Fast-response, no-pretreatment, and robustness air-water/oil amphibious superhydrophilic-superoleophobic surface for oil/water separation and oil-repellent fabrics

Surfaces with uniform and stable superwetting behavior have enormous application prospects. In particular, an air-water/oil amphibious superhydrophilic-superhydrophobic surface is advantageous in oil-water separation and oil-repellent materials. However, existing methods to create this property require either water pretreatment or time-consuming stimulation process, which makes instant oil-water identification impossible. Here, inspired by Namib desert beetle, we propose a strategy to construct layers differing in surface free energies to achieve surfaces that are simultaneously superhydrophilic-superoleophobic. Rough microcrystalline cellulose particles were modified by 2,2,6,6-tetramethyl-1-piperidinyloxy and perfluorooctanoic acid to successively construct high- and low-surface free energy layers. Surfaces prepared by simple spraying of these particles display excellent and stable superhydrophilicity-superoleophobicity under the amphibious conditions of air and water/oil, as well as excellent temperature and abrasion resistance. Pressed cotton membranes treated with these particles can effectively separate oil-water mixtures and oil-in-water emulsions without any pretreatment, even when the oil phase is highly viscous. Moreover, cotton gloves coated with these particles have superior water permeability and oil repellency without losing breathability. These results suggest a new approach towards oil-water separation and oil-repellent fabrics.