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“”Drexler’s thesis is merely the source of the disease. What I’m really sick of are ding dongs trying to tell me toothpaste or golf balls is nanotech.
Nanotechnology (often referred to as "nanotech") is the art of working on materials at the nanometer (one billionth of a meter) scale, hence the name.
There is no single unified thing that can be called "nanotechnology." Rather, many different technologies and industries are reaching the point where nanoscale operations are of interest. In previous years, we might have called this "chemistry".
In practical terms (i.e., funding it), it's materials science — that is, chemistry — with "nano-" on the front because that gets funding from people who think they're paying for magical molecular robots. Emphasis on "magical." Nanotechnology advocates will regularly push a future of magical molecular robots, then point at chemistry as evidence for the magical molecular robots.
From the late 1980s on, it was popularised by K. Eric Drexler, in his 1986 book Engines of Creation: The Coming Era of Nanotechnology and the work of science fiction that Drexler used as a Ph.D. thesis. (Drexler's Ph.D. is much-touted as being from MIT, but was not awarded by an actual science or engineering department — he got it in the Media Arts and Sciences Section of the School of Architecture and Planning.)
Nanotechnology fanboys — as opposed to the people who actually work with the stuff — have a habit of downplaying Feynman's origination of the idea and playing up Drexler, possibly because the latter is far more indulgent of their fantasies.
Dr. Drexler, most upset that the National Nanotechnology Initiative insisted on only funding things that do not actually defy physics, has taken to using his new favored terms, "zettatechnology" or "atomic precision manufacture".
 In science woo
“”No, you don’t get it. You are still in a pretend world where atoms go where you want because your computer program directs them to go there.
|—Richard Smalley to Drexler|
The popular conception of nanotechnology is Eric Drexler's concept of nanobots, like industrial robots scaled down a billion times. This is entirely made of bollocks and would violate physics, chemistry, and thermodynamics. However, not many people realise why it's bollocks, as it isn't really due to us limiting what our technology might one day do, it's purely down to the physics of how the world works.
The rules of mechanics don't scale evenly with size — consider surface to volume ratios, which are why the energy consumed by small rodents per unit of mass is different from that for elephants, and why the aerodynamics of a Boeing 747 are different from a small 747-shaped toy. At the molecular level, the world is considerably different from macro scale. A solvent like water would feel more like treacle, and anything floating in it would be at the mercy of Brownian motion that would make even the strongest rip currents look quite weak.
Imagine what manufacturing would look like if your machines' gears rotated randomly, the size of the gears' teeth fluctuated randomly, everything (gears, grippers, working materials) was coated in glue and the whole factory burst into flames at the first hint of rust.
That Drexler has pushed an idea which is actually impossible has not deterred nanotech fans, who get as upset as they usually do when an expert in a field they're talking about points out they're simply wrong, apparently from an emotional sunk cost fallacy.
Transhumanists routinely casually throw biology out the window, but with nanobot advocacy they manage the same contempt for chemistry and physics. (Michael Anissimov, then of SIAI, advocated Digital Rights Management as the way to control dangerous science woo nanotechnology, thus also casually throwing mathematics out the window.) In cryonics, "but, nanobots!" is the standard answer to any objection. Some cryonics advocates are finally pointing out that this is not quite rational.
Advocates of nanotech woo often tag life "soft nanotech", as if that makes "hard nanotech" (woo) merely unrealised rather than impossible. This is in reference to the fact that such "hard" nano-tech seems to imply solid, robot-like structures (made of diamond, for example) while "soft" is closer to more malleable molecular structures. It's a bit like calling speech "soft telepathy" to imply that "hard telepathy" is a difference of degree, rather than kind.
 In fiction
Drexler's vision of nanobots is a standard science fiction trope for magic. Applications include superhuman healing and body repair, superhuman powers, shapeshifting machines, constructing large structures at a miraculous pace, self-repairing materials, instantly taking over and reprogramming any computer system or even a person. Alternatively, a swarm of nanomachines can be a weapon, eating anything in its path like locusts.
One common version is self-replicating nanomachines, which convert any available matter into more nanomachines to replenish and bolster their numbers. If left unchecked, these machines convert everything — the so called "grey goo" doomsday scenario. The idea of creating self-replicating machines, which was an early goal of nanotechnology, has given way to the safer and simpler approach of building larger (relatively speaking) factories that can mass-produce nanomachines, making this scenario less likely to occur in reality.
Writers like these little things because they don't have to show and explain how they work — all you see are the results.
A slightly more believable description of nanotechnology can be found in Neal Stephenson's book The Diamond Age].[wp] In this, not only is there a detailed description of how the machines would be built, there is even a discussion of associated problems, such as heat dissipation.
 In reality
Reality is rather duller than fiction — unless you like the actual science, of course.
Current nanotechnology focuses on creating much simpler structures, such as nanoparticles that can deliver drugs to specific cells, and materials with advantageous properties. Better understanding of materials at the nanoscale is explaining many apparently odd things. Nanoparticles (colloids) of gold are red, rather than yellow as the bulk metal is, and this effect is responsible for the colours of medieval stained glass. Some of the odd properties of soot are because it contains buckyballs (a.k.a., Buckminister Fullerene) and nanotubes. Scientists working on these nano-scaled advances tend to refer to it as either "chemistry" or "materials science", as "nanotechnology" is not a functioning research field in its own right and is just an umbrella term for a variety of research ventures that span multiple disciplines (and a handy buzzword to get funding from people who think they're buying magical robots).
