating programmable matter – ProgrammableMatter |website= anr.fr |url=https://anr.fr/Project-ANR-16-CE33-0022}}</ref>

== Approaches ==
[[File:Adaptnetic Structures.webm|thumb|A 'simple' programmable matter where the programmable element is external to the material itself. Magnetized non-Newtonian fluid, forming support columns which resist impacts and sudden pressure.]] In one school of thought, the programming could be external to the material and might be achieved by the "application of light, voltage, electric or magnetic fields, etc."  {{harv|McCarthy|2006}}. For example, a [[liquid crystal display]] is a form of programmable matter.  A second school of thought is that the individual units of the ensemble can compute and the result of their computation is a change in the ensemble's physical properties.  An example of this more ambitious form of programmable matter is claytronics.
 
There are many proposed implementations of programmable matter.  Scale is one key differentiator between different forms of programmable matter. At one end of the spectrum, reconfigurable modular robotics pursues a form of programmable matter where the individual units are in the centimeter size range.<ref name="dra" /><ref>[http://groups.csail.mit.edu/drl/research.html Research<!-- Bot generated title -->]</ref><ref>{{cite web |url=http://www.robotics.upenn.edu/people/yim.html |title=Mark Yim - GRASP Lab @ Penn |website=www.robotics.upenn.edu |access-date=17 January 2022 |archive-url=https://web.archive.org/web/20051116051221/http://www.robotics.upenn.edu/people/yim.html |archive-date=16 November 2005 |url-status=dead}}</ref>
At the nanoscale end of the spectrum, there are a tremendous number of different bases for programmable matter, ranging from shape changing molecules<ref name="stoddart.chem.ucla">{{cite web |url=http://stoddart.chem.ucla.edu/ |archive-url=https://web.archive.org/web/20041012001534/http://stoddart.chem.ucla.edu/ |url-status=dead |archive-date=2004-10-12 |title=UCLA Chemistry and Biochemistry |publisher=Stoddart.chem.ucla.edu |access-date=2013-04-10 }}</ref> to [[quantum dot]]s.  Quantum dots are in fact often referred to as artificial atoms.  In the micrometer to sub-millimeter range examples include [[Microelectromechanical systems|MEMS]]-based units, cells created using [[synthetic biology]], and the [[utility fog]] concept.

An important sub-group of programmable matter are [[robotic materials]], which combine the structural aspects of a composite with the affordances offered by tight integration of sensors, actuators, computation, and communication,<ref name="McEvoy Correll 2015 p. ">{{cite journal | last1=McEvoy | first1=M. A. | last2=Correll | first2=N. | title=Materials that couple sensing, actuation, computation, and communication | journal=Science | publisher=American Association for the Advancement of Science (AAAS) | volume=347 | issue=6228 | date=2015-03-20 | issn=0036-8075 | doi=10.1126/science.1261689| pmid=25792332 | s2cid=206563151 | doi-access=free }}</ref> while foregoing reconfiguration by particle motion.

== Examples  ==
There are many conceptions of programmable matter, and thus many discrete avenues of research using the name.  Below are some specific examples of programmable matter.

=== "Solid-liquid phase-change pumping" ===
Shape-changing and locomotion of solid objects are possible with solid-liquid phase change pumping.<ref name="solid-liquid phase change pumping">{{cite journal
|last1=Kaya
|first1=Kerem
|last2= Kravchenko
|first2=Alexander
|last3= Scarpellini
|first3=Claudia
|last4=Iseri
|first4=Emre 
|last5= Kragic
|first5=Danica
|last6= van der Wijngaart
|first6=Wouter
|doi =10.1002/adfm.202307105
|url =https://doi.org/10.1002/adfm.202307105
|journal = Advanced Functional Materials
|title = Programmable Matter with Free and High-Resolution Transfiguration and Locomotion
|date = 2023
|doi-access=free
}}</ref> This approach allows deforming objects into any intended shape with sub-millimetre resolution and freely changing their topology.

