... in the divergent orifice. Resulting in favorable oil exudation. It is easier for oil droplet to depin by appropriately reducing the wall wetting angle, increasing the aperture or controlling the wall inclination angle. Ensure the self-healing and long-lasting lubrication film of porous oil-bearing surfaces...

...) p σ = 2 ⋅ σ r where p_σ is the capillary pressure, σ is the fluid surface tension, and r is the micro-channel radius. The size of micro-channel at interfaces is in micro/nano range and wetting effect cannot ignored under this condition...