Title: Engineering multiphase soft materials for sustainability

Abstract

The stability and rheology of multiphase materials, such as foams and emulsions, are controlled by interfacial properties and by the thin liquid films (TLFs) that form between neighboring droplets or bubbles. When two bubbles approach each other, a TLF is created and thins over time due to drainage, ultimately determining whether the bubbles coalesce or remain stable. Despite their nanometric thickness, these films play a central role in setting the macroscopic behavior and lifetime of many soft materials.

In this talk, I will discuss how interfacial stresses, capillarity, hydrodynamics, and intermolecular interactions mediated by surface-active species control TLF thinning and stability. Experimental techniques such as the dynamic thin film balance and interfacial shear rheometry allow us to directly probe the nano- and micro-scale physics underlying these processes and to connect interfacial dynamics with bulk rheological behavior and macroscopic stability.

I will then highlight how these insights can be used to design sustainable multiphase materials with applications relevant to the EU, Crete and the broader Mediterranean region. Examples include biodegradable firefighting foams for increasing wildfire risk, plant-based edible foams and emulsions for sustainable food systems, and foams and emulsions operating in saline environments for marine and seawater-related applications, including those used in emerging pollutant separation processes.

Figure 1: (Left) Microinterferometry image of a foam film stabilized by a protein (yellow-pea albumin). (Right) Correlating foam half-life with film thickness.

[1]           Chatzigiannakis, E., & Vermant, J. (2024). Journal of Rheology, 68(4), 655-663.

[2]           Chatzigiannakis, E., Yang, J., Sagis, L. M., & Nikiforidis, C. V. (2025). Journal of Colloid and Interface Science, 683, 408-419.