Drexler believes that not only are stable gears possible, but that every component of a modern, macroscale assembly-line can be shrunk to the nanoscale. He believes this because his calculations, and some experiments show that this works.
He believes that ” Nanomachines made of stiff materials can be engineered to employ familiar kinds of moving parts, using bearings that slide, gears that mesh, and springs that stretch and compress (along with latching mechanisms, planetary gears, constant-speed couplings, four-bar linkages, chain drives, conveyor belts . . .).”
The power to do this comes from 2 sources. First of all, the “feedstock” to a nanoassembly factory always consists of the element in question bonded to other atoms, such that it’s an energetically favorable reaction to bond that element to something else. Specifically, if you were building up a part made of covalently bonded carbon (diamond), the atomic intermediate proposed by Drexler is carbon dimers ( C—C ). See http://e-drexler.com/d/05/00/DC10C-mechanosynthesis.pdf
Carbon dimers are unstable, and the carbon in question would rather bond to “graphene-, nanotube-, and diamond-like solids”
The paper I linked shows a proposed tool.
Second, electrostatic electric motors would be powered by plain old DC current. These would be the driving energy to turn all the mechanical components of an MNT assembly system. Here’s the first example of someone getting one to work I found by googling : http://www.nanowerk.com/spotlight/spotid=19251.php
The control circuitry and sensors for the equipment would be powered the same way.
An actual MNT factory would work like the following. A tool-tip like in the paper I linked would be part of just one machine inside this factory. The factory would have hundreds or thousands of separate “assembly lines” that would each pass molecules from station to station, and at each station a single step is perfomed on the molecule. One the molecules are “finished”, these assembly lines will converge onto assembly stations. These “assembly stations” are dealing with molecules that now have hundreds of atoms in them. Nanoscale robot arms (notice we’ve already gone up 100x in scale, the robot arms are therefore much bigger and thicker than the previous steps, and have are integrated systems that have guidance circuitry, sensors, and everything you see in large industrial robots today) grab parts from assembly lines and place them into larger assemblies. These larger assemblies move down bigger assembly lines, with parts from hundreds of smaller sub-lines being added to them.
There’s several more increases in scale, with the parts growing larger and larger. Some of these steps are programmable. The robots will follow a pattern that can be changed, so what they produce varies. However, the base assembly lines will not be programmable.
In principle, this kind of “assembly line” could produce entire sub-assemblies that are identical to the sub assemblies in this nanoscale factory. Microscale robot arms would grab these sub-assemblies and slot them into place to produce “expansion wings” of the same nanoscale factory, or produce a whole new one.
This is also how the technology would be able to produce things that it cannot already make. When the technology is mature, if someone loads a blueprint into a working MNT replication system, and that blueprint requires parts that the current system cannot manufacture, the system would be able to look up in a library the blueprints for the assembly line that does produce those parts, and automatically translate library instructions to instructions the robots in the factory will follow. Basically, before it could produce the product someone ordered, it would have to build another small factory that can produce the product. A mature, fully developed system is only a “universal replicator” because it can produce the machinery to produce the machinery to make anything.
Please note that this is many, many, many generations of technology away. I’m describing a factory the size and complexity of the biggest factories in the world today, and the “tool tip” that is described in the paper I linked is just one teensy part that might theoretically go onto the tip of one of the smallest and simplest machines in that factory.
Also note that this kind of factory must be in a perfect vacuum. The tiniest contaminant will gum it up and it will seize up.
Another constraint to note is this. In Nanosystems, Drexler computes that the speed of motion for a system that is 10 million times smaller is in fact 10 million times faster. There’s a bunch of math to justify this, but basically, scale matters, and for a mechanical system, the operating rate would scale accordingly. Biological enzymes are about this quick.
This means that an MNT factory, if it used convergent assembly, could produce large, macroscale products at 10 million times the rate that a current factory can produce them. Or it could, if every single bonding step that forms a stable bond from unstable intermediates didn’t release heat. That heat product is what Drexler thinks will act to “throttle” MNT factories, such that the rate you can get heat out will determine how fast the factory will run. Yes, water cooling was proposed :)
One final note : biological proteins are only being investigated as a boostrap. The eventual goal will use no biological components at all, and will not resemble biology in any way. You can mentally compare it to how silk and wood was used to make the first airplanes.
