Interfacial Phenomena of Natural Pulmonary Surfactants at the Perfluorocarbon-Water Interface

Breathing depends on a thin natural material that coats the inside of the lungs and helps keep the tiny air sacs open during each breath. Scientists understand how this material functions under normal conditions. However, much less is known about its behavior when the lungs are filled with oxygen-carrying liquids rather than air. Liquid-based breathing approaches have shown promise for treating severe respiratory failure. They may find applications in emergency medicine, deep-sea operations, and space exploration. However, the scientific challenges associated with these systems have limited their development. This project addresses a fundamental engineering question: how do molecules and microscopic particles organize themselves and function at the boundary between two liquids? These liquid-liquid interfaces play important roles in biological systems, advanced manufacturing, biotechnology, and energy technologies. The project will develop new experimental tools to enable scientists and engineers to study these interfaces with unprecedented precision. The project will also support the education and training of undergraduate, graduate, and postdoctoral researchers. Outreach activities will engage K–12 students and teachers through hands-on learning experiences that introduce concepts in engineering, and materials science. The project will investigate the interfacial behavior of natural pulmonary surfactant films at the interface between water and medically relevant perfluorocarbon liquids used in liquid ventilation. A primary objective is to develop a miniaturized droplet-based experimental platform that enables quantitative characterization of both spread and adsorbed surfactant films at liquid-liquid interfaces. The approach extends constrained drop surfactometry, previously developed for air-water surfaces, to systems involving two immiscible liquids. Using this platform, the project will examine three fundamental aspects of surfactant behavior: (1) thermodynamic phase behavior and structural organization of surfactant films, (2) dynamic interfacial activity of surfactant under physiologically relevant conditions, and (3) mechanisms by which proteins, lipids, and viral components inhibit surfactant function. Measurements of interfacial tension, film compressibility, and interfacial rheological properties will be integrated with high-resolution imaging of transferred interfacial films. The resulting platform will provide a general methodology for investigating molecular and colloidal self-assembly at liquid-liquid interfaces that are difficult to study using existing experimental approaches. The project is expected to advance fundamental interfacial engineering science, establish new tools for studying complex liquid interfaces, and provide mechanistic insight into the role of pulmonary surfactants in liquid ventilation technologies. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.