Buffalo, NY--A new polymer grating developed by engineers at the University at Buffalo (UB), The State University of New York, is rainbow colored when viewed from a single perspective, reflecting many different wavelengths of light. The polymer is fabricated in a one-step, low-cost method and could be used as a filter for handheld multispectral imaging devices that identify the "true color" of objects examined.

"The ease of producing the polymer could make it feasible to develop small devices that connect with cell phones to conduct multispectral imaging," said Qiaoqiang Gan, a UB assistant professor of electrical engineering and another member of the research team. "Our method is pretty low-cost, and because of this and the potential cell phone applications, we feel there is a huge market for improving clinical imaging in developing countries," Gan said.

The rainbow colors appear due to the surface geometry of the filter, and not by pigments; the same biomimetic principle that colors the wings of butterflies and peacock feathers. The work was reported on online Feb. 22 in Advanced Materials. The UB Office of Science, Technology Transfer and Economic Outreach (STOR) has submitted a provisional patent application detailing the production process to the U.S. Patent and Trademark Office.

To create the rainbow material, the creators sandwiched a photosensitive pre-polymer syrup between two glass slides. Next, they directed a laser beam through a curved lens placed above the pre-polymer solution. The lens divided and bent the laser beam into light of continuously varying wavelengths. As this light hits the solution, monomers in the solution began joining into polymers, forming a continuous pattern of ridge-like polymer structures. The resulting structure is a thin filter that is rainbow-colored when viewed under white light. The filter the researchers created was about 25 mm long, but the technique they used is scalable and different sized filters can be fabricated.

SOURCE: University at Buffalo; www.buffalo.edu/news/13214

IMAGE: A rainbow-colored grating, about 25 mm wide, is shown under sunlight. Enlarged microscope images show the graded surface, with the black bars indicating a length of 10 microns. (Courtesy University at Buffalo)