MEAM Seminar: “The Secret Life of Interfaces: Solute-Rich Films, Slippery Ice, and Continuous Emulsions”

Phase change concentrates the action into a narrow region near the moving interface, where composition, transport, and interfacial disorder evolve rapidly and determine macroscopic outcomes. In this talk, I will show how controlling that transient interfacial environment shapes two disparate problems: how ice adheres to solids and how emulsions form and persist. I will begin with ice adhesion in realistic, impure water. Our experiments show that trace impurities can reduce ice adhesion on hydrophilic surfaces by orders of magnitude, reaching the sub-kPa regime. Freezing-driven solute rejection and local enrichment are part of the story, but not the whole story. The ice–solid boundary develops a dynamic interfacial structure that depends on how and where liquid is retained, how disorder is organized at nanometric scales, and how these features evolve as the freezing front advances. Using advanced interferometry, we directly track the formation and evolution of the interphase in situ and connect it to measured adhesion outcomes. I will discuss when a lubricating interphase persists, when it collapses under stronger driving forces such as deeper subcooling, and how these competing regimes translate into practical rules for ice repellency and freeze protection. In the second part of the talk, I will use the same focus on interfacial enrichment and kinetics to build, rather than release, soft materials. I will present an energy-efficient route to emulsification based on vapor condensation onto a subcooled, surfactant-laden liquid. In this process, droplet nucleation, submersion, and growth occur at the liquid interface, while stabilization is set by adsorption kinetics and transport. This enables shear-free production of submicron emulsions with low polydispersity, and it naturally extends to continuous thin-film operation where residence time and replenishment address depletion limits and allow dense formulations with high dispersed-phase fractions. I will close by highlighting a common theme: phase change creates a transient interfacial microenvironment and engineering that microenvironment controls whether the interface releases cleanly or self-assembles reliably.