Designing robust underwater superoleophobic microstructures on copper substrates

Recently, surfaces with a robust underwater superoleophobicity have attracted much attention. Although it is recognized that stable microstructures are significant for such surfaces, a clear picture of how microstructural features such as morphology, size, etc. influence their own stability and related wettability is still missing. Herein, three low adhesive underwater superoleophobic copper surfaces with different microstructures (hemispheric, pinecone-like, and honeycomb) were first prepared, and then the stability of these microstructures was examined by a series of physical and chemical damage experiments (sand grain abrasion, corrosion in acid/base solutions, etc.). The results indicate that the hemispheric microstructure is more stable than the other two microstructures and the corresponding surface has a robust underwater superoleophobicity. Theoretical simulation analysis further confirms the experimental results and reveals that different stabilities are ascribed to different stress distributions on these microstructures under an external force due to distinct microstructure shapes. Furthermore, based on the same design strategy, a robust underwater superoleophobic oil/water separation copper mesh film was also prepared. This work provides an insight into the effect of microstructural features on the stability and related underwater oil-repellent properties of superoleophobic copper surfaces, and could provide us with some fresh design ideas for robust superwetting surfaces.