Photonic Shape Memory Chiral Nematic Polymer Coatings with Changing Surface Topography and Color

The fabrication of shape memory coatings that change both reflectivity and topography is hampered by the lack of facile methods and materials. Now, shape memory photonic coatings are fabricated by high-speed flexographic printing and UV-curing in air of a chiral nematic liquid crystal ink. Deformable polymeric films with a red reflection band and a smooth surface topography are obtained which can be thermally programmed above room temperature by using a rough stamp. This thermomechanical programming results in a temporary rough surface topography leading to surface scattering and as a result a gray color below room temperature. By heating the coatings, a shape recovery to the permanent state is observed, thereby restoring the smooth surface topography and the iridescent red reflection color. It is shown that this recovery is highly temperature dependent, which allows for a fast and distinct optical and topography change upon exceeding room temperature. These thermoresponsive photonic crystal coatings have a great potential as low-cost optical sensors, smart adhesives, and adaptive biosurfaces.