Molecular dynamics simulation on wetting characteristics and dynamic wetting behavior of a nanodroplet on a liquid-like soft surface

Soft wetting played an important role in microfluidics, anti-icing, coating technology, and many application fields. The soft wetting behavior of nanodroplets on the soft material interface was investigated with molecular dynamics simulation. The liquid-like silicone oil was selected as a typical soft surface material, and the contact angle and the wetting ridge of droplets in the static wetting phenomenon were analyzed. The motion mechanism of droplets on soft surfaces during dynamic wetting process was elucidated, and the changes of wetting ridges during droplet motion were revealed. Effects of external forces, temperature, and surface tension on the dynamic behavior of soft wetting were discussed. The results indicated that the wetting ridge height in static soft wetting phenomenon decreased with the decrease of the droplet surface tension, and the corresponding apparent contact angle also decreased monotonically. The co-existed sliding-rolling motion was discovered when droplets moved forward under the horizontal external force. The variation of sliding and rolling velocities showed opposite tendency, and the proportion of sliding velocity in the entire velocity increased with the increase of horizontal force. The droplet velocity had a nonlinear relationship with the external force. This study was helpful to gain a deeper understanding of the dynamic behavior in nano-soft wetting phenomena, providing theoretical guidance and reference for designing nano-soft devices.