What is the difference between 3 D printing at nanoscale resolution and molecular manufacturing?
3D printing can include that, but it’s not commercially available in a machine yet. It’s all additive manufacturing.
Great answer thanks @Chris_Thompson1
3d printing generally involves either additive or subtractive modeling of something out of a few distinct substances - at the nano scale, this is done with two lasers and involves a single substance.
Molecular manufacturing is a conceptual (at the moment) field that would involve atomic level precision control over multiple types of atoms, resulting in the construction of new and unique molecules, and nanoscale or larger structures that are precise at an atomic level.
You would not be far off to envision molecular manufacturing as the end-game of 3d printing, at a point where you can change the atom being placed at every step - but this is not likely to be the actual mechanism, in the end.
Rather, it is more probable that chemical and physical reactions at that scale will be used in concert with precise placement of atoms and/or molecules - so for example, a framework might be constructed, 3d printing style, then suffused with a type of molecule that adheres to certain patterns on the surface, then treated with ultraviolet, etc, in a multiple step, multiple operation process similar to current semi-conductor manufacturing.
In the longest time scales, molecular manufacturing might be accomplished by nano-scale machines - nanorobots, or nanobots - under the guiding direction of a computer combined with simple rule systems reacting to chemical gradients, in an artificial process not terribly dissimilar to that of multi-cellular growth and development.
There is a slightly higher level form of potential manufacturing sometimes referred to as smart sand, which would be small nano-scale robots that simply grasp each other in a desired pattern to form an object - you can imagine a box of LEGO or similar plugging bricks, where instead of carefully placing them, they would adhere to each other only if their position matched a desired pattern. This would be nanoscale manufacturing that would not be 3d printing, but neither would it really qualify as molecular manufacturing, as no novel molecules would be formed in the process, nor would anything be placed on quite that level of precision.