High stable self-cleaning surface developed by monolithic hierarchical roughness

Many hierarchical structures are used to create self-cleaning capability. The stability and durability of superhydrophobic surfaces are still questionable in various applications. In this article, the effect of annealing process and wax-coating approach was considered to create nanostructures on micro-rice-like patterns. The morphology of resultant structures was analysed by FE-SEM and AFM instruments. The presence of nanostructures significantly increased contact angles on the hydrophobic surfaces (from 138 degrees to 158 degrees in the annealed process and to 161 degrees in the wax-coating method). The decreased sliding angle from 60 degrees in smooth surface to 10 degrees and 6 degrees in both superhydrophobic surfaces demonstrated a clear correlation between hierarchical structures and self-cleaning capability. From comparison, the monolithic pattern showed higher stable contact angle during 6 months period at room temperature, higher durable self-cleaning capability, good brushing and tapping resistance. Hence this approach would offer additional insights for developing self-cleaning characteristics.