Microstructured rubber and its wettability

Microstructured surfaces have been attracting a considerable amount of attention for many practical applications, such as superhydrophobic materials. The key issue in everyday applications of superhydrophobic materials based on microstructured surfaces is their durability because most microstructures are prepared with stiff and fragile materials and are easily broken mechanically. In this study, we focused on vulcanized rubber as a flexible and durable hydrophobic material for the fabrication of microstructured surfaces. Superhydrophobic spiky microstructures were simply prepared from vulcanized rubber by using a silicon micromold and compact hot-press equipment. Owing to the elasticity of the vulcanized rubber, the spike-array arrangements on the rubber surface were reversibly deformed by repeated stretching without destruction of the spiky microstructures. Surface wettability was affected by the spike-array arrangements, which can be controlled by stretching concomitantly with the degree of elongation. This phenomenon was theoretically explained by the wettability transition from a Cassie–Baxter to a Wenzel state considering water penetration into the gaps among the spiky microstructures. The results indicated that microstructured vulcanized rubber surfaces can be applicable to a wide variety of fields because of the superior functions derived from their microstructures.