As additive manufacturing industry analysts, we strive to predict evolving trends in 3D printing technologies over a five to ten year time frame. As journalists, we sometimes venture further into the future, trying to imagine what will happen fifty or a hundred years from now. What if we looked beyond, without a predefined time limit? Then we would need to speak with a scientist to understand what can and cannot happen in the end. And that’s what we did when we had the unique opportunity to interview Chiara MarlettoResearcher in the Department of Physics at the University of Oxford.
Professor Marletto is a theoretical physicist and her studies focus on quantum theory of computation, information theory, thermodynamics, condensed matter physics and quantum biology. She just published a book called The science of can and can’twhich is based on his recent research exploiting a recently proposed generalization of quantum information theory – constructor theory – to solve the problems underlying control and causality theory in physics.
In the book, she also explores the concept of the universal constructor, which could represent the ultimate evolution of today’s 3D printers. “It is not the main part of the book – says Professor Marletto – but it is the inspiring principle of the science of counterfactuals – the science of can and can’t – which is commonly called”Constructor theory‘ is the universal constructor theory.
But what exactly is a Universal Constructor? And what does this have to do with today’s 3D printers? One possibility that comes to mind is something like the “replicator” depicted in the fictional Star Trek series, which is a machine that assembles objects on an atomic level. In a way, it is. The universal constructor was proposed as a theoretical model by physicist and mathematician John von Neumann in the 1950s to generalize the idea of the universal Turing machine, i.e. the universal computer. “A universal computer is a machine that can be programmed to perform any physically possible calculation – explains Marletto – the universal constructor, on the other hand, is a machine that can perform any transformation – not just calculations – which is physically allowed. In particular, von Neumann designed it to mimic the behavior of cells, which can self-reproduce.
One element that the Universal Builder shares with 3D printers – which is also one of the defining characteristics of the Universal Builder – is that it could make a replica of itself, which inspired the first RepRap 3D printing movement. and continues to define 3D printers even at the highest industrial level: the ability to manufacture parts for new printers.
Another key concept is that the Universal Constructor requires not only energy and/or raw materials, but also knowledge, which, Professor Marletto explained, is a particular type of information contained in a software program, which must be provided as input to the universal computing machine. and also to the universal constructor so that they can perform the desired calculation. The next question is: if we had enough of all these elements (energy/materials and knowledge), could we make a 3D printer capable of making everything?
“We don’t currently have a complete theory of the Universal Constructor,” says Professor Marletto, “so your question doesn’t have a definite answer. It depends a lot on the resources available in the universe and other aspects of our physical laws. However, we can say that there is no physical law that prevents creation in a Universal Construct. In other words, the laws of physics as we understand them today allow creation of a machine capable of producing anything: the fact that this is incredibly complex with our current technological capacities does not mean that it is impossible as it would be, because for example, to create perpetual motion machines, which are prevented by the principle of conservation of energy.
“For example, adds Professor Marletto, the theory of thermodynamics tells us that there is no limit to the construction of arbitrarily precise heat engines, and we would also like to generate such a prediction for the universal constructor. We would like really to have, when the theory of the Constructor is finished, a series of physical principles which indicate if it is possible to have a Universal Constructor, and also which are the transformations which are in its repertoire.
While we don’t know if 3D printers can eventually evolve into universal builders, there’s nothing in physics that says they can’t. Either way, it may be possible to imagine an evolutionary process that takes us from today’s first 3D printers to a machine that can build anything. Professor Marletto agrees: “The eventual realization of a universal constructor will require the creation of imperfect constructors, which are not universal but have the ability to construct approximate constructors that perform slightly better than the previous generation. This mechanism – of how imperfectly reproducing organisms can create a better version from time to time, which then takes over – is already described in Charles Darwin’s theory of natural selection. A similar mechanism occurs within the framework of the technological evolution within our civilization, which proceeds gradually. Think of the evolution of computer machines, starting from the theoretical proposition of Turing.
The fact that the most optimized shapes produced by 3D printers often reproduce “natural shapes” such as lattices and fractals may be another key element that indicates that they will evolve: not only do they reproduce natural shapes, but they may also possibly reproduce natural processes such as self-reproduction and natural selection. Today’s 3D printers are evolving in terms of size and speed but also in terms of precision. As resolutions become more and more precise, the assembly of matter on the most elementary scale cannot escape the complexities of quantum mechanics. While most 3D printers today work with 10-100 micron voxels, some can already go down to the nanometer scale. And quantum effects can already come into play.
“Spontaneous quantum effects are usually confined to the atomic or subatomic scale,” Professor Marletto points out. “However, there are technologies that can induce quantum effects at mesoscopic scales. Consider, for example, interferometry expressions for complex molecules such as fullerenes. There are no limits set by quantum theory regarding the scale at which quantum effects can be used to improve the efficiency of a classical physical process. Think for example of the case of quantum biology – where the possibility is studied that living beings use quantum effects to function more efficiently. It is certainly possible to imagine ways to use quantum effects also in the Universal Constructor.
Before even getting into quantum effects, 3D printers must constantly come to terms with macro-scale physics and its limitations. For example, in terms of heat management, mechanical movements, in the physics of powders and liquids or in the physics of energy sources such as lasers and infrared radiation. Can builder theory and the science of Can and Can’t also provide a practical framework for addressing some of these challenges?
Professor Marletto thinks so. “The laws of constructor theory are, like all the laws of fundamental physics, universal,” she confirms. “They therefore apply to elementary systems such as particles, but also to aggregates of elementary particles which become more and more complex – therefore also to objects such as computers or living organisms.” Reading the professor’s book, one gets the impression that constructor theory could help broaden the horizons of creativity and innovation, especially in an innovation-rich and rapidly changing industry segment such as additive manufacturing, that continues to cross borders.
Another practical aspect to consider as 3D printing continues to advance is process simulation (and monitoring). Industrial 3D printers produce huge amounts of digital data that must be processed by increasingly powerful computers. Professor Marletto agrees this could be an ideal task for tomorrow’s universal quantum computers. “The Universal Constructor technology – when implemented – will use a quantum universal computer to manage the data and perform the calculations needed to operate the constructor,” she explains.
Having the opportunity to discuss the evolution of 3D printing technology in terms of theoretical physics was truly inspiring. While we are certainly still at the very beginning of the evolution of 3D printing, and still far from a full understanding of builder theory, it is clear that there are many common elements to explore. While 3dpbm is actively working with Sarah Goerke at Women in 3D Printing to drive inclusion and gender equality in the AM industry, I have to say it was also refreshing to talk about these topics with a brilliant woman scientist, in a world of theoretical physics that is also generally dominated by men.
“I think it’s about the changing times,” Professor Marletto concludes. “In my opinion, work and study choices (for both men and women) are largely determined by the culture and society in which we live. I expect that with the evolution (hopefully for the better) of our costumes there will be an evolution of the choices that will go hand in hand. We will see what this will lead to. I’m confident.”