| Interfaces are inherent whenever two dissimilar phases contact one another. As such, interfaces are found virtually everywhere and are of great significance. Understanding how to control and manipulate interfacial properties at the molecular level is beneficial as they can have profound effects on bulk phase macroscopic behavior. In this thesis, the effects of particles on the deformation and flow of fluid/fluid interfaces and how this relates to macroscopic behavior are examined.; The first system studied is an industrially important example where interfacial properties greatly influence bulk properties, namely an emulsion. Inhibiting the tendency of emulsions to phase separate can be accomplished through the addition of amphiphiles that collect at the interface, modifying transport processes involved in coalescence and film drainage. Since drainage and merging phenomena are influenced by the mechanics of the drop interfaces, measuring interfacial rheology can offer insight into stability mechanisms. In particular, adding particulates that collect at interfaces to form viscoelastic films can effectively diminish coalescence. In this way, particles at interfaces are beneficial.; However, the presence of particles at interfaces is not always favorable, as is true for the inhalation of airborne pollution particles. Oxygen uptake and carbon dioxide release take place in the terminal air sacs of the lungs, called alveoli. The alveolar walls are comprised of epithelial cells, which are coated with an aqueous liquid layer. The interface between this liquid layer and the air inside consists of a complex mixture of phospholipids, lipids, and surfactant-specific proteins, known as the pulmonary surfactant system. Pulmonary surfactant films dramatically lower interfacial tensions while remaining extremely fluid (a characteristic impossible for a single component film). This property is crucial as it decreases work requirements for breathing, facilitates oxygen uptake, and prevents alveolar collapse during the respiratory cycle. Air pollution particles can deeply penetrate the lungs and deposit in the alveoli. After deposition, particles interact with the surfactant film and the underlying epithelial cells, causing severe surfactant and cellular damage. Consequently, the pulmonary surfactant film becomes highly viscoelastic and breathing efficiency is greatly reduced. In this way, the presence of particles at an interface is detrimental. |
