Droplet Wetting Synergy on Hydrophobic/Hydrophilic Dual-Phase Substrates

Abstract This study fabricated alternating hydrophobic–hydrophilic micropatterned surfaces using photolithography, chemical vapor deposition, and reactive ion etching. Hydrophilic regions were flat SiO₂, while hydrophobic square patterns (10 and 40 µm) were prepared via (i) perfluorinated low-surface-energy self-assembled monolayers (SiO₂-FT-SAM), (ii) RIE-induced roughening (SiO₂/SiO₂*), and (iii) combined roughness and SAM modification (SiO₂/SiO₂*-FT-SAM). Wettability was evaluated at hydrophobic area fractions of 25%, 50%, and 75%. At 40 µm feature size and 75% coverage, the hybrid surface achieved a static contact angle of 138°, indicating a stable Cassie state with a trapped air layer. The observed reversibility of the air film further supports the synergistic roles of micro-roughness and low surface energy. Overall, this approach enables effective wettability control and supports the development of self-cleaning, low-adhesion surfaces.