For 5,000 years the only way to shape metal has been by the "heat and beat" technique. Even with modern nanotechnology, metalworking involves carving metals with electron beams or etching them with acid.
Now Cornell researchers have developed a method to self-assemble metals into complex configurations with structural details about 100 times smaller than a bacterial cell by guiding metal particles into the desired form using soft polymers.
"I think this is ingenious work that takes the fundamental concepts of polymer science and applies them to make metals in a totally novel way," said Andrew Lovinger, the director of the Polymers Program at the National Science Foundation. "In so doing, it opens the door to all kinds of new possibilities."
Applications include making more efficient and cheaper catalysts for fuel cells and industrial processes, and creating "plasmonic" surface structures capable of carrying more information across microchips than conventional wires do.
"The polymer community has tried to do this for almost 20 years," said Uli Wiesner, Cornell professor of materials science and engineering, who reports on the new method in the June 27, 2008, issue of the journal Science. "But metals have a tendency to cluster into uncontrolled structures."
Wiesner's research team has now developed a method to overcome this globby inclination of metals. First, metal nanoparticles measuring about 2 nanometers (nm) or 10-20 atoms in diameter, are coated with an organic material known as a ligand. The ligands form thin jackets around the metal atoms, changing their surface chemistry. Keeping the ligand jackets thinly tailored is a key factor that permits the volume of metal in the final structure to be large enough to hold its shape when the organic materials are eventually removed.
The jacketed metal atoms are then put in a solution containing block co-polymers, a kind of nano-scaffolding materi
|Contact: Lisa-Joy Zgorski|
National Science Foundation