Wetting State Transition of Liquid Gallium Drop At Nanoscale

Wetting state transition regulated by surface roughness has increasing importance for its wide application. Molecular dynamics simulations have been performed to study the wetting state transition induced by the surface roughness in the gallium-carbon system. There is a transition from the Wenzel state to the Cassie state when the roughness is changed. When the surface roughness is more than 1.8, gallium droplet is in Cassie state, but less than 1.6, it is in Wenzel state. The substrate composed by irregular pillars has the similar effect on the wetting state transition. Besides, the distinctive variations occur in the interface tension, the mean-squared displacement, the wetted surface and the interaction energy as the wetting state changes, which is further explained by a proposed model. This study would provide significant guidance for designing the superhydrophobic surfaces in the future.