Ultimately, rather than relying on a printer to place droplets of material, the logic for assembling an object will be built into the materials themselves. This is exactly how our bodies are made; a molecular machine called the ribosome translates instructions from genes into the series of steps required to assemble all of the proteins in our bodies out of the twenty amino acids. The discovery of building with logic is actually a few billion years old; it’s fundamental to the emergence of life. Current research is now seeking to do the same with functional materials, creating a fundamentally digital fabrication process based on programming the assembly of microscopic building blocks. This mechanism will be embodied in personal fabricators fed by such structured materials. Much as a machine today might need supplies of air, water, and electricity, a digital personal fabricator will use as raw feedstocks streams of conductors, semiconductors, and insulators.
Unlike machines of today, though, but just like a child’s building blocks, personal fabricators will also be able to disassemble something and sort its constituents, because the assembled objects are constructed from a fixed set of parts. The inverse of digital fabrication is digital recycling. An object built with digital materials can contain enough information to describe its construction, and hence its deconstruction, so that an assembler can run in reverse to take it apart and reuse its raw materials. We’re now on the threshold of a digital revolution in fabrication. The earlier revolutions in digitizing communications and computation allowed equipment made from unreliable components to reliably send messages and perform computations; the digitization of fabrication will allow perfect macroscopic objects to be made out of imperfect microscopic components, by correcting errors in the assembly of their constituents.
Return now to the mainframe analogy. The essential step between mainframes and PCs was minicomputers, and a similar sequence is happening along the way to personal fabrication. It’s possible to approximate the end point of that evolution today with a few thousand dollars of equipment on a desktop, because engineering in space and time has become cheap.