Low-Temperature Leidenfrost Foams: A Fluid-Structure Approach to Droplet Levitation

The Leidenfrost effect, in which a liquid levitates on its own vapor film above a heated surface, has long fascinated researchers in fluid dynamics and interfacial thermophysics. Despite extensive study of single-phase droplets, the phenomenon remains constrained by two key limitations: it typically occurs at temperatures far above the liquid’s boiling point, and lowering the transition temperature generally requires specially engineered or coated surfaces to stabilize the vapor layer. These constraints limit both fundamental understanding and practical application, leaving a fundamental question unresolved: to what extent can the Leidenfrost point be reduced to enable stable droplet levitation at low temperatures without surface modification?Our preliminary experiments have revealed an unconventional phenomenon: liquid foams, composed of gas bubbles dispersed within a continuous liquid phase, can sustain stable Leidenfrost-like levitation at 110°C on unmodified surfaces—close to the boiling point of water and significantly below the ~130°C threshold reported in previous studies employing surface modifications. This striking discovery underscores the crucial roles of bubble dynamics, vapor generation, and interfacial thermofluidics in governing foam–surface interactions. Distinct from conventional single-phase liquid behavior, this finding points to a fundamentally new, fluid-structure-based mechanism for selfsustained levitation at record-low temperatures, representing a paradigm shift from surface engineering to fluid engineering.This project aims to elucidate the physical principles underlying low-temperature Leidenfrost foam levitation and to explore its potential for functional applications. Four interconnected research tasks are proposed. First, liquid foams with precisely controlled bubble size, gas volume fraction, and composition will be generated using microfluidic technique to provide a reproducible experimental platform. Second, systematic studies will quantify how foam and substrate properties affect vapor-film formation and stability, leading to a comprehensive phase map of low-temperature Leidenfrost behavior. Third, predictive models coupling bubble deformation, vapor-layer evolution, and heat transfer will be developed to capture the onset and persistence of foam levitation. Finally, proof-of-concept demonstrations will showcase the use of Leidenfrost foams for effective thermal shielding and contactless cargo transport on heated surfaces.The proposed study will yield a theoretical framework for low-temperature Leidenfrost behavior in multiphase fluids, revealing how foam morphology governs vapor-film dynamics and low-temperature levitation. By uncovering how vapor layers can form and persist at near-boiling temperatures on plain surfaces, the study will lay the scientific foundation for innovative technologies, including effective thermal management and contact-free transport systems, with broad relevance to advanced manufacturing, electronics, and aerospace applications.