Dynamic Interference Colors in Electrospun Microfibrous Mats

The design of soft materials that change their optical properties in response to a variety of external stimuli is one step toward mimicking the dynamic color changing systems that are observed in nature. A simple, multiresponsive system is presented where the colors of core/sheath microfibers and microfibrous mats can be tuned by confinement (i.e., fiber diameter), temperature, and UV-vis irradiation. Microfibers are fabricated using coaxial electrospinning with a nematic liquid crystal core and a polymer sheath. This results in soft, flexible mats of material that display uniform color when viewed between crossed-polarizers both under a microscope and by the naked eye. The observed interference color is dictated by the inner fiber diameter and the birefringence of the liquid crystal core. While the fiber diameter is set during mat fabrication, continuous in situ color change by tuning the birefringence of the liquid crystal is demonstrated using temperature or photochemical control of azobenzene-based surfactants embedded in the polymer sheath. The expected colors are calculated and easy-to-use color charts are generated to accurately predict fiber behavior.