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Swarms of Microrobots Over Europe?
Roland Piquepaille writes "In 'Mini robots to undertake major tasks?,' IST Results describes a EU-funded project which allowed to build several kinds of microrobots in the last three years. These robots are very small (about 1.5 cm by 3 cm), have limited on-board intelligence and are wirelessly controlled by a central robot control system. A follow-on project has already started, with an even more ambitious goal: deploy 'real' swarms of up to 1,000 robot clients. Such robot swarms are expected to perform 'a variety of applications, including micro assembly, biological, medical or cleaning tasks.' Read more for additional details, pictures and references about this follow-on project not described by the article mentioned above."
Well such an idea sounds reasonable enough. In fact in Richard Feynman's "plenty of room at the bottom" famous speech, he describes something similar: building small machines that are then used to build even smaller machines, until finally you have atomic-scale machines. This speech is considered by many to be the "original idea" for nanotechnology.
So why don't we have nanobots yet? Well it turns out its a little more complicated than that. The basic problem is that designs for large-scale robots do not work at smaller scales. You can take macroscopic engineering principles and scale them up or down to a point, but eventually they break down. The design of a 200ft long bridge is not just a 4X scale version of a 50ft bridge, after all.
If you read Drexler's technical book on the subject (Nanosystems) he goes into detail on how various properties (strength, elasticity, conductivity) scale down to the nano realm. Some of them scale favorably, whereas others do not. Thus nano-scale robots will not merely be "small versions" of macro robots. For instance the viscosity of a liquid becomes much more important than gravity, at small scales (whereas at large scales dealing with inertia and gravity are important).
My point is that robots cannot simply build exact (but smaller) copies of themselves. The half-sized robots will be useless within a generation or two, and will require new designs, optimized for that size. (Added to that, robot designs that are self-replicating are not trivial to begin with, at any size-scale!)
A lot of things don't scale well. For example, if you have a bearing wtih a very small tolerance to roll around in, if you shrink the entire thing down to say, 50% its size, the bearing will sieze because the gap is not large enough to allow the grease molicules to move around anymore. You can't shrink the grease molicules so they don't fit right anymore.
Electrical insulators are a certain thickness to protect against arcing of a certain voltage. If you cut the thickness of an insulator in half and don't cut the voltage in half, the insulator will likely be compromised by the voltage and you'll get a short or an arc.
Certain effects, such as viscosity and magnetism, don't change linearly with change in distance. When two magnets get twice as close as they used to be, the attractive/repulsive forces are now four times as great. Since you've probably also just cut your structure thicknesses in half, they are now much weaker, and the magnets being stronger produces an exponentally rising imbalance. In the end the magnets will deform your construction.
When mechanical devices get very small, they also encounter new hazards you take for granted. A grain of sand in a gas tank isn't a big deal, until the gas tank has shrunk to 1cc. Minor vibration or mechanical shock becomes more dangerous in some respects, and becomes nonexistent in others. Parts that are designed to float with eachother will stick since they are not receiving the benefitial effects of vibrations normally present.
Combustion and other important chemical and physical reactions work very differently at larger and smaller scales.
Other factors also cause problems at small scales. Capilary effect, static attraction, surface tension, it's a whole new world when you get really small, especially when any liquids are involved. I think that's why we have physics, astrophysics, and quantum physics... the rules change when you radically alter size.
So there are actually a lot of things to consider when trying to shrink something. It's not just a matter of making all the parts smaller.
I work for the Department of Redundancy Department.
Has anyone even made a robot that can build a replica of itself, by itself?
For every expert, there is an equal and opposite expert. - Arthur C. Clarke