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“It has long been an axiom of mine that the little things are infinitely the most important.” —Sir Arthur Conan Doyle
Nanotechnology is the study of very small things, dealing with materials 100 nanometers or smaller in at least one dimension. One nanometer (nm) is one billionth of a meter. By comparison, the smallest bacteria are about 200 nm long; a human hair is approximately 80,000 nm wide, far beyond the nano range. However, if nanomaterials were just small versions of big things, they wouldn’t be particularly interesting. The exciting applications come because materials sometimes act in a fundamentally different way when their size shrinks to a minimum.
The scientific concept of nanotechnology was born in 1959 in a famous presentation by Richard Feynman, “There’s Plenty of Room at the Bottom.”1 Feynman talks about putting the Encyclopedia Britannica on the head of a pin, or making computers smaller than a building—1959 was a different world! But for all its antique quaintness, in his lecture, Feynman perceptibly realized, “At the atomic level, we have new kinds of forces and new kinds of possibilities, new kinds of effects.” He could not have been more prescient.
The prefix “nano” comes from the Latin nanus (dwarf), but the term “nanotechnology” was first used by K. Eric Drexler2 in his seminal 1986 book Engines of Creation: The Coming Era of Nanotechnology, available free online at e-drexler.com/p/06/00/EOC_Cover.html. Since its publication, there has been unceasing development of medical and cosmetic applications, and wide-ranging academic research. Cosmetic applications have concentrated on sunscreens, hair treatment and antiaging products.
Nanosized zinc oxide (ZnO) and titanium dioxide (TiO2) for sunscreens were the first, and still most important, applications of nanotechnology in personal care. The classic visual of macro TiO2 is a lifeguard with a white nose. By reducing the particle size below one fourth the wavelength of light, zinc oxide and titanium dioxide become invisible while completely maintaining their sun protectant properties. If anything, the smaller particle size enhances protection by fitting into small irregularities in the skin.