Detecting nucleation of water in superhydrophobic PTFE powders using Inverse Gas Chromatography

Nucleation of water on superhydrophobic surfaces is critical to applications such as water harvesting, thermal management, and energy systems. Despite their hierarchical roughness and hydrophobic nature, such surfaces can contain nano-scale hydrophilic sites that promote strong adhesion and disrupt droplet departure mechanisms, reducing condensation efficiency. Identifying and characterizing these confined sites is challenging due to the resolution limitations and operational constraints of conventional techniques. This study employs novel characterization techniques, Inverse Gas Chromatography (IGC) and Dynamic Vapor Sorption (DVS), to detect and characterize critical properties of these hydrophilic sites. IGC quantifies surface energy components and intrinsic wettability, while DVS and IGC at controlled relative humidity identify the nucleation onset. Furthermore, IGC under humidity control demonstrates the capability to precisely pinpoint nucleation onset, circumventing DVS’s mass sensitivity limitations. Collectively, these advanced methods provide more comprehensive understanding of surface heterogeneity and offer new insights into optimizing super-hydrophobic surfaces for enhanced condensation performance. • Nano-confined hydrophilic sites detected on superhydrophobic PTFE. • Humidity-controlled IGC and DVS identify nucleation onset. • IGC precisely detects nucleation onset, overcoming DVS mass sensitivity. • IGC quantifies intrinsic wettability of nano-scale hydrophilic sites. • Pore size of nucleation sites estimated from IGC and Kelvin equation.