Drying-Induced Hierarchical Dimple Patterns on Partially Miscible Polymeric Films Under Ordered Convections

Abstract

We describe the formation of hierarchical dual dimple patterns on polymeric sublayers by evaporation-induced interfacial stress. As water vapor condenses on partially miscible volatile sublayers, the resulting unstable wet-on-wet configurations trigger droplet assembly under ordered convection, giving rise to hexagonal traces of surface dimples, which coexist with highly ordered dimple arrays. Monitoring the time-dependent Marangoni numbers proved that the interfacial stress plays a crucial role in the transition between hierarchically and uniformly ordered dimple patterns.

Keywords:

• Coating
• Dimple
• Drying
• Films
• Marangoni convection
• Microstructure

ACKNOWLEDGMENT

The authors acknowledge financial support from the Japan Society for the Promotion of Science (JSPS) KAKENHI (23560912) Grant-in-Aid for Scientific Research C.