PRINCETON, N.J. -- Princeton researchers have created ultrasmall plastic structures with a method that is cheaper and more versatile than previous techniques. The discovery has yielded surprising insights into the behavior of materials at very small scales, while spawning many basic research questions. It also could pave the way to a new generation of miniature products, from computer memory chips and video components to devices for sorting DNA molecules.
Professor of electrical engineering Stephen Chou and graduate student Larry Zhuang found that they could coax a flat sheet of plastic resin to assemble itself into a minute, perfectly ordered array of pillars -- with remarkably little specialized equipment. The pillars are a little more than half a micron (a millionth of a meter) in height and width. Viewing one of these pillars next to the head of a pin is like looking at a stack of about 15 quarters next to the dome of the U.S. Capitol. Chou expects that refinements of the technique will yield even smaller structures.
The researchers discovered the technique accidentally while working on another nano-fabrication process called imprinting. In that process, also invented by Chou, a pattern, or mask, is pressed into soft plastic polymer, like pressing minute fingers into wet plaster. The researchers were pressing a mask into polymer when dust prevented the two pieces from coming together. Afterwards, when they examined the polymer, they found that it contained a pattern of pillars even though the mask never touched it. Not only had the pillars grown by themselves, they had arranged themselves into a perfectly ordered array.
"It was a very surprising discovery," says Chou. "No one had ever seen such a thing."
Suddenly Chou had an entirely new production technique: simply bring the two pieces close together and let the pattern assemble itself. He dubbed the new approach LISA, for Lithographically I
Contact: Steven Schultz