Polymer replica of microcrystalline surface with dual wettability, mimicking a termite wing

Abstract

Termite wings are covered with hair shafts and micrasters, which provide it with dual wettability. Although the surface is superhydrophobic for bulk water and large droplets, it is adhesive for microdroplets of water. We mimicked this rough surface by applying a photoinduced crystal growth phenomenon on a photoreactive crystalline surface consisting of two photochromic diarylethene derivatives. This crystalline surface showed dual wettability, but the photoreactive crystalline system was not applicable under daylight. This lack of applicability was apparent because the rough crystalline structures on the surface melted under visible light irradiation. We used soft lithography and transcribed the rough structure of the crystalline film to a stable polycycloolefin polymer (ZEONEX 480) surface. In this case, ultrasonic treatment was indispensable for molding complex structured surfaces. The transcribed surface showed the same characteristics of dual wettability as the crystalline surface. The crystalline surface using two photochromic diarylethenes was prepared to mimic a termite wing showing dual wettability. The surface is useful to correct small water droplets in the air. However, the crystalline system was not applicable for the use because crystalline structures on the surface melt under daylight. We copied the rough structure of crystalline film to a stable polycycloolefin polymer (Zeonex 480) surface. The copied surface showed the dual wettability as same as that of the crystalline surface.