1) Is there anything nanotechnology can't do? What are its limits?
It must work within the limits of physical laws. Available matter, available energy, heat generation, relativity, and quantum mechanical uncertainty all set limits on what can be done.
2) Is nanotechnology the last technology?
The subtitle to K. Eric Drexler's book
Engines of CreationisChallenges and Choices of the Last Technological Revolution. The implicit assumption being no other technologies will follow with equivalent impact. Is that a reasonable assumption? Perhaps, perhaps not. At a smaller scale and larger energy range are nuclear technologies. Or additional dimensions. The exact physical laws for this scale have yet to be worked out in full detail. At very large scales (planetary and solar system size and up) there has only been speculation on possible technologies. The same is true for attainment of high relativistic speeds. Breakthroughs in these realms might lead to technologies as revolutionary as nanotechnology.
3) Doesn't Heisenberg's Uncertainty Principle forbid the possibility of nanotechnology?
Technical:
Assume that we want to place a carbon atom on a specific previously-positioned atom. We need to position it to within roughly a bond length in order to have it bond to the right atom. A typical bond length is around an Angstrom, 0.1 nm or 10^-10 meters.
Heisenberg's uncertainty principle says:
sigmaX * sigmaP >~ hbar/2 (eq. 4.12, Nanosystems)
Here, sigmaX = 10-10 meters, hbar/2 = 5.3 * 10-35 Joule*seconds (or kg*m2/s) so deltaP >~ 5.3 * 10-25 kg*m/s.
Our carbon (12) atom has a mass of 2 * 10-26 kilograms, so the uncertainty in its velocity is 5.3 * 10-25 / 2 * 10-26 = 26.5 m/s.
To put it another way, the zero-point energy it must have in order to be confined in this space is roughly sigmaE = ½*m*v2 = ½*2*10-26 kg * (26.5 m/s)2 = 7 * 10-24 J, which is 500 times less than thermal energy, 4 * 10-21 J, at room temperature. So thermal oscillations generate a greater positional uncertainty than quantum uncertainty does. {JS}
Less Technical:
The uncertainty principle states that particles can't be pinned down to an exact location for any length of time. It limits what molecular machines can do, just as it limits what anything else can do. Nonetheless, calculations show that the uncertainty principle places few important limits on how well atoms can be held in place, at least for the purposes of nanotechnology. The uncertainty principle makes electron positions quite fuzzy, and in fact this fuzziness determines the very size and structure of atoms. An atom as a whole, however, has a comparatively definite position set by its comparatively massive nucleus. If atoms didn't stay put fairly well, molecules would not exist. One needn't study quantum mechanics to trust these conclusions, because molecular machines in the cell demonstrate that molecular machines work well. {KED}
4) Won't thermal fluctuations damage nanomachines?
As mentioned in the answer above, room temperature thermal energy will jiggle atoms around on average by about 4 * 10-21 Joules. But atomic bond energies are on the order of 1 electron volt (eV). If we translate all the mentioned energy units to electron volts, so smaller exponents come into play, we get this set of energy ranges: * ~ 0.00004 eV QM sigmaE for carbon confined to 1 Angstrom. * ~ 0.025 eV average thermal energy at room temperature (~293 K). * ~ 1 eV order of magnitude for typical molecular bond strengths. So the average fluctuations would not break a typical molecular bond. However, because some fluctuations are well above the average, some damage will occur. Further details on the rate at which this damage occurs may be found in K. Eric Drexler's text "Nanosystems". Generally the rate would be low enough to be tolerable for many systems and self-repair mechanisms would be needed for systems where damage is less tolerable.
5) Can nanotechnology be used to do nuclear transmutation?
Not directly. Chemical reactions are on the order of a few electron volts. Nuclear reactions are on the order of a few hundred thousand to millions of electron volts.
6) What alternatives are there to carbon or diamonoid materials?
Silicon oxides have been proposed. They have the advantage that the Earth and its moon contain large quantities of silicon. See http://www.foresight.org/Conferences/MNT05/Papers/Gillett1/.
7) How fast would a carbon nanotube computer be?
At present no analysis for nanotube based optoelectronic, moltronic, spintronic or molecular quantum computers has been brought to our attention.
Drexler's original work did cover rod-logic computing systems in his book Nanosystems. Chapter 12 covers the technical aspects of such devices and comes to the conclusion;
Nanomechanical computing systems can be implemented using logic systems based on sliding rods having switching times of ~0.1ns, with energy dissipation R kT300 per gate. Register cells can be constructed that approach the theoretical minimum energy dissipation of ln(2)kT. Logic rods and registers can be joined to build register-to-register combinatorial logic systems that achieve four register-to-register transfers in ~1.2ns; this performance suggests that nanomechanical RISC machines can achieve clock speeds of ~1GHz, executing instructions at ~1000 MIPS [in bus speed to compare with an Intel Pentium this would be a ~4GHz CPU]. Fast carry chains, RAM, Tapes and I/O systems all appear feasible.
A CPU-scale system containing 10e6 transistor-like interlocks can fit within a 400nm cube. Compatible systems for clocking, power supply, and cooling have been described and analysed. The power consumption for a 1GHz, CPU-scale system is estimated to be ~60 nW, performing >10e16 instructions per second per watt.
8) Can nanotechnology be used to recycle trash and landfills? And if it can, how will it?
