Effects of trace organic contamination on micro–nanostructure-induced superhydrophobic properties

Superhydrophobicity has been a crucial research topic due to its ability to make surfaces stay dry and self-clean. Low-surface-energy organic coatings are widely used to fabricate superhydrophobic surfaces by modifying surface groups and minimizing surface energy. Considering defects would seriously undermine these coatings, which would further lead to hydrophobicity dwindling and lifetime decreasing, researchers have begun to investigate the development of superhydrophobic surfaces without organic coatings. However, it is still controversial whether these superhydrophobic surfaces are really free of organic substances with low surface energy. In this work, O₃ bombardment was utilized to construct micro–nanostructures on aluminum foil. The aluminum foil surface turns to superhydrophobic after ozone bombardment with the contact angle (CAs) increasing from 20° to 161°. Results showed the presence of silicon contaminations on alumina surfaces despite the fact that no organic coatings are utilized in the fabrication process. The transition of hydrophilic-to-superhydrophobic was attributed to both surface morphology and silicon contamination from pump oil. Our work reveals that trace organic contamination from pump oil is a key factor that cannot be ignored in scenarios with vacuum pump use, which could provide some favorable evidence to figure out the controversial issue mentioned above. Graphical abstract: [Figure not available: see fulltext.]