From reading Radical Abundance :
He believes that ” Nanomachines made of stiff materials can be engineered to employ familiar kinds of moving parts, using bearings that slide, gears that mesh, and springs that stretch and compress (along with latching mechanisms, planetary gears, constant-speed couplings, four-bar linkages, chain drives, conveyor belts . . .).”
The power to do this comes from 2 sources. First of all, the “feedstock” to a nanoassembly factory always consists of the element in question bonded to other atoms, such that it’s an energetically favorable reaction to bond that element to something else. Specifically, if you were building up a part made of covalently bonded carbon (diamond), the atomic intermediate proposed by Drexler is carbon dimers ( C—C ). See http://e-drexler.com/d/05/00/DC10C-mechanosynthesis.pdf
Carbon dimers are unstable, and the carbon in question would rather bond to “graphene-, nanotube-, and diamond-like solids”
The paper I linked shows a proposed tool.
Second, electrostatic electric motors would be powered by plain old DC current. These would be the driving energy to turn all the mechanical components of an MNT assembly system. Here’s the first example of someone getting one to work I found by googling : http://www.nanowerk.com/spotlight/spotid=19251.php
The control circuitry and sensors for the equipment would be powered the same way.
An actual MNT factory would work like the following. A tool-tip like in the paper I linked would be part of just one machine inside this factory. The factory would have hundreds or thousands of separate “assembly lines” that would each pass molecules from station to station, and at each station a single step is perfomed on the molecule. One the molecules are “finished”, these assembly lines will converge onto assembly stations. These “assembly stations” are dealing with molecules that now have hundreds of atoms in them. Nanoscale robot arms (notice we’ve already gone up 100x in scale, the robot arms are therefore much bigger and thicker than the previous steps, and have are integrated systems that have guidance circuitry, sensors, and everything you see in large industrial robots today) grab parts from assembly lines and place them into larger assemblies. These larger assemblies move down bigger assembly lines, with parts from hundreds of smaller sub-lines being added to them.
There’s several more increases in scale, with the parts growing larger and larger. Some of these steps are programmable. The robots will follow a pattern that can be changed, so what they produce varies. However, the base assembly lines will not be programmable.
In principle, this kind of “assembly line” could produce entire sub-assemblies that are identical to the sub assemblies in this nanoscale factory. Microscale robot arms would grab these sub-assemblies and slot them into place to produce “expansion wings” of the same nanoscale factory, or produce a whole new one.
This is also how the technology would be able to produce things that it cannot already make. When the technology is mature, if someone loads a blueprint into a working MNT replication system, and that blueprint requires parts that the current system cannot manufacture, the system would be able to look up in a library the blueprints for the assembly line that does produce those parts, and automatically translate library instructions to instructions the robots in the factory will follow. Basically, before it could produce the product someone ordered, it would have to build another small factory that can produce the product. A mature, fully developed system is only a “universal replicator” because it can produce the machinery to produce the machinery to make anything.
Please note that this is many, many, many generations of technology away. I’m describing a factory the size and complexity of the biggest factories in the world today, and the “tool tip” that is described in the paper I linked is just one teensy part that might theoretically go onto the tip of one of the smallest and simplest machines in that factory.
Also note that this kind of factory must be in a perfect vacuum. The tiniest contaminant will gum it up and it will seize up.
Another constraint to note is this. In Nanosystems, Drexler computes that the speed of motion for a system that is 10 million times smaller is in fact 10 million times faster. There’s a bunch of math to justify this, but basically, scale matters, and for a mechanical system, the operating rate would scale accordingly. Biological enzymes are about this quick.
This means that an MNT factory, if it used convergent assembly, could produce large, macroscale products at 10 million times the rate that a current factory can produce them. Or it could, if every single bonding step that forms a stable bond from unstable intermediates didn’t release heat. That heat product is what Drexler thinks will act to “throttle” MNT factories, such that the rate you can get heat out will determine how fast the factory will run. Yes, water cooling was proposed :)
One final note : biological proteins are only being investigated as a boostrap. The eventual goal will use no biological components at all, and will not resemble biology in any way. You can mentally compare it to how silk and wood was used to make the first airplanes.