The term nanotechnology gained popularity in the 1970s and 1980s, but technologies that use tiny or “nanosized” objects have been around for centuries. Hundreds of years before this modern term was coined, scientists were using the properties it describes to manufacture cutting-edge goods and to explore the world around them. Nanosized particles have recently been discovered in artifacts dating back to the 16th and 17th centuries, and Enlightenment-era nanoscience has influenced today’s advanced, high-tech research.
Medieval artisans discovered through alchemical experimentation that adding gold chloride to molten glass resulted in a red tint, and adding silver nitrate turned the glass yellow. The technique reached its height during the 16th through 18th century and resulted in some of the world’s most spectacular stained glass windows. Recently scientists analyzed stained glass from this era and discovered that the technique, possibly dating back to the 10th century, worked because of nanotechnology; analysis of the stained glass revealed that gold and silver nanoparticles, acting as quantum dots, reflected red and yellow light, respectively.
From the 12th to 18th century, Middle Eastern metalsmiths also practiced a form of nanotechnology. Using steel ingots imported from India, Damascene metalsmiths forged blades sharper and more durable than western blades, especially those of the Crusaders. The exact process for producing these highly prized blades remained a closely guarded trade secret, handed down only from teacher to apprentice. Scientists and historians have postulated that as Indian steel mines were depleted mining shifted elsewhere, and eventually the ingots no longer had the specific composition required to produce Damascus steel. Since the method no longer worked, it was lost through the ages. In 2006 materials scientists, using high-resolution transmission electron microscopy, found traces of carbon nanotubes and nanowires present in Damascus steel blades. They theorized that these nanowires, encapsulated by the carbon nanotubes, were responsible for Damascus steel’s legendary sharpness and durability.
In the late 19th and early 20th centuries, industrialists used carbon black, which has since been discovered to be a nanomaterial. At the turn of the century, scientists found that carbon black could reinforce rubber and thus improve its strength, tensile properties, and tear and abrasion resistance. Carbon black also increased the hardness of vulcanized natural rubber. Manufacturers soon applied this discovery commercially. In 1910 BFGoodrich began adding carbon black filler to extend the life span of its tires, and today virtually all automotive tires are reinforced with carbon black. Recently scientists have discovered that carbon black’s reinforcement properties can be attributed to the interaction between the rubber and the nanosized carbon particles’ grain.
In all of these cases manufacturers were unaware that they were using what we now call nanotechnology, and the scientific principles behind these technologies were not fully understood until much later. Nonetheless, if one looks closely at history there are cases in which the scientific theory was understood before the application was developed—a model that current nano–technologists and materials scientists emulate.
Scientists theorized that nanowires, encapsulated by carbon nanotubes in the blade, were responsible for Damascus steel’s legendary sharpness and durability.
In 1773 Benjamin Franklin wrote a letter to the English physician and chemist William Brownrigg that detailed his observations on the effects of oil on water. In his letter Franklin describes a voyage at sea on which he observed that greasy water dumped by the ship’s cooks had a calming effect on the ship’s wake. Franklin learned that the calming effect of oil on water was common seafarers’ knowledge, but no one really understood how it worked. After arriving on shore in London, the intrigued Franklin conducted an experiment on a windy day in a pond at Clapham Common. He deposited a teaspoon of oil at the edge of the pond where waves were forming and moving out toward the middle. The waves and wind spread the oil across the pond, and more than a square acre of turbulent water was quickly calmed. Even large leaves and twigs on the surface of the pond were pushed aside by the thin film of oil.
While similar observations were made as far back as Pliny the Elder, Franklin was the first to theorize this phenomenon using scientific principles. In his letter to Brownrigg, Franklin proposed that a mutual repulsion existed between water and oil particles. The repulsion’s force was so strong that it caused the oil to push itself away from the water and produce a widespread, nearly invisible film on top of the water.
Subsequent experiments by Lord Rayleigh, Irving Langmuir, and others confirmed that oil, floating above denser water, created a monolayer film only a few nanometers thick, revolutionizing surface science and providing the basis for thinfilm coating technologies that are now omnipresent in our everyday lives. In the 1920s Langmuir and Katherine Blodgett immersed a substrate into a solution, coating the substrate with a barium stearate film exactly one molecule thick. Now known as Langmuir–Blodgett films, this discovery allows scientists to create and deposit extremely precise thin films, and it is crucial in today’s cutting-edge study of monolayers in electrical engineering and materials science. After further experimentation Langmuir and Blodgett found that a thin film of 44 or 46 molecule layers can cancel out light reflection on natural glass. Today virtually all lenses requiring minimal reflections (camera or telescope lenses, for example) are coated with nonreflective thin films.
A fundamental difference between these historical examples of nanotechnology use is in the sequence of events. The technology used to produce stained glass, Damascus steel, and carbon black existed long before the scientific explanation was fully understood. But in the case of the monolayers of Franklin, Langmuir, and Blodgett the sequence is reversed: the scientific understanding was achieved long before any thin-film products made it to the market. Today nanoscientists are following the monolayer example, actively pursuing nanoscience research before attempting to harness their discoveries to produce nanotechnology.
Some efforts are close to or are already bearing fruit. Fabrics produced with nanotechnology are already on the market: waterproof fabrics are made by depositing fibers billions of nanometers long into natural cotton. These new fibers, called “nano-whiskers,” increase the surface tension of the fabric so drops of liquid cannot penetrate. At Rice University in Houston, Jennifer West and her colleagues have developed gold-silica nanoshells that are now in clinical trials as a cancer treatment. The nanoshells attach themselves to cancerous cells; once attached, the nanoshells can absorb enough infrared heat, when exposed to laser light, to kill the cells.
Industry is also putting considerable resources behind nanoscience research. Recently the Advanced Energy Consortium (AEC) began funding a project to use nanoparticles to aid in oil and gas recovery. The AEC, made up of companies including BP America, Conoco Phillips, and Halliburton Energy Services, are hoping to take advantage of the diminutive size of the nanoparticles to create detailed threedimensional maps of the structure of porous rock formations. Currently oil companies are able to extract only about 40% of crude oil from the oil or gas found in these reservoirs, but they hope that by penetrating these geological “sponges” with nanoparticles they can more accurately map the reservoirs and extract more.
While these more recent examples span textiles, medicine, and petroleum mining, they all depend on the practical application of nanoscale scientific principles first proven in a laboratory setting.
We are witnessing a transition from “nanotechnology toward nanoscience” to the current movement of nanoscience toward nanotechnology, but the line between the two is not distinct. In the future there will undoubtedly be more cases in which a phenomenon or product that was developed outside of a nanoscience framework will be discovered to be dependent on nanotechnology. But today, with so much public excitement and funding being directed toward nanoscience research, nanotechnology research programs will gravitate toward understanding small-scale science before ramping up into application.