Big news on a very small scale
Advances in nanotechnology bring blessings as well as warnings of possible hazards. Two breakthroughs reported this month show how significant the blessings can be. One promises to become the first major alternative to chemical batteries in 200 years. The other opens a way to boost solar-cell efficiency.
A third development deals with the dark side. It offers a way to look into plant or animal cells to see if the molecule-size nanotech units that bring the blessings may also be doing mischief inside the basic units of biological life.
The promised devices are assembled from particles, tubes, or filaments that measure just 100 billionths of a meter (100 nanometers) in at least one of their dimensions. At that size, the material of which these units are made - carbon or a metal, for example - has most of its atoms on its surface. It is much more active chemically or electrically than is the same material in bulk form, where most of the atoms are buried inside. This activity is what gives devices assembled from such nanotech units their technological edge - and their potential toxicity.
Conventional solar cells, for example, are made from thin wafers cut from blocks of silicon. Building the cells as assemblies of nanotech units is a better way to boost solar-cell efficiency, says Craig Grimes, an engineering professor at Pennsylvania State University. His research team builds cells as molecule-size arrays of titanium. These titania nanotubes are covered with a dye that converts light energy to energy of electrons. The tubes channel the electron flow to form the cell current - electric power.
Meanwhile, at the Massachusetts Institute of Technology, Joel Schindall is developing what an MIT announcement calls the first "viable alternative to conventional batteries in more than 200 years." Instead of storing electrical energy in chemical form, Dr. Schindall stores it as the energy of an electrical field in a capacitor - a device widely used in electrical equipment. His group uses carbon nanotubes measuring just 1/30,000th the diameter of a human hair. The tubes are 100,000 times as long as they are wide. Assemblies of these nanotube capacitors could provide "energy storage densities comparable to batteries," Schindall says. Such devices would withstand temperature change or mechanical shocks far better than batteries do today.
Meanwhile, a review of nanotechnology's potential hazards published in the Feb. 3 issue of Science concludes that ways to check for environmental dangers are "urgently required." One way is by examining plant and animal cells and using them as monitors, said Thomas Weber of the Pacific Northwest National Laboratory in Richland, Wash., at a session of the American Association for the Advancement of Science in St. Louis on Friday. His group is developing a way to use infrared light to see inside living cells and detect signs of nanoparticle contamination. It would be a powerful way to watch for trouble as nanotechnology permeates the global economy.
An estimated $13 billion worth of nanotech-based products - including paints and cosmetics - were sold globally in 2004. Some projections expect that to grow to several trillion dollars' worth of products by 2014. It's an explosive development that affects the entire planet.
