Beyond Surface Tension: Nonequilibrium Interfacial Mechanics of Pulmonary Surfactant Films
Pulmonary surfactants are often described in terms of their ability to lower surface tension, yet this description alone fails to explain lung mechanics under dynamic ventilation and pathological conditions. In this talk, I will show that pulmonary surfactant function is governed by nonequilibrium interfacial mechanics arising from microstructural reorganization under cyclic compression. Using a combination of interfacial rheometry and structural probes, we resolve how spontaneous or ventilator-induced sighs act as a mechanical reset that enriches the air-liquid interface with saturated lipids and drives the formation of mechanically robust, DPPC-rich films.
Experimentally, we combine methods to quantify shear, dilatational, and compressive responses under physiologically relevant deformations. These mechanical measurements are directly linked to interfacial structure using in situ neutron reflectometry and Raman-based spectroscopic mapping, allowing us to connect stress transmission to multilayer formation, compositional segregation, and compressional hardening. The results reveal that compressive stresses, rather than surface tension alone, play a central role in maintaining low interfacial stress and high lung compliance.
Beyond pulmonary surfactants, the framework and methods presented here are broadly applicable to soft interfacial materials, including polymer-laden interfaces, emulsions, foams, and bio-inspired films. The talk will conclude with an outlook on how mechanical conditioning and nonequilibrium processing can be leveraged as design principles for functional interfaces across areas of l engineering.
Bio: Jan Vermant studied chemical engineering at KU Leuven in Belgium, where he graduated in 1991. He received his doctorate in chemical engineering in 1996. Supported first by a postdoctoral fellowship from Elf Aquitaine and later by the Research Foundation Flanders, he conducted postdoctoral research at Stanford University, the CNRS in France and KU Leuven. In 2000, he joined the faculty of chemical engineering at KU Leuven, becoming a full professor in 2005. In 2014, he moved to the Department of Materials at ETH Zurich where he is professor of soft materials.