Wettability of complex Long-Chain alkanes droplets on Pillar-type surfaces

Abstract

To reveal the difference in wettability of long-chain alkane and simple molecular materials on the structural surfaces, we employ long-time molecular dynamics simulation to study the wettability of complex alkane droplets on flat and pillar-type surfaces by comparing the contact angle and the transition of the wetting state. The results showed that the transition of the wetting state depended on the joint action of potential coefficient, pillar spacing, and pillar height, and the wetting state of droplets could transform into each other among Wenzel state, Cross state, and Cassie state. The accurate ranges of the predicted values of the Cassie formula were the weaker fluid–solid attraction and smaller pillar spacing. In contrast, the accurate ranges of the predicted values of the Wenzel formula were the stronger fluid–solid attraction and smaller roughness. When the fluid–solid attraction was strong and the pillar spacing was small, both the Wenzel and Cassie formula could accurately predict the corresponding contact angle. By giving the corresponding conditions of the Cross state and revealing the differences in alkane droplets with variable chain lengths in the transition of the wetting state, it could serve as a reliable reference for subsequent simulations of complex materials on nanostructure surfaces.