I'd started to write that I'm as fond of gadgets as the next man, but in truth I'm only as fond as the one after the one after him (which is still fairly fond). For example I get enormous pleasure from my recently-acquired Zoom G1on guitar effects pedal, frightening the neighbours with my PhaseFunk twangs. However I've resisted the hottest of today's gadgets, the 3D printer, with relative ease. Partly it's because I have no pressing need for one: being neither a vendor of cornflakes nor a devotee of fantasy games or toy soldiers I just don't need that many small plastic objects. I can see their utility for making spare parts for veteran mechanical devices, but I don't do that either. What deters me more though is the quasi-religious atmosphere that has enveloped 3D printing, as typified by those reverential terms "making" and "maker". People desperately want to bridge the gap between digital representation and real world, between CGI fantasy and life, and they've decided 3D printing is a step on the way, but if so it's a tiny step toward a very short bridge that ends in mid-air.
One problem is precisely that 3D printing tries to turn bits into atoms, but pictures don't contain the internal complexity of reality. Serious applications of 3D printing are, for example, the aerospace industry where components can be printed in sintered metal quicker, more cheaply and of greater geometric complexity than by traditional forging or casting techniques. Even so two things remain true: such parts are typically homogeneous (all the same metal) and made in relatively small quantities since 3D printing is slow - if you need 100,000 of something then 3D print one and make a mold from it for conventional casting. Printing things with internal structure of different materials is becoming possible, but remains topologically constrained to monolithic structures.
That's the second problem, that 3D printing encourages thinking about objects as monolithic rather than modular. Modularity is a profound property of the world, in which almost every real object is composed from smaller independent units. In my Penguin Dictionary of Computing I said: "modules must be independent so that they can be constructed separately, and more simply than the whole. For instance it is much easier to make a brick than a house, and many different kinds of house can be made from standard bricks, but this would cease to be true if the bricks depended upon one another like the pieces of a jigsaw puzzle." The basic module in 3D printing is a one-bit blob firmly attached to the growing object.
I recently watched a YouTube video about a project to 3D print mud houses for developing countries, and it was undeniably fascinating to watch the print head deposit mud (slowly) in complex curves like a wasp building its nest. But it struck me that, given the computing power attached to that printer, it would be faster to design a complex-curved brick mold, print some and then fill them with mud and assemble the houses manually.
The ultimate example of modularity, as I never tire of saying, is the living cell, which has a property that's completely missing from all man-made systems: every single cell contains not only blueprints and stored procedures for building the whole organism, but also the complete mechanism for reproducing itself. This mind-boggling degree of modularity is what permitted evolution to operate, by accidentally modifying the blueprints, and which has lead to the enormous diversity of living beings. No artificial "maker" system can possibly approach this status so long as fabrication remains homogeneous and monolithic, and once you do introduce heterogeneous materials and internal structure you'll start to confront insuperable bandwidth barriers as an exponentially-exploding amount of information must be introduced from outside the system rather than being stored locally. A machine that can make a copy of itself seems to really impress the maker community, but you just end up with a copy of that machine. A machine that copies itself, then makes either an aeroplane, or a bulldozer, or a coffee machine out of those copies is some way further down the road.
I was lead to these thoughts recently while watching Alex Garland's excellent movie Ex Machina. In its marvellous denouement the beautiful robot girl Ava kills her deeply unpleasant maker and escapes into the outside world to start a new, independent life, but first she has to replace her arm, damaged in the final struggle, with a spare one. Being self-repairing at that level of granularity is feeble by biological standards, and as she stood beaming at a busy city intersection it struck me that such spare parts would be in short supply at the local hospital...
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