Nanotechnologies: current problems and general limitations I have some questions about Nanotechnologies. I'm not physicist and my knowledges about the topic are limited by the "Engines of Creation" book by Eric Drexler. So I think that my questions are related mostely to popular science.


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*As far as I know the molecular mechanisms like nanoassemblers and nanofactories exist in nature(I mean alive cells). Why have they not been created artificially by now?

*In case that they have been artificially created yet, do they have any limitations in developing of macro objects?
For instance, macromechanisms which exist in nature like animals are grow very slowly(months and years) and the initial program(i.e. DNA encryption) doesn't allow to make accurate copies. I mean that the twins who are growing from the same genetic material have a significant difference in adulthood(i.e. different phenotypes). Is this phenomena the result of some fundamental low of nature like Heisenberg uncertainty principle or any other that can't be resolved by modern technological methods?

*What are the top well known laboratories and organisations in the world which are engaged to resolve such kind of problems?
Thanks in advance.
 A: *

*Laws of classical mechanics cannot just be scaled down to the nano-regime, as alot of additional forces come up (chemical interaction, friction must be inspected newly, cannot be described by rough material parameters as in classical mechanics). Also microfabrication is a highly tricky process, especially if u want to do it in a parallel style fabrication process (e.g. integrated circuits only with limited resolution possible currently) or serial process (e.g. e-beam lithography). Industrial mass production for nano-machines is still a major problem to be solved. 

*Evolution is a process of trial & error under external circumstances on a carbon basis. Synthetic biology already is able to synthesize distinct molecule chains. Generally, "Self organisation" is a major topic in physics, but mostly ruled by non-linear processes which will lead to chaotic results often without heavy controlling and deeply understanding the distinct system. So engineering complex machines build from the nano bottom up and not top down is highly tricky thing. Be patient and give us more time plz ;) Having nano-machines that reproduce and organize themselves out of a few with some raw material is still a bit science fiction

*We have the the century of NANOPHYSICS. Every major physics department will do research in it. Depending what science field you prefer, from spintronics - photonics, NEMS, microfabrication methods, material research. Most department do specialize on specific topics, as laboratory hardware is pretty expensive. 

A: Your questions may be confusing your enquiry by too closely comparing DNA-based life and nanotech. Although they both operate at a nanoscale to create much larger objects they are very different in approach.
DNA is the end result of many trillions of random events. Various simple molecules that tended to create more of themselves eventually resulted in more complex chemical mixtures that eventually resulted in the first very very basic cells and the resulting explosion of activity we call "life".
In the same way that you would not call a tree blown down across a stream a "designed, engineered and constructed" bridge you cannot compare DNA with mature nanotech.
Even basic nanoassembler doesn't exist yet because the engineering techniques have not progressed that far.
There will be limitations on what can be created but they are not in the direction you are wondering about.
Mostly they will be related to the physical limitations of molecules. They can only withstand so much force/heat etc before changing their structure. Heisenberg's uncertainty, like all physical laws, will of course apply but that law doesn't cover large scale uncertainty such as the twins. It effectively covers utterly tiny quantum events (well below the nano scale but still possible effecting engineering of it.)
The limitation I believe you are interested in is the complexity of the object created.
A life form is highly complex (once built) because of the vast chaotic detail within it.
This complexity would require vast computational resources to analyse and reconstruct.
Compare that to using nanotech to build a kilometer cube of diamond. The instructions for that would be simple enough for a child to memorise.
Note that the DNA molecules themselves are relatively simple compared to the entire adult organisim.
Note that the vast computational resources required to handle the design of lifeforms (particularly their brains) may be available if nanotech is used to build extremely powerful computers.
Practically every large science research group is involved in nanotech.
Current research has a long way to go to get to the stage of Drexler style mature nanotech. Most research these days is around using techniques such as molecular chemistry and integrated circuit technology to create very large volumes of material which has nanoscale features. Microelectromechanical systems (MEMS) is also a promising area.