There has been some discussion on the possibility. Early conclusions were that it would be economically infeasible to simply speed up the biodegrading process. Recycled into useful resources as a byproduct was a better solution, but the wide range of chemicals in a landfill proved to be a problem.
Recently Dr Wiwat Tantapanichkul, a nanotechnology expert from Chulalongkorn University's Faculty of Engineering has proposed the use of nanotechnology to turn garbage into chemicals for wastewater treatment.
The idea is to use solid wastes like used tyres, charcoal dust and coffee waste to produce activated carbon, which then could be used in wastewater treatment plants.
So far the published plans do not explain whether the recycling is to be done in-situ or materials excavated then treated.
9) How can MNT manufacture food? Will it taste good? Will it be good for you?
Although not strictly MNT, one of our members has proposed a workable nanotech based food synthesizer. Details on its workings, and the quality of its output are available.
10) How fast can nanites construct a house? Car? Steak dinner? Island?
There is no answer to this question at the current time. It depends very much on the design for man-made objects. Food is covered in Q9
11) Can nanotechnology be used to extract gold from sea water?
There are about 10 micrograms of gold per ton of sea water. At current prices (rough estimate) 10,000 tons of water contains a dollar's worth of gold. At the prices I pay, a dollar's worth of electricity is not enough to pump that much water more than a couple of inches (with pumps a lot more efficient than the one I've got now). The magnesium in a given volume of sea water is worth a lot more than the gold in the same volume. So is the salt. In the future, it may also become worthwhile to recover the deuterium. {Posted by JoSH in November of 1992}
12) What can a nanotech-enhanced human body do? What can't it do?
Answers to this depend on the degree of alteration. With little alteration it is possible to 'update' anybody to have the fitness, strength and general health of a trained athlete. These changes are already attainable by anyone with enough willpower to do the work, nanotech will simply speed the process and make it easier.
Once you remove the 'human' limit there are a large number of alterations ranging from simple bone and muscle replacement to complete body surgery changing shape and form entirely. Some of these are already possible with current (drastic) plastic surgery but new nanotech materials and processes will make these safer, cleaner and increase the range of possibilities.
Robert A. Freitas Jr. has done a lot of work in the ongoing Nanomedicine Project, which covers technical specifications and limits for human biological improvements in greater detail than is possible here. (also see Q13 below) {AJ}
13) How invincible is a nanotech-enhanced human body?
This is highly dependent upon the nature of the enhancements. Unsubstantiated conjectures come and go with some frequency on the sci.nanotech newsgroup. Some more thoroughly researched proposals have been put forth by Robert Freitas, author of "Nanomedicine".
- Respirocytes
The artificial red blood cell or "respirocyte" is a blood borne spherical 1-micron diamonoid 1000-atm pressure vessel with active pumping powered by endogenous serum glucose, able to deliver 236 times more oxygen to the tissues per unit volume than natural red cells and to manage carbonic acidity. An onboard nanocomputer and numerous chemical and pressure sensors enable complex device behaviours remotely reprogrammable by the physician via externally applied acoustic signals. Primary applications will include transfusable blood substitution; partial treatment for anaemia, perinatal/neonatal and lung disorders; enhancement of cardiovascular/neurovascular procedures, tumour therapies and diagnostics; prevention of asphyxia; artificial breathing; and a variety of sports, veterinary, battlefield and other uses.
- Clottocytes
Platelets gather at a site of bleeding. There they are activated, becoming sticky and clumping together to form a plug that helps seal the blood vessel and stop the bleeding. At the same time, they release substances that help promote clotting. Natural blood coagulation is a complex process involving platelets, red and white cells, endothelial cells, an array of coagulation factors, fibrinolytic proteins and protease inhibitors whose contributions wax and wane over time.
An artificial mechanical platelet or clottocyte may allow complete hemostasis in as little as ~1 second, even in moderately large wounds. This response time is on the order of 100-1000 times faster than the natural system. Our baseline clottocyte is conceived as a serum oxyglucose-powered spherical nanorobot ~2 microns in diameter (~4 micron3 volume) containing a fiber mesh that is compactly folded onboard. Upon command from its control computer, the device promptly unfurls its mesh packet in the immediate vicinity of an injured blood vessel -- following, say, a cut through the skin. Soluble thin films coating certain parts of the mesh dissolve upon contact with plasma water, revealing sticky sections (e.g., complementary to blood group antigens unique to red cell surfaces) in desired patterns.
NOTE: There have been some objections to this design on grounds of mesh size and strength, put forward by Hal Finney (follow the sticky points in the article text for more details).
- Microbivores
The future nanorobotic equivalent of the third major class of natural blood cells - the white cells. Microbivores constitute a potentially large class of medical nanorobots intended to be deployed in human patients for a wide variety of antimicrobial therapeutic purposes, for example as a first-line response to septicaemia.
While macrophages can ingest up to ~25% of their volume per hour, microbivores can process ~2000% of their volume per hour... a given volume of microbivores can digest bacterial pathogens 80 times faster than an equal volume of white cells or macrophages could digest them.
Microbivores could also be useful for treating infections of the meninges or the cerebrospinal fluid (CSF) and respiratory diseases involving the presence of bacteria in the lungs or sputum, and could also digest bacterial biofilms. These handy nanorobots could quickly rid the blood of nonbacterial pathogens such as viruses (viremia), fungus cells (fungemia), or parasites (parasitemia). Outside the body, microbivore derivatives could help clean up biohazards, toxic biochemicals or other environmental organic materials spills, as in bio remediation.