Nanowires
When shrunk to just a few nanometres in width, solid rods of silicon and other semiconductors take on astounding properties. Because of their ultra-skinny shape, nanowires are in effect 1-dimensional. The result is that electrons can only flow along the wire rather than across it, making them easy to control.
Nanowires make extremely fine sensors, able to detect noxious chemicals down to a few parts per billion; a single molecule binding to a nanowire will disturb the flow of electrons inside.
Nanowires are also highly efficient at converting waste heat to electricity, or acting as mini-coolers.
Buckyballs
Nanotech is improving our chances of harnessing alternative forms of energy. Take organic polymer-based photovolaic cells, which researchers have pursued for more than 15 years. These promise to be a much cheaper way of turning solar energy into electricity than traditional solar cells made from crystalline silicon. The problem is that polymers do so much less efficiently.
A well-known nanostructure has come to the rescue: the round, football-like carbon molecule known as a buckyball, or fullerene. When photons hit an organic solar cell, they knock electrons loose from the polymer, but these electrons tend to quickly recombine into the mix.
If you add buckyballs to the polymer, however, they grab the free electrons and relay them in the form of usable electricity.
Nanoparticles
The future of nanotech lies in coaxing molecules to assemble themselves into arbitrary shapes on demand. This could lead to all manner of molecular-scale devices being built automatically. Researchers from Northwestern University in Illinois and Brookhaven National Laboratory in New York have developed one of the most advanced approaches to date by controlling how nanoparticles bind to one another.
By equipping gold nanoparticles with tentacle-like strands of programmed DNA, they have shown for the first time that nanoparticles can link themselves up with their neighbours to form intricate and ordered 3D structures. Such a nano-assembler can create fundamental arrangements of molecules such as crystal lattices that could be used for catalysing chemical reactions, manipulating light or fighting disease within the body, for example. The researchers are already working on assembling more complex structures.
Mason Inman is a writer based in Massachusetts