Molecular recognition — the ability for catalysts to actively recognise and orientate their substrates — is an emerging area of research and could become the norm for chemical synthesis in a few decades. However, this still relies on normal chemical synthetic routes with one catalyst tuned to one reaction (or group of reactions).
Molecular nanotechnology, which aims to engineer mechanical systems at the molecular level, is barely in its infancy. The dream of assembling molecules "atom by atom" may not even be possible in the sense claimed by those writing about nanobots. So far, scientists are pretty good at arranging atoms in patterns with a scanning tunneling microscope (STM), as was famously done by IBM to demonstrate STM technology, and making "quantum corals" that demonstrate the wave-like properties of electrons. If nanomachines are built, they will work much more like the currently-known nanomachines — antibodies and proteins and so forth, restricted to catalysing only one family of reactions — and more complicated nanomachines will be closer to the size of biological cells.
Mechanical nanocomputers are theoretically possible, and research is steadily getting there. So far there's a 300nm electromechanical reed relay gate and an inverter that runs at 500kHz. The application is for environments that would trash electronics, e.g. high temperatures. For comparison, current computers' electronic transistors are on the order of 22nm (as of 2012) and mainstream consumer computer chips run at between 1GHz and 4GHz or so.
It should be noted that there are examples of self-replicating machines that dig into the ground and vacuum up the atmosphere. They sense the available resources of the surrounding territory and assemble useful products, even erecting mini solar panels to assist the process as well as producing the next generation of their initial seeding mechanism, all fully automated and largely unattended. They are called things like "tomato plants".
Nano-sized particles (<100 nm) have been used in consumer products, including clothing, electronics and cosmetics and food, for at least two decades. The safety of nanoparticles in food is not well understood, and is still being investigated, though modest amounts are believed to be safe. In the US, nanoparticles in food are currently regulated the same as any chemical additive. Titanium dioxide, silicon dioxide and zinc oxide are currently the most common nanoparticles added to food.
Nanotechnology as an idea doesn't have any problems per se, particularly as nanotechnology that does have problems doesn't exist. However, there are problems with some of the public depictions or expectations of nanotechnology, especially if Drexler-style nanotech is portrayed as "just around the corner" instead of part of the abstract sci-fi realm along with things like anti-gravity.
The main practical problem with nanotechnology is the phrase being overused as funding hype for what anyone else would call material science or synthetic biology.
Nanoparticles (asbestos fibres happen to be an example) can be hazardous as they are small enough to penetrate cell walls. This particularly applies to fibres — a cell ingests a fibre by its pointy end, reacting as if the fibre is an object of comparable size to its diameter… then more or less skewers itself on the fibre. There are activist groups worrying about this sort of thing, with varying degrees of scientific competence.
- ↑ 1.0 1.1 Nano-nonsense: 25 years of charlatanry (Scott Locklin, Locklin on science blog, August 25th 2010)
- ↑ Richard P. Feynman (December 1959) "Plenty of Room at the Bottom"
- ↑ Original thesis PDF.
- ↑ Let the Nanotech Wars Begin! (KurzweilAI, 14 December 2003)
- ↑ What is Zettatechnology? (A to Z of Nanotechnology)
- ↑ http://hplusmagazine.com/2011/11/30/exploratory-engineering-and-radical-abundance-an-exclusive-interview-with-dr-eric-drexler/
- ↑ Rupturing The Nanotech Rapture: Biological nanobots could repair and improve the human body, but they'll be more bio than bot Richard A.L. Jones, IEEE Spectrum, June 2008
- ↑ http://www.longecity.org/forum/topic/10070-guidelines-for-nanotech/#entry103806
- ↑ Cryonicists' sunk costs reasoning about Drexler's "nanotech." (Mark Plus, The Life of Man Qua Man on Earth blog, 2010-08-31)
- ↑ Total Annihilation: "It would have been too complex and time consuming to have little guys with hammers and scaffolds every time something was built in the game. It also wasn't futuristic enough. We needed something like magic, but with a thin veneer of science around it. Nanotechnology to the rescue!"
- ↑ T-X[wp]
- ↑ http://memory-alpha.org/en/wiki/Assimilation
- ↑ The Day the Earth Stood Still (2008 film)[wp], G.I. Joe: The Rise of Cobra[wp], etc.
- ↑ For example, the Replicators in Stargate
- ↑ http://nanotechweb.org/cws/article/indepth/19648
- ↑ http://www.crnano.org/BD-Goo.htm
- ↑ Babbage nanomachine promises low-energy computing (New Scientist #2573, 25 March 2010)
- ↑ Diego N. Guerra, Adi R. Bulsara, William L. Ditto, Sudeshna Sinha, K. Murali and P. Mohanty, A Noise-Assisted Reprogrammable Nanomechanical Logic Gate. Nano Letters, 10 March 2010, DOI: 10.1021/nl9034175
- ↑ http://www.newscientist.com/article/dn19440-steampunk-chip-takes-the-heat.html
- ↑ This Is the Future of the Fight Against Cancer (Janet Fang, Nature, 21 March 2010 doi:10.1038/news.2010.138)
- ↑ Nanoparticles in foods raise safety questions: These microadditives enhance color, flavor and freshness. But what do they do in the body? by Susan Gaidos (1:28pm, October 16, 2015) Science News.
- ↑ e.g. http://www.wisegeek.com/what-are-the-possible-dangers-of-nanotechnology.htm