Competitive adsorption–induced non-thermal pseudo-Leidenfrost effect in supercritical CO₂ enabling nanoscale dewetting

Controlling droplet adhesion and interfacial dewetting on solid surfaces is important for droplet manipulation and liquid removal in a wide range of applications, particularly in the wet cleaning of micro/nanostructured semiconductor chips, where trapped water residues can compromise structural stability. Therefore, a strategy that reduces droplet adhesion without relying on surface structural modification is highly desired. In this work, a novel supercritical CO₂-mediated droplet levitation mechanism, termed the pseudo-Leidenfrost effect, is proposed based on the conventional thermally driven Leidenfrost effect. Compared with its thermally driven counterpart, the proposed scCO₂-mediated mechanism avoids the need for global substrate superheating while forming a denser and more stable CO₂-rich interfacial cushion beneath the droplet. Molecular dynamics simulations indicate that this mechanism is primarily driven by the competitive adsorption between CO₂ and H₂O on the surface, which leads to the formation of a molecular cushion beneath the nanodroplet and thereby enables droplet levitation. Density functional theory calculations further indicate that the adsorption affinity of CO₂ on the surface must be comparable to or greater than that of H₂O to ensure the stable emergence of the pseudo-Leidenfrost effect. This work provides a novel non-thermal strategy for droplet manipulation, along with atomistic and nanoscale insights into the underlying mechanism.