What does the fictional replicator do?
First seen in 1987 on Star Trek: Next Generation, the replicator machine was used in many different ways, such as creating food and drink, building spare parts for the starship, and making clothes. Supposedly, it worked by rearranging subatomic particles, which are abundant everywhere in the universe, to form molecules and arrange those molecules to form any given object. For example, to create a pork chop, the replicator would first form atoms of carbon, hydrogen, nitrogen, etc… then arrange them into amino acids, proteins, and cells, and assemble the particles into the form of a pork chop. Replicators can also "recycle" by converting matter into energy. Following that principle, the device can dismantle any object into subatomic particles. The ensuing energy can then be stored for later use. At the time this idea was introduced, it was class I impossible, because although this concept didn't violate the know laws of physics, the technology just wasn't there.
What about in real life?
Today, we have what is known as 3D (three-dimensional) printing. Invented by Charles Hull, 3D printing was first called stereolithography – a technique for converting liquid into solid three-dimensional objects with lasers. It was created as a means of rapid prototyping for industrial design and patented in 1984 as "a system for generating three-dimensional objects by creating a cross-sectional pattern of the object to be formed at a selected surface of a fluid medium capable of altering its physical state in response to appropriate synergistic stimulation by impinging radiation, particle bombardment, or chemical reaction." Essentially, three-dimensional printers translate computer aided design (CAD) files into STL (stereolithography) files, cross-sectioning the image of whatever you want to make into layers of polygons the printer can replicate in a process called “additive manufacturing.”
Additive manufacturing is where layers of medium are added one on top of the other to create the final three-dimensional product, rather than “subtractive” manufacturing where items are cut out of material. Different mediums require different 3D printing processes: resins and metals are fused with lasers, while plastics are extruded drop by drop. The method of fusing resins and metals with lasers is closest to the original patent, and is used in industrial, engineering, and even electronic printing. In order to print three-dimensional objects out of resins and metals, the printer lays a layer of the liquid material while shining a UV laser onto it to harden it. The layer is thin, and the base material is an ultraviolet-curable photopolymer that allows the medium to dry quickly. After that layer is placed, the printer lays another one on top of it, and so on until the final 3D object is created. Of course, this is not exactly like the Star Trek replicator because a medium with which to print is still needed. Most of the similarities are in the uses.
So, what are the uses of 3D printing?
Just about any object can be 3D printed these days! Just a quick Google search will show you. Thanks to online design software and at-home printing machines, even regular people (with enough money for a machine) can 3D print. Some libraries are even installing printers for public use. Scientists have even been able to make human organs that are viable for transplant!
A little boat hat was 3D printed out of chocolate
Ok, but how does this have anything to do with physics?
Students may soon be able to reach out and touch some of the theoretical concepts they are taught in their physics classes, thanks to an idea devised by a group of researchers from Imperial College in London. In the study published on 9 December, 2013 in the journal EPL (Europhysics Letters), researchers have successfully demonstrated how complex theoretical physics can be transformed into a physical object using a 3D printer. In just eight hours and at the cost of around 15 euros ($15.82), they were able to use a commercially available 3D printer to create their own 8 cm3 object based on a mathematical model that described how forest fires can be started and how they eventually spread over time. The researchers have labelled the approach “Sculplexity”—standing for sculptures of complexity—and believe it could also be used to produce works of art based on science, or transform the way that ideas and concepts are presented and discussed within the scientific community. Co-author of the study, Dr. Tim Evans, a theoretical physicist at Imperial, said: “The work was inspired by a visit to the Victoria and Albert Museum in London where I came across the first ever 3D printed object the museum had acquired.“ The object was a table inspired by the tree-like structures found in nature, which is an example of a branching process that is commonly encountered in complex systems in theoretical physics. This led me to think, what other processes familiar to physics could be turned into a 3D printed object?"
Institute of Physics