Harvesting Energy from the Sun
Rising oil prices and the threat of global warming have rekindled the search for alternative sources of energy. While we reported this year on the growing acceptance of nuclear power as a source of clean energy, we also described several advances in nanotechnology that may pave the way for more practical solar power. Konarka of Lowell, MA, has pushed forward its "roll-to-roll" solar cell technology, which is based on nanoparticles embedded in a film. While its cells aren't as efficient as conventional ones, they are made using an inexpensive process. The lower price tag, combined with the cells' flexibility, could make solar power available in more places, including the windows of buildings and fabrics for tents, handbags, and other items. We also reported on the use of nanowires for capturing the energy of the sun, which could lead to higher efficiency from inexpensive cells.

The Lithium Economy
Light lithium-based batteries can pack quite a punch -- so much so that they've been too dangerous to group together in high-power applications, such as cordless drills and hybrid cars. Now, thanks to computer modeling that identifies promising new battery materials, this is no longer the case. This year we saw the introduction of lithium ion battery packs in cordless tools, and 2006 will bring more such applications, as well as a move toward lighter, more powerful hybrid cars. Eventually, materials monitoring could lead to batteries with enough power and energy density to make electric cars practical -- and a pleasure to drive. Because lithium batteries don't have the distribution problems inherent in hydrogen, batteries could beat out fuel cells in the cars of the future.

Toward Self-Assembling Devices
A nanotech dream is the "one-pot" synthesis: combine raw materials, mix, bake -- and out comes a working device made from nanoscale parts. Such a synthesis technique wouldn't require as much energy as the high-temperature reactions in the semiconductor industry today. It would also dramatically cut down on the use of dangerous solvents and the production of waste materials. And it would also be cheap. Angela Belcher at MIT is directing the evolution of viruses and yeasts to make such self-assembly possible. Others hope to use diatoms as templates for nanodevices. In our current Technology Review magazine (Dec. 2005/Jan. 2006) we describe a nanomachine that could help assemble single-molecule memory devices.

Nanomedicine
This year saw the advance of fantastically sensitive nanosensors capable of detecting disease at its earliest stages -- when it can still be treated. Charles Lieber and Xiaowei Zhuang, chemistry professors at Harvard, demonstrated that nanowires could be used to detect a single viral particle. An array of such detectors might be able to screen almost instantly for as many as one hundred different viruses at once -- a boon for doctors diagnosing disease or a country defending against biological attacks.