Atmosphere-Mediated Scalable and Durable Biphilicity on Rationally Designed Structured Surfaces

Biphilic surfaces having spatially distinct wetting have the potential to enable a plethora of applications ranging from fog harvesting, microfluidics, advanced manufacturing, and pumpless fluid transfer. However, complex and costly fabrication along with poor durability have hindered the widespread utilization of biphilic surfaces. Here, hierarchical biphilic micro/nanostructured surfaces passively functionalized by the atmosphere are demonstrated as a platform to create scalable and abrasion-resistant biphilic interfaces. Biphilic hierarchical copper oxide (CuO) nanowires are fabricated on copper substrates via laser ablation followed by thermal oxidation. The surfaces spontaneously become globally superhydrophobic and locally hydrophilic due to the adsorption of airborne volatile organic compounds on the ultrahigh surface energy CuO nanowires. The curvature-dependent spatial variation in nanowire morphology enables local roughness variation and wetting contrast without the need for selective functionalization. Coalescence-induced droplet jumping and water vapor condensation experiments demonstrate global superhydrophobicity with discrete local hydrophilicity. In addition to enhanced fog harvesting rates, the surfaces are demonstrated to have repeatable self-healing function with enhanced abrasion resistance compared to single-tier structured surfaces. The work not only develops a facile method of fabricating scalable biphilic surfaces via nanoscale structure variation and atmosphere-mediated surface modification, but also provides insights into the role of wetting contrast on droplet dynamics.