A slippery hydrogel coating with durable oil-repellent property and self-regeneration capacity

Traditional lubricant impregnated surfaces usually required fluorinated lubricants to achieve slippery oil repellency, but the lubricants infused were expensive and toxic and also suffered from limited stability because of their migrating, evaporating, and leaking during use. Herein, to address this issue, we fabricated a durably fluorine-free slippery oil-repellent hydrogel coating using water as the lubricant. Due to its enhanced water-binding affinity, water could wet the hydrogel completely and form a hydrated-water layer on the surface The hydrated water layer could act as a lubricant to repel foreign oils, which allowed the hydrogel to display slippery oil-repellency in air, exhibit superoleophobicity underwater, and resist oil fouling upon oil immersion. The hydrogel kept its oil-repellent properties after mechanical tests as well as thermal and freezing treatments, demonstrating its durability. Thanks to its moisture absorption, the water lubricant layer could self-regenerate upon the lubricated water layer depletion through exposure to a humid environment. Exploiting it is water-attracting and oil repellency, the hydrogel coating was demonstrated as a versatile platform for oil/water separation, polymer/water separation, drag-reduction, and anti-fogging.