Wetting behavior of nanodroplets with low surface tension on pillar-type nanostructured substrates: Molecular dynamics simulations

Wettability played an essential role in surface science, and the wettability of low surface tension working fluids has a significant impact on the heat transfer and flow performance of micro and nanoscale equipment. Constructing surface structures was a significant method for adjusting wettability. Molecular dynamics simulations were conducted to investigate the wetting behaviors of different low-surface tension working fluids on the nano-pillar substrates with different spacings. A revised formula was adopted to determine the wetting state of droplets at the nanoscale. Contact angles at the nanoscale were predicted with the thermodynamic model. The effects of surface tension, droplet size, and the spacing aspect ratio on the wetting behavior of nanodroplets were studied comparatively. The results indicated that the revised formula was more accurate than the direct measurement method in determining the wetting state at the nanoscale. The thermodynamic model provided excellent predictions on contact angles in the Cassie and Composite states. However, the results had a massive decline in the Wenzel state, which was caused by the potential field distribution. This study proposed a revised parameter to determine the wetting state of droplets in nanoscale wetting, which was conducive to analyzing the nanoscale wetting state.