Scientists developing devices for optical and electronic applications may get a boost from a new process for cutting three-dimensional (3-D) arrays of holes in a polymer material. Mohan Srinivasarao of the Georgia Institute of Technology (Atlanta, GA) has found a way to create an orderly pattern of air bubbles throughout a polymer film using a simple solvent. By controlling the polymer, solvent, humidity, and flow of air across the polymer, he triggers the condensation of tiny uniform water droplets. The droplets sink into the polymer film. The process repeats itself on its own until the film is filled with a 3-D array of water bubbles. When the solvent and water evaporate, they leave behind a polymer scaffold with a lattice of equal-size air bubbles.
"The beauty of this process lies in its simplicity," says Andrew Lovinger, director of the polymers program at the National Science Foundation (NSF; Washington, DC), which funded the work. "You just let the solvent evaporate at room temperature and in a few seconds you get these beautiful honeycombed polymer films."
"This represents an easy way of making materials with the regular structure needed for optoelectronics applications," said Srinivasarao. "This is also a self-assembly process." He reports on the results in the April 6 issue of Science. If the process is shown to be usable in developing photonic bandgaps or photonic crystals, it could contribute to the development of optical switches and the ability to direct or steer light beams, just as electrical switches and conducting materials control and direct electrical current. Potential applications include lasers, antennas, millimeter wave devices, and solar cells.
Srinivasarao, a physical polymer chemist in Georgia Tech's textiles and fiber engineering department, is an NSF CAREER awardee. The CAREER program provides financial support to young investigators during the early years of their faculty positions. According to Lovinger, the program emphasizes not only first-rate research, but also "educational commitment and innovation." As part of his educational outreach, Srinivasarao organized several workshops sponsored by NSF and Exxon Corp. for high-school science teachers on Polymers in Everyday Life.