Plastic fantastic

Dr. Yueh-Lin (Lynn) Loo at The University of Texas at Austin has received a 2005 Young Investigator Award from the Arnold and Mabel Beckman Foundation to find ways to improve the ability of polyaniline to conduct electricity.

Loo, an assistant professor of chemical engineering, will use the three-year, $264,000 award to seek a 10-fold increase in the conductive ability of the plastic.

That enhancement might be enough for manufacturers to begin considering polyaniline-based wires for products that include: electronic display screens that can be rolled up after use, clothing with polyaniline woven into it that changes colour when exposed to a harmful chemical, and implantable medical devices that release a drug when someone’s body temperature changes.

“Using this material to develop biodevices would be especially nice,” Loo said, “because polyaniline appears to interact well with living cells.”

To make the polyaniline electrically conductive, Loo’s has developed a new technique in which a polymeric acid is added to the polyaniline. Determining the optimum ratio of the two starting components needed to achieve the best conductivity will be part of Loo’s efforts.

Previous attempts to dope polyaniline to become conductive failed because the final product would not dissolve in any solvents, which is considered crucial if inexpensive products are to be made from the material. But using polymeric acid actually increases polyaniline’s ability to dissolve in water.

Dr. Yueh-Lin (Lynn) Loo, assistant professor of chemical engineering, displays a pliable sheet with printed polyanaline wires and interconnects

Loo plans to find the right ratio of polymeric acid to mix with the plastic so that an excess of the acid will be present along the polyaniline backbone. These extra acid molecules are thought to make polyaniline dissolve in water because they are available to interact with water molecules.

Loo has already moulded water-soluble polyaniline into wiring using a water-based process developed in her laboratory called the stamp-and-spin-cast technique. But, she notes that such polyaniline wiring would never conduct electricity as well as gold or other metals. Nor is it possible to create polyaniline at the nanoscale dimensions, or with the uniformity, needed for it to be considered for wiring in next-generation microprocessors.

The 10-fold enhanced conductivity she seeks, though, should suffice for the cheap, flexible, large-scale applications under consideration.