Anisotropic spreading on chemically heterogeneous surfaces: Insights from contact line approach

• Anisotropic spreading on chemically heterogeneous surfaces. • Validation of the contact line approach. • Droplet spreading varies with lyophilic pattern size and contact line coverage. • Uniform energy barriers maintain a circular contact area. • Varying energy barriers lead to a polygonal contact area. Studying the spreading of droplets on heterogeneous surfaces is significant for understanding various phenomena, from petroleum engineering to material science, due to its implications for wetting behavior, surface interactions, and functional coating applications. In this work, we investigated the spread of droplets on heterogeneous surfaces using molecular dynamics simulations. The results showed that the contact line approach can predict the equilibrium contact angle of droplet well. We found significant differences in the spreading of droplets on heterogeneous surfaces with different lyophilic pattern sizes, and then we explained the difference in droplet spreading on different heterogeneous surfaces by the proportion of lyophobic and lyophilic regions covered by contact lines. This study emphasizes the importance of contact lines in droplet spreading dynamics and enhances our understanding of the relationship between contact lines and droplet spreading.