Wettability-dependent curvature effects on explosive boiling of nanofilms: Direct and oscillatory-instability-mediated pathways

Explosive boiling of nanofilms is jointly governed by surface wettability and geometry, yet whether wettability alters the mechanism through which continuous curvature regulates phase change remains unclear. Molecular dynamics simulations were performed for a 6-nm Ar film on planar and continuously curved Au substrates at 290 K, covering four contact angles (43°, 87°, 100°, and 127.1°) and four curvatures ( H =0, 0.03, 0.04, and 0.05 nm −1 ). Two distinct boiling pathways were identified. On hydrophilic surfaces, local interfacial separation developed directly into persistent vapor-gap growth and complete nanofilm separation from the substrate. On hydrophobic surfaces, the vapor gap repeatedly expanded and contracted, accompanied by local separation and recontact, before stable boiling was established, forming an oscillatory-interfacial-instability-mediated pathway. Curvature generally shortened the boiling-onset time under hydrophilic conditions but produced a nonmonotonic response under hydrophobic conditions by regulating the duration of the precursor instability. Layer-resolved temperatures showed that curvature reduced the through-thickness temperature gradient, whereas increasing hydrophobicity raised the interfacial thermal resistance and intensified its fluctuations. These results demonstrate that wettability determines the fundamental boiling pathway, while curvature regulates either the timescale of direct boiling or the evolution of precursor interfacial instability. The findings provide an atomistic basis for jointly tailoring wettability and continuous curvature in nanoscale phase-change thermal management.