Ralph Nuzzo is a University of Illinois professor of chemistry who wants to use soft lithography instead of conventional photolithography for fabricating transistors on curved surfaces. He says the desire for a new patterning process is driven by the need to fabricate components over large formats with unconventional materials. Soft lithography is better for component fabrication on curved surfaces because the process is compliant and conforms to small surface irregularities. Soft lithography patterning techniques, such as micron-scale polymer molding, require that the mold be flexible enough to conform to the curvature of the substrate, but stiff enough to preserve the integrity of the pattern. Fabricating microstructures on spherically curved substrates required depositing thin films of aluminum, silicon, and silicon nitride. When the mold contacted the substrate, Nuzzo flowed polyurethane into the mold, cured it, and peeled away the mold. The resulting polyurethane pattern on the substrate measured 30 microns. Thin-film arrays deposited on spherically curved substrates have potential applications in optical detectors for taking pictures over a wide field of view. Contact Nuzzo at (217) 244-0809 or e-mail email@example.com.
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