New Method Sticks Metals to Teflon, Leaves Nonstick Surface Intact, Science Paper Reports

BUFFALO, N.Y. -- Never willing to leave well enough alone, scientists have long tried to get things to stick to Teflon. From electronics to biomedicine, a nonstick material that was sticky in some places would have tremendous applications. But any method that seemed to work ended up destroying the surface.

This week, a paper in Science by chemists at the University at Buffalo, Naval Research Laboratory and Geo-Centers, Inc. describes the first process that lets scientists deposit metals on nonstick surfaces while leaving the surface intact. The simple and inexpensive process is expected to greatly expand the use of Teflon and other fluoropolymers in electronic and biomedical applications.

Joseph A. Gardella, Ph.D., professor of chemistry at UB and Terrence G. Vargo, Ph.D., research fellow at UB, have developed patented processes for modifying fluoropolymer surfaces with specific chemistries. These materials have been utilized for fundamental studies of neural cell attachment and growth. The long-range goal of this work is to develop materials for supporting and directing the growth of neural tissue for potential use in biomedical implants.

Researchers at the Center for Bio/Molecular Science and Engineering at NRL have concurrently been using similar chemistries on various surfaces, such as silicon and glass, to produce well-defined patterns of conducting metal pathways via patented electroless metallization processes. These processes utilize metal-binding sites, which allow metals to grow on a surface from a water solution.

These two separately developed concepts have now been combined to produce a method for applying metals to Teflon, either homogeneously or in specific patterns.

The new process, the first to be able to do that, has attracted the attention of the Shipley Corp., a major manufacturer of microelectronic chemicals and technologies that has partially funded the work.

"This effort between government and university laboratories serves as a paradigm for collaborative basic research leading to technology transfer and applications in industry," said Jeffrey M. Calvert, Ph.D. leader of the Surfaces and Interfaces Group at the Center for Bio/Molecular Science and Engineering at NRL and co-author of the Science article.

"One of the substrates expected to be of great importance in the future for microelectronics packaging is Teflon," said Calvert. "But to use it effectively, you have to be able to define adherent metal patterns on those surfaces."

"Fluoropolymers are incredibly successful materials because of inherent properties, such as their insulating character, and the fact that they're chemically unreactive and very few things adhere to them," said Gardella. "But in order to use them for thin film or surface applications, it was necessary for us to change the surface chemistry. Until now, that has only been possible with extremely corrosive and expensive methods.

"Most people have produced reactions on nonstick surfaces by stripping off all of the fluorine, turning it into graphite, essentially, and sticking some hydroxyls on," said Gardella. "What we did was to take just a few fluorines off. It turns out that leaving on some fluorine makes the hydroxyls even more reactive."

The NRL catalyst is designed to bind directly to metal-binding sites controllably placed on the modified fluoropolymer surface, such as Teflon. The metal then is deposited on the surface through immersion in a metal plating bath, an extremely common industrial technology.