Interfacial thermal resistance and contact angle dynamics of evaporating water droplets under Leidenfrost conditions

• MD simulations reveal the nanoscale onset and evolution of the Leidenfrost effect. • Real-time contact angle and heat transfer tracked during droplet evaporation. • Interfacial thermal resistance captures onset and growth of Leidenfrost transition. • Surface roughness modulates wetting and delays the Leidenfrost temperature rise. This study presents the first molecular dynamics (MD) simulations to characterize interfacial thermal resistance (ITR) during nano water droplet evaporation under Leidenfrost conditions on nanopatterned silica surfaces. By systematically varying nanoscale surface roughness, we examined how geometry influences droplet dynamics, contact angle evolution, and interfacial heat transfer. As evaporation progressed, the contact angle increased by up to 30° during the pinning–depinning dynamics of the shrinking droplet prior to complete evaporation. ITR was computed by tracking the temperature discontinuity across the solid–liquid interface and the associated heat flux. Prior to the Leidenfrost transition, ITR remained nearly constant, emerging as a distinct material property of the solid–liquid pair, despite increasing temperature gradients. As the system reached the Leidenfrost point, the ITR gradually increased by up to three orders of magnitude, presenting the reduction in thermal coupling. Increased surface roughness reduced the initial contact angle and better accommodated its temporal evolution during evaporation, which delayed the onset of the Leidenfrost effect, raising the Leidenfrost temperature by up to 59 K (∼11.5 %). These findings offer novel molecular-scale insights into phase-change heat transfer and interfacial thermal resistance, with implications for high-performance thermal management, materials processing, and the design of thermal protection systems for extreme environments.