Enhancing liquid-vapor phase behavior through multiscale anisotropic wettability gradient in dandelion-inspired nanostructures.

Effective manipulation of liquid-vapor phase behavior is essential for advancing energy efficiency. This study presents a synthetic strategy for creating multiscale anisotropic wettability gradients through the assembly of dandelion-inspired nanostructures, achieving both horizontal (planar) and vertical biphilicity. This versatile approach is applicable to various nanowire materials, including silicon, zinc oxide, and copper oxide. Key findings demonstrate that these surfaces can be tuned to transit from jumping-droplet to dropwise and filmwise condensation while maintaining a stable Cassie state for the condensate. This configuration allows water droplets and films to float on the nanowire substrate, with dry nanowires beneath the water acting as vapor channels that promote droplet nucleation. Unlike traditional liquid film condensation, the ultrathin water film, measuring less than 2 μm in thickness, floats on the nanostructured surface, significantly reducing thermal resistance and enabling rapid condensate removal. The complex biphilic surfaces with a micro-nano-nano hierarchy effectively direct and organize water nucleation, facilitating controlled water flow and droplet departure from the surface. These findings underscore the potential of this innovative design to optimize liquid-vapor phase behaviors, offering transformative implications for enhanced heat transfer and fluid management in various applications.