The Interfacial Structure of Water on a Hydrophobic Surface - A Mechanistic Study Yingxi Elaine Zhu, Dept. of Chemical & Biomolecular Eng., Univ. of Notre Dame, Notre Dame, IN This research aims to understand the interfacial molecular structure and water transport at near the surfaces of varied hydrophobicity by complementary force-sensing and microscopic approaches. To explore the interfacial structure at the water-surface interface, we study the morphology of polymer stain from evaporating a polymer aqueous droplet at surfaces of varied hydrophobicity. The contact line in an evaporating drop can stay pinned to form a single ring or can shrink in a discontinuous step-wise manner and generate multiple rings. In addition, the composition of the binary system can significantly disrupt the periodic multiple-ring patterns, which could result in the rippled rings and curtain-like periodic patterns with a curious spoke-like structure as the size of colloidal particles increases. In addition, the water wettability can be effectively tuned by applied AC-electric fields at varied AC-frequency and amplitude. (a) Evaporation Dewetting Stagnation flow Film rupture (i) 88.3 s 105.6 s (ii) 108.8 s (iv) ( iv)