=== "Simple" ===
These include materials that can change their properties based on some input, but do not have the ability to do complex computation by themselves.

====Complex fluids====
{{main|Complex fluids}}
The physical properties of several complex fluids can be modified by applying a current or voltage, as is the case with [[liquid crystals]].

====Metamaterials====
{{main|Metamaterials}}
Metamaterials are artificial [[Composite material|composites]] that can be controlled to react in ways that do not occur in nature.  One example developed by David Smith and then by John Pendry and David Schuri is of a material that can have its [[index of refraction]] tuned so that it can have a different index of refraction at different points in the material. If tuned properly, this could result in an [[Cloaking device|invisibility cloak]].

A further example of programmable -mechanical- metamaterial is presented by Bergamini et al.<ref name="adaptive phononic crystal">{{cite journal
|last1=Bergamini
|first1=Andrea
|last2= Delpero
|first2=Tommaso
|last3= De Simoni
|first3=Luca
|last4=Di Lillo
|first4=Luigi 
|last5= Ruzzene
|first5=Massimo
|last6= Ermanni
|first6=Paolo
|doi =10.1002/adma.201305280
|issn =0935-9648
|journal = Advanced Materials
|number = 9
|pages = 1343–1347
|title = Phononic Crystal with Adaptive Connectivity
|volume = 2
|date = 2014
|pmid=24734298
|s2cid=23402889
}}</ref> Here, a pass band within the phononic bandgap is introduced, by exploiting variable stiffness of piezoelectric elements linking aluminum stubs to the aluminum plate to create a phononic crystal as in the work of Wu et al.<ref>{{cite journal
|last1=Wu
|first1=Tsung-Tsong
|last2= Huang
|first2=Zi-Gui 
|last3= Tsai 
|first3=Tzu-Chin 
|last4= Wu
|first4=Tzung-Chen
|doi =10.1063/1.2970992
|issn =0003-6951
|journal = Applied Physics Letters
|number = 11
|page = 111902
|title =Evidence of complete band gap and resonances in a plate with periodic stubbed surface
|volume = 93
|date = 2008
|bibcode=2008ApPhL..93k1902W
|url=http://ntur.lib.ntu.edu.tw//handle/246246/120241
}}
</ref> The piezoelectric elements are shunted to ground over synthetic inductors. Around the resonance frequency of the LC circuit formed by the piezoelectric and the inductors, the piezoelectric elements exhibit near zero stiffness, thus effectively disconnecting the stubs from the plate. This is considered an example of programmable mechanical metamaterial.<ref name="adaptive phononic crystal"/>

In 2021, Chen et al. demonstrated a mechanical metamaterial whose unit cells can each store a binary digit analogous to a bit inside a hard disk drive.<ref name="reprogrammable mechanical metamaterial">{{cite journal
|last1=Chen
|first1=Tian
|last2= Pauly
|first2=Mark
|last3= Reis M.
|first3=Pedro
|doi =10.1038/s41586-020-03123-5
|issn =1476-4687
|journal = Nature
|number =7842
|pages = 386–390
|title = A reprogrammable mechanical metamaterial with stable memory
|volume = 589
|date = 2021
|pmid=33473228
|bibcode=2021Natur.589..386C
|s2cid=231665050
}}</ref> Similarly, these mechanical unit cells are programmed through the interaction between two electromagnetic coils in the Maxwell configuration, and an embedded magnetorheological elastomer. Different binary states are associated with different stress-strain response of the material.

