Nanomachines are very small machines, the dimensions or components of which are measured in nanometers. A nanomachine may be larger than 1,000 nanometers, but usually no larger than 10,000 nanometers (10 microns). Designing and fabricating nanomachines is a goal in the large and well-funded discipline of nanotechnology, though many workers in nanotechnology take the less ambitious route of designing passive nanoscale materials. A nanomachine refers to an active, functioning system with nanoscale components.
The human body is filled with nanomachines, arguably making up most of its mass. A cell might be considered a nanomachine because it consists of nanoscale components. An even more obvious nanomachine would be ribosomes, molecular factories that synthesize proteins. Ribosomes are about 20 nanometers in diameter. Other biological nanomachines would be bacteria and viruses.
Currently, nanomachines are still essentially in the research-and-development phase, though researchers are very hopeful for their long-term potential. One nanomachine, announced in April 2008 by researchers from the Nano Machine Center at the California NanoSystems Institute at UCLA, can releases anti-cancer drugs within the cell when activated by light. The machine, called a nanoimpeller, consists of mesoporous silica nanoparticles with its pores coated in azobenzene, a chemical that can switch between two different positions depending on exposure to light. The interior of the nanoimpeller was filled with an anti-cancer drug, then introduced into human cancer cells in culture, where they were coaxed by light exposure to release their payload. Varying the intensity and wavelength of the light gave the researchers precise control over their nanomachine.
Other interesting nanomachines have been built by Nadrian Seeman's lab at the New York University Department of Chemistry. Using DNA, Dr. Seeman has produced active grid arrays that alternate between configurations, and even a DNA "walker" that can move forward on molecular "legs." Seeman's lab has demonstrated the versatility of DNA as a building material for nanomachines.
Though nanomachines are just in the research stage, their largest long-term impact could be in the areas of manufacturing, medicine, and the military. If nanomachines could be coaxed into self-replicating, or could be built in large quantities using self-assembly, and programmed into cooperating to create objects, they could be formed into a custom manufacturing system with far more capabilities than anything in existence today. Such a hypothetical desktop device has been called a nanofactory.