Geometry-Driven Robust Superhydrophobicity on Hydrophilic Materials by Hybrid Salvinia-Inspired Structures

Superhydrophobic surfaces (SHSs) provide multifunctional benefits, including self-cleaning and antifouling. However, maintaining robust performance on intrinsically hydrophilic substrates without chemical coating remains a major challenge. On such materials, even minor mechanical wear can damage micro- and nanostructures, triggering premature wetting transitions and rapidly degrading superhydrophobic behavior. In this study, two-photon polymerization (TPP) is used to fabricate Salvinia-inspired and Salvinia-derived architectures—including conventional, staggered, self-similar, and hybrid designs—on intrinsically hydrophilic substrates. This fabrication platform enables a systematic investigation of how purely geometric features govern the retention or loss of wetting-state stability under progressive, spatially uniform wear, with surface chemistry held constant. Using controlled geometric degradation (fabrication-based wear simulation) and wettability characterization, including static and dynamic contact angles, evaporation-induced transitions, and droplet impact tests, this work demonstrates that hybrid designs combining vertical redundancy with lateral misalignment significantly delay wetting transitions and sustain superhydrophobicity under extended abrasion. These findings establish geometry-driven design principles that enhance the mechanical robustness of SHSs on hydrophilic substrates, offering a promising pathway toward durable, chemistry-free functional surfaces.