====Shape-changing molecules====
An active area of research is in molecules that can change their shape, as well as other properties, in response to external stimuli.  These molecules can be used individually or en masse to form new kinds of materials.  For example, [[James Fraser Stoddart|J Fraser Stoddart]]'s group at UCLA has been developing molecules that can change their electrical properties.<ref name="stoddart.chem.ucla" />

====Electropermanent magnets====
{{main|Electropermanent magnet}}
An electropermanent magnet is a type of [[magnet]] which consists of both an [[electromagnet]] and a dual material [[permanent magnet]], in which the [[magnetic field]] produced by the electromagnet is used to change the magnetization of the permanent magnet. The permanent magnet consists of magnetically hard and soft materials, of which only the soft material can have its magnetization changed. When the magnetically soft and hard materials have opposite magnetizations the magnet has no net field, and when they are aligned the magnet displays magnetic behaviour.<ref name=":0" />

They allow creating controllable permanent magnets where the magnetic effect can be maintained without requiring a continuous supply of electrical energy. For these reasons, electropermanent magnets are essential components of the research studies aiming to build programmable magnets that can give rise to self-building structures.<ref name=":0">{{cite web
  | last = Deyle
  | first = Travis
  | title = Electropermanent Magnets: Programmable Magnets with Zero Static Power Consumption Enable Smallest Modular Robots Yet
  | publisher = HiZook
  | date = 2010
  | url = http://www.hizook.com/blog/2010/12/07/electropermanent-magnets-programmable-magnets-zero-static-power-consumption-enable-s
  | access-date = 2012-04-06}}</ref><ref>{{cite web
  | last = Hardesty
  | first = Larry
  | title = Self-sculpting sand
  | publisher = MIT
  | date = 2012
  | url = http://web.mit.edu/newsoffice/2012/smart-robotic-sand-0402.html
  | access-date = 2012-04-06}}</ref>

=== Robotics-based approaches ===

====Self-reconfiguring modular robotics====
{{main|Self-reconfiguring modular robot}}
Self-reconfiguring modular robotics involves a group of basic robot modules working together to dynamically form shapes and create behaviours suitable for many tasks, similar to programmable matter. SRCMR aims to offer significant improvement to many kinds of objects or systems by introducing many new possibilities. For example: 1. Most important is the incredible flexibility that comes from the ability to change the physical structure and behavior of a solution by changing the software that controls modules. 2. The ability to self-repair by automatically replacing a broken module will make SRCMR solution incredibly resilient. 3. Reducing the environmental footprint by reusing the same modules in many different solutions. Self-reconfiguring modular robotics enjoys a vibrant and active research community.<ref>{{harv|Yim|Shen|Salemi|Rus|2007|pp=43–52}} An overview of recent work and challenges</ref>

====Claytronics====
Claytronics is an emerging field of [[engineering]] concerning reconfigurable [[Nanoscopic scale|nanoscale]] [[robot]]s ('claytronic [[atoms]]', or ''catoms'') designed to form much larger scale [[machines]] or mechanisms.  The catoms will be sub-millimeter computers that will eventually have the ability to move around, communicate with other computers, change color, and [[electrostatic]]ally connect to other catoms to form different shapes.

====Cellular automata====
{{main|Cellular automata}}
Cellular automata are a useful concept to abstract some of the concepts of discrete units interacting to give a desired overall behavior.

=== Quantum wells ===
{{main|Quantum well}}
Quantum wells can hold one or more electrons. Those electrons behave like [[artificial atom]]s which, like real atoms, can form [[covalent bonds]], but these are extremely weak. Because of their larger sizes, other properties are also widely different.

=== Synthetic biology ===
{{main|Synthetic biology}}
[[Image:Protein translation.gif|thumb|300px| A [[ribosome]] is a [[biological machine]] that utilizes [[protein dynamics]] on [[Nanoscopic scale|nanoscale]]s to synthesize [[proteins]].]]
Synthetic biology is a field that aims to engineer cells with "novel biological functions."{{citation needed|date=April 2019}}  Such [[Cell (biology)|cells]] are usually used to create larger systems (e.g., [[biofilms]]) which can be "programmed" utilizing synthetic [[gene networks]] such as [[James Collins (bioengineer)|genetic toggle switches]], to change their color, shape, etc. Such bioinspired approaches to materials production has been demonstrated, using self-assembling bacterial biofilm materials that can be programmed for specific functions, such as substrate adhesion, [[nanoparticle]] templating, and protein immobilization.<ref>{{cite journal|last1=Nguyen|first1=Peter|title=Programmable biofilm-based materials from engineered curli nanofibres|journal=Nature Communications|date=Sep 17, 2014|volume=5|page=4945|doi=10.1038/ncomms5945|pmid=25229329|bibcode=2014NatCo...5.4945N|doi-access=free}}</ref>

