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One application of nanotechnology is the development of so-called smart materials . This term refers to any sort of material designed and engineered at the nanometre scale to perform a specific task, and encompasses a wide variety of possible commercial applications. One example is materials designed to respond differently to various molecules; such a capability could lead, for example, to artificial drugs which would recognize and render inert specific viruses. Another is the idea of self-healing structures, which would repair small tears in a surface naturally in the same way as self-sealing tires or human skin; and while this technology is relatively new, it is already seeing commercial application in various engineering plastics.
A nanosensor would resemble a smart material, involving a small component within a larger machine that would react to its environment and change in some fundamental, intentional way. As a very simple example: a photosensor could passively measure the incident light and discharge its absorbed energy as electricity when the light passes above or below a specified threshold, sending a signal to a larger machine. Such a sensor would cost less and use less power than a conventional sensor, and yet function usefully in all the same applications — for example, turning on parking lot lights when it gets dark.
While smart materials and nanosensors both exemplify useful applications of nanotechnology, they pale in comparison with the complexity of the technology most popularly associated with the term: the replicating nanorobot.
The idea of molecular manufacturing is popularly linked with the idea of swarms of coordinated nanoscale robots working to build things. This concept, introduced by Drexler in his 1986 book, Engines of Creation, was augmented in his 1992 book Nanosystems: Molecular Machinery, Manufacturing, and Computation with approaches involving macroscopic factories using fixed nanoscale productive machinery. Serious technical work has continued on both approaches, but the "replicating nanorobot" idea remains prominent in popular discussions of the subject.
In the fourth chapter of Engines of Creation', Drexler introduced von Neumann's idea of machine self-replication into the discussion of nanotechnology. Cells build copies of themselves in order to reproduce, and (unless life is genuinely magic) human-designed molecular machine systems could do likewise. If a molecular nanorobot could construct copies of itself from basic raw materials such as acetylene or butane, building diamondoid structures, then once the first such robot was constructed any desired quantity could be obtained quite quickly and at very low cost. (Self replication is, of course, not the only way in which machines can build more machines.)
These same generally-capable robots, called assemblers, could then build more special-purpose objects that humans would find directly useful: houses, kitchen widgetWidget is a general-purpose term for any unspecified device, including those that have not yet been invented. It is commonly used in textbook and other examples where the identity of the product or function is irrelevant and could be distracting: studentss, carsAn automobile usually called a car (an old word for carriage) or a truck is a wheeled vehicle that carries its own engine. Older terms include horseless carriage and motor car with "motor" referring to what is now usually called the engine. The act of ope, furnitureFurniture is the collective term for the movable objects which support the human body (seating furniture and beds), provide storage, and hold objects on horizontal surfaces above the ground. Storage furniture is used to hold or contain smaller objects suc, medical instrumentsNanomedicine is the medical application of nanotechnology and related research. It covers areas such as nanoparticle drug delivery and possible future applications of molecular nanotechnology (MNT). The first thorough analysis of possible applications of, spaceships, etc. Like the assemblers themselves, these products would cost considerably less than those produced today. Specifically, any such manufacturing process would have as inputs raw materials, energyThis article is about the scientific concept. Energy use by humans is discussed in other articles''. Energy generally and qualitatively speaking, is the property (or the quantity of the property) of doing things or supplying power. The expressions energy, design software, and time. For less speculative discussion of this potential, see the separate article on the molecular assembler.
However, critics doubt the feasibility of controllable self-replicating nanobots: they cite the possibility of mutations removing any control and favoring reproduction of mutant pathogenic variations. Advocates counter that bacteria are (of necessity) evolved to evolve, while nanobot mutation can be actively prevented by common error-correcting techniques used in computers today. They also note that (1) self-replicating machines capable of replication outside of a restricted factory environment do not form a necessary part of a productive nanotechnology, (2) the process of self-replication can be made inherently safe, and (3) free-foraging replicators are in fact absent from current plans for developing and using molecular manufacturing. Research in this area has included the development of simulation software, such as NanoCAD.