The most active area of development in molecular assembly nanotechnology for the next few decades at least will be chemical reaction pathway discovery. It’s all well and good to imagine Drexlerian assembly lines of molecules using digital error correction to compensate for optical, phononic, thermal and acoustic noise. But there’s a reason life on Earth favored molecules that naturally want to get together like little complementary magnets. Presumably it should be possible to develop useful pathways that include inorganic and organometallic molecular compounds. But they need to be discovered. In this I find the Lego analogy slightly misleading. It’s more like a hilly maze that changes it’s layout as you run through it. Legos go together and come apart more or less with the same energy, whereas atoms in molecules run down the hill of entropy. Life harnesses these exothermic reactions to power its chemistry. This is what we must do as well.
One excellent use of Shannon’s understanding of digital noise, however, may be that we can use it to get these reactions to operate at higher temperatures and therefore faster rates. When you machine something out of a blocks of metal and assemble the parts, most of the metal stays locked in it’s crystals. When chemical changes are rapidly induced through the metal (tempering a blade for instance), it takes a lot of thermal energy. Even the polymers in 3D printers are still bulk materials (albeit using additive instead of subtractive manufacuring). Achieving a fine detailed molecular structure at a similar pace is perhaps the least trivial hurdle facing nanoassembly. There are good thermodynamic reasons that biological tissue takes so long to build up a big complex organism. When an organism does need to deploy mass chemical change rapidly to fight off an infection, the real danger is often the fever that can damage delicate tissue.
TL;DR - Only if we can learn to transfer heat out of a molecular assembly process will we be able to assemble large molecularly precise products on timescales comparable to 3D printing. This is indeed a problem of information theory. The polymers in 3D resins are simple patterns the molecules naturally want to make as they cool down. Molecular machinery where complexity is as detailed as a Lego design of atoms will require far more precision, of which heat is the enemy.
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