Substrate-Independent Wettability Patterning via Vapor-Based Polymer Nanocoating Deposition for Enhanced Droplet Transport

Wettability patterning plays a crucial role in regulating water droplet transport without external energy input. However, existing patterning technologies are often constrained by specific substrate materials or geometries. To address this limitation, this study introduces an approach that combines initiated chemical vapor deposition (iCVD) with photoactivated vapor grafting, enabling a solventless patterning process that is independent of the substrate material and surface geometry. This approach begins with the iCVD synthesis of a hydrophobic poly(allyl methacrylate) (PAMA) nanocoating that contains photoactive allyl groups, followed by selective grafting of a hydrophilic moiety onto ultraviolet-irradiated regions. Remarkably, this approach achieves patterning on substrates with diverse materials and geometries within 35 min, with resolutions reaching 10 μm. Because of the synergy between the cross-linking of PAMA and the grafting of 4-vinylpyridine, the wettability contrast exhibited excellent stability under harsh acidic, basic, and steam exposure conditions. The wettability contrast drives the coalescence of condensation droplets from the hydrophobic region into the hydrophilic region. The enhanced droplet transport, combined with the patterns’ geometric factors and the 3D substrate structure, significantly improves the efficiency of water collection and condensation heat transfer.