Tiny tubes might help solve one of the world's largest problems-an ample supply of fresh water. A physicist at Boston College is teaming up with an independent inventor to use carbon pipes only a few nanometers (billionths of a meter) across as a fast and energy-efficient means of water desalination. Key to the work is BC professor Zhifeng Ren's discovery of a way to fabricate the tubes as an extremely well-aligned nano "forest."

The nanotubes are electrically charged, and when saltwater runs through them, sodium and chloride ions are electrostatically adsorbed onto the tube surfaces; rapidly removing the charge releases the ions into a waste stream. Because of the nanotubes' high electrical conductivity and large surface areas relative to their volume, they are far more efficient in ridding the water of salt than, say, ordinary carbon. The research is funded by the Defense Advanced Research Projects Agency, which wants to develop a portable, energy-efficient desalination unit. Ren and Mark Andelman, president of Worcester, Mass.-based Biosources, expect to build a prototype this winter.