A chemical computer, also called a reaction-diffusion computer, Belousov–Zhabotinsky (BZ) computer, or gooware computer, is an unconventional computer based on a semi-solid chemical "soup" where data are represented by varying concentrations of chemicals. The computations are performed by naturally occurring

chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking ...

Background

Originally chemical reactions were seen as a simple move towards a stable equilibrium which was not very promising for computation. This was changed by a discovery made by Boris Belousov, a

Soviet The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...

scientist, in the 1950s. He created a

between different salts and acids that swing back and forth between being yellow and clear because the concentration of the different components changes up and down in a cyclic way. At the time this was considered impossible because it seemed to go against the

second law of thermodynamics The second law of thermodynamics is a physical law based on universal experience concerning heat and energy interconversions. One simple statement of the law is that heat always moves from hotter objects to colder objects (or "downhill"), unle ...

, which says that in a closed system the

entropy Entropy is a scientific concept, as well as a measurable physical property, that is most commonly associated with a state of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodyna ...

will only increase over time, causing the components in the mixture to distribute themselves until equilibrium is gained and making any changes in the concentration impossible. But modern theoretical analyses shows sufficiently complicated reactions can indeed comprise wave phenomena without breaking the laws of nature. (A convincing directly visible demonstration was achieved by

Anatol Zhabotinsky Anatol Markovich Zhabotinsky (Анато́лий Ма́ркович Жаботи́нский) (January 17, 1938 – September 16, 2008) was a Soviet biophysicist who created a theory of the chemical clock known as Belousov–Zhabotinsky reacti ...

with the Belousov–Zhabotinsky reaction showing spiraling colored waves.) The wave properties of the BZ reaction means it can move information in the same way as all other waves. This still leaves the need for computation, performed by conventional microchips using the

binary code A binary code represents text, computer processor instructions, or any other data using a two-symbol system. The two-symbol system used is often "0" and "1" from the binary number system. The binary code assigns a pattern of binary digits, als ...

transmitting and changing ones and zeros through a complicated system of

logic gate A logic gate is an idealized or physical device implementing a Boolean function, a logical operation performed on one or more binary inputs that produces a single binary output. Depending on the context, the term may refer to an ideal logic ga ...

s. To perform any conceivable computation it is sufficient to have

NAND gates In digital electronics, a NAND gate (NOT-AND) is a logic gate which produces an output which is false only if all its inputs are true; thus its output is complement to that of an AND gate. A LOW (0) output results only if all the inputs to the ...

. (A NAND gate has two bits input. Its output is 0 if both bits are 1, otherwise it's 1). In the chemical computer version logic gates are implemented by concentration waves blocking or amplifying each other in different ways.

Current research

In 1989 it was demonstrated how light-sensitive chemical reactions could perform

image processing An image is a visual representation of something. It can be two-dimensional, three-dimensional, or somehow otherwise feed into the visual system to convey information. An image can be an artifact, such as a photograph or other two-dimensio ...

. This led to an upsurge in the field of chemical computing. Andrew Adamatzky at the

University of the West of England The University of the West of England (also known as UWE Bristol) is a public research university, located in and around Bristol, England. The institution was know as the Bristol Polytechnic in 1970; it received university status in 1992 and ...

has demonstrated simple logic gates using reaction–diffusion processes. Furthermore, he has theoretically shown how a hypothetical "2⁺ medium" modelled as a cellular automaton can perform computation. Adamatzky was inspired by a theoretical article on computation by using balls on a billiard table to transfer this principle to the BZ-chemicals and replace the billiard balls with waves: if two waves meet in the solution, they create a third wave which is registered as a 1. He has tested the theory in practice and is working to produce some thousand chemical versions of logic gates to create a chemical pocket calculator. One of the problems with the present version of this technology is the speed of the waves; they only spread at a rate of a few millimeters per minute. According to Adamatzky, this problem can be eliminated by placing the gates very close to each other, to make sure the signals are transferred quickly. Another possibility could be new chemical reactions where waves propagate much faster. In 2014, a chemical computing system was developed by an international team headed by the Swiss Federal Laboratories for Materials Science and Technology (Empa). The chemical computer used surface tension calculations derived from the Marangoni effect using an acidic gel to find the most efficient route between points A and B, outpacing a conventional

satellite navigation A satellite navigation or satnav system is a system that uses satellites to provide autonomous geo-spatial positioning. It allows satellite navigation devices to determine their location ( longitude, latitude, and altitude/ elevation) to hig ...

system attempting to calculate the same route. In 2015,

Stanford University Stanford University, officially Leland Stanford Junior University, is a private research university in Stanford, California. The campus occupies , among the largest in the United States, and enrolls over 17,000 students. Stanford is conside ...

graduate students created a computer using magnetic fields and water droplets infused with magnetic

nanoparticles A nanoparticle or ultrafine particle is usually defined as a particle of matter that is between 1 and 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 10 ...

, illustrating some of the basic principles behind a chemical computer. In 2015,

University of Washington The University of Washington (UW, simply Washington, or informally U-Dub) is a public research university in Seattle, Washington. Founded in 1861, Washington is one of the oldest universities on the West Coast; it was established in Seatt ...

students created a programming language for chemical reactions (originally developed for DNA analysis). In 2017, researchers at

Harvard University Harvard University is a private Ivy League research university in Cambridge, Massachusetts. Founded in 1636 as Harvard College and named for its first benefactor, the Puritan clergyman John Harvard, it is the oldest institution of highe ...

patented a chemical Turing machine that operated using the non-linear dynamics of the Belousov–Zhabotinsky reaction. The system that they developed is capable of recognizing a Chomsky type-1 language using

Gibbs free energy In thermodynamics, the Gibbs free energy (or Gibbs energy; symbol G) is a thermodynamic potential that can be used to calculate the maximum amount of work that may be performed by a thermodynamically closed system at constant temperature an ...

considerations. This work was subsequently published in 2019, including systems for Chomsky type-2 and type-3 languages. In 2020,

University of Glasgow , image = UofG Coat of Arms.png , image_size = 150px , caption = Coat of arms Flag , latin_name = Universitas Glasguensis , motto = la, Via, Veritas, Vita , ...

researchers created a chemical computer using 3D-printed parts and magnetic stirrers in order to control the oscillations of BZ medium. In doing so, they were able to compute binary logic gates, and perform pattern recognition.

References

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"Introducing the glooper computer" - New Scientist article by Duncan Graham-Rowe
(Restricted access)

Theoretical computer science Quantum computing Theoretical chemistry Classes of computers Emerging technologies

Background

Current research

See also

References