Underwater superoleophobicity of the femtosecond laser-structured PDMS surface after oxygen plasma irradiation. (a, b) SEM images of the ablated PDMS surface. (c) Water droplet (in air) and (d) oil droplet (in water) on the rough PDMS surface before plasma treatment. (e) Water droplet (in air) and (f) oil droplet (in water) on the rough PDMS surface after plasma treatment. (g) Oil droplet rolling on the tilted underwater superoleophobic PDMS sample in water. (h) Oxygen plasma-induced chemical change of the PDMS surface. Reproduced from [89
] with the permission.