Fabrication and Evaluation of Hierarchical Superhydrophobic and Salvinia Surfaces

We report an effective process to fabricate high-performance hierarchical superhydrophobic (SHPo) surfaces and a simple additional process to turn them into hierarchical Salvinia surfaces. The hierarchical roughness is obtained by creating microstructures, coating them conformally with alumina, and converting the coated alumina into nano-grass. The hierarchical roughness becomes SHPo after coating a fluorosilane self-assembled monolayer. Additionally, if desired, the hierarchical SHPo surface can be converted to a hierarchical Salvinia surface by applying polydopamine only to the top regions of the microstructures. Using a camera system designed to directly visualize the menisci on cleaved surfaces in water, we confirmed an increased plastron stability under negative hydrostatic pressure on the converted Salvinia surface compared to the SHPo surface with the same hierarchical roughness.