The pinning characteristics of droplets and the self-repair mechanism of lubricating film on nanoporous surface: A molecular dynamics perspective

The nanoscale pore gives rich dynamic information to the flow behavior of the droplets exuded on the SLIPS (Smooth Liquid-Infused Porous Surface). The key to realizing fast self-healing of lubricating film is to understand the dynamic law of droplets at nano-orifice. In this paper, a dynamics model of the exudation and spreading behavior is established by the non-equilibrium molecular dynamics simulation. The characteristics and the mechanism of pinning and spreading of nano-droplets were studied. We found that adjusting the wettability and pore diameter can change the liquid exudation and the pinning time of droplets at the orifice. The weaker wettability and larger pore diameter both can increase the exudation velocity and reduce the pinning time of the droplets, which then improves the spreading of exuded droplets and the self-repairing efficiency of the damaged liquid film. As the pore diameter increases, the spreading area of the droplets on the surface of the pore increases. The increase in the wettability also facilitates the spreading behavior, but the outflow rate of the liquid from the pore decreases. Under the combined effect of the two factors, the spreading area of droplets first increases and then decreases with the wettability increases. The results provide potential insights into the spreading mechanism of nanodroplets on porous surfaces.