John Gauch, professor of computer science and computer engineering, was happy to answer:
In order to replicate objects, we must first be able to make extremely accurate 3D models of the objects we want to make. Our current MRI and CT scanners let us create images with resolutions of thousands of dots per inch. But in order to create the quality of objects they can make on Star Trek, we will need scanners with billions of dots per inch. Furthermore, we will need to know the chemical/molecular composition of each of these dots. The current generation of MRI and CT scanners only give us size/density information.
Secondly, we will need 3D printers that can output a huge range of materials – metal, plastic, paper, wood, cloth – in order to replicate most real-world objects. The current idea of squirting out liquids will work for some things, but not for others that cannot be melted and reformed easily. I think this will actually be a harder problem to solve than the modeling problem above.
And finally, creating objects that are alive would be the “final frontier.” I can see us creating something simple like an algae in the near future, but replicating more complex plants, insects, or animals would be a huge technical and ethical challenge. I can imagine some science fiction worst-case scenarios where we create something – like a tribble – that escapes the lab and takes over the earth!