== See also ==
{{Portal|Science|Technology}}

* [[Computronium]]
* [[Nanotechnology]]
* [[Self-assembly]]
* [[Smart material]]
* [[Smartdust]]
* [[Ubiquitous computing]]
* [[Universal Turing machine]]
* [[Utility fog]]

== References ==
{{Reflist|30em}}

==Further reading==
{{refbegin}}
* {{Cite journal | doi=10.1109/MC.2005.198 | title=Programmable Matter | journal=IEEE Computer | last1=Goldstein | first1=Seth Copen | last2=Campbell | first2=Jason | last3 = Mowry | first3 = Todd C. | volume=38 | issue=6 | pages=99–101 | url=http://portal.acm.org/citation.cfm?id=1069668 | date = June 2005 | s2cid=17346523 }} 
* {{cite journal | last = McCarthy | first = Wil | title = Programmable Matter FAQ | journal = Nature | url = http://www.programmablematter.com/FAQ.html#A1 | date = 2006 | volume = 407 | issue = 6804 | page = 569 | doi = 10.1038/35036656 | pmid = 11034188 | s2cid = 5242445 | doi-access = free }} 
* {{Cite book | last = McCarthy | first = Wil | title = Hacking Matter: Levitating Chairs, Quantum Mirages, and the Infinite Weirdness of Programmable Atoms | isbn = 978-0-465-04428-3 | date = 2003 | publisher = Basic Books | location = New York | url = https://archive.org/details/hackingmatter00wilm | url-access = registration }} 
* {{Cite journal | doi = 10.1109/MRA.2007.339623 | title = Modular Self-Reconfigurable Robot Systems | journal = IEEE Robotics & Automation Magazine | date = March 2007 | page = 43 | volume = 14 | issue = 1 | last1 = Yim | first1 = Mark | last2 = Shen | first2 = Wei-Min | last3 = Salemi | first3 = Behnam | last4 = Rus | first4 = Daniela | last5 = Moll | first5 = Mark | last6 = Lipson | first6 = Hod | last7 = Klavins | first7 = Eric | last8 = Chirikjian | first8 = Gregory |author8-link=Gregory S. Chirikjian | s2cid = 11100988 | url = https://resolver.caltech.edu/CaltechAUTHORS:20100504-112342513 }}
*{{Cite journal |doi=10.1016/j.robot.2021.103875 | title=Engineering efficient and massively parallel 3D self-reconfiguration using sandboxing, scaffolding and coating | journal=Robotics and Autonomous Systems| last1=Thalamy| first1=Pierre | last2= Piranda| first2=Benoit| last3 = Bourgeois| first3 = Julien | volume=146 | issue=18 | pages=103875  | date = December 2021 | doi-access=free }} 
*{{Cite journal | title= Datom: A Deformable modular robot for building self-reconfigurable programmable matter |journal= 15th International Symposium on Distributed Autonomous Robotic Systems| last1= Piranda| first1=Benoit| last2 = Bourgeois| first2 = Julien | url=https://publiweb.femto-st.fr/tntnet/entries/17404/documents/author/data | date = 2021 |arxiv= 2005.03402}} 
{{refend}}

== External links ==
* {{cite news|title=DARPA (US Military) Programmable Matter Thrust| newspaper=Afcea International |date = 26 May 2009|url=http://www.afcea.org/content/?q=programmable-matter-research-solidifies}}
* {{cite web|title=The Programmable Matter Consortium|date= 20 April 2022|url=https://www.programmable-matter.com/}}

{{emerging technologies|topics=yes|robotics=yes|manufacture=yes|materials=yes}}

[[Category:Smart materials]]
[[Category:Articles containing video clips]]
[[Category:Robotics]]
[[Category:Synthetic biology]]