Wetting behavior of superhydrophobic surface in the liquid influenced by the existing of air layer

The oil-wetting behavior in water and water-wetting behavior in oil on superhydrophobic/superoleophilic surface and superhydrophobic/superoleophobic surface have been investigated. Two superhydrophobic surfaces both present an oil contact angle of about 0° in water, but show a water contact angle around 180° in oil. When two superhydrophobic surfaces are immersed in water, both of them retain a layer of air on the surface. The oil can crowd out the air and seep into the grooves on superhydrophobic/superoleophilic surface when oil droplet drips on the surface, but it will not occur on superhydrophobic/superoleophobic surface because of surface superoleophobicity. In oil, the rough grooves of superhydrophobic/superoleophilic surface fill with oil, but the superhydrophobic/superoleophobic surface keeps a layer of air on its grooves. The air layer makes the rough surface forming a continuous liquid/air interface in liquid. When the other liquid droplet drips on the surface, it will be a contact with liquid/air interface which accord with liquid spreading happening at liquid/air interface in air. And the situation and the shape of the other liquid droplet on the surface were also as same as it at liquid/air interface in air.