Superhydrophobic Coatings from Ecofriendly Materials and Processes: A Review

So far, scientists have successfully mimicked superhydrophobicity based on careful observation and study of such surfaces found in nature. The key outcome is the fact that water-repellent plant or insect surfaces have unique hierarchical scale texture. Embedded in such textures, existence of unique waxy protrusions or structures is also found which can easily trap air underneath water droplets. Today, researchers can duplicate such surface textures and render them more sophisticated with advanced nanofabrication, lithographic, and wet chemistry techniques. In doing so, synthetic materials having very low affinity to water are extensively utilized. Among them, perfluorinated compounds pose some environmental concerns. Moreover, most of the superhydrophobic coating formulations and processing are deemed not ecofriendly enough to sustain large-scale fabrication or prohibitively expensive to transform into a standard industrial practice. Recently, however, significant efforts are made to fabricate superhydrophobic coatings by using natural materials and sustainable processes with lower potential environmental footprint. This review introduces, reviews, and discusses such advances, their performance compared to conventional ones while acknowledging the challenges and stressing the need to dedicate more resources to develop robust and long-lasting superhydrophobic coatings originating from intelligent processing of natural materials or synthetic biodegradables with ecofriendly technologies.