Influence of Bulk Viscosity on the Interfacial Properties of Highly Viscous Extended Liquid Thin Films

Extended thin films have been extensively studied in the context of interfacial and microscale fluid transport, yet the behavior of polymeric fluids at this scale has remained largely unexplored. This gap is addressed in this study, which investigates the interfacial characteristics of polymeric fluids, with a particular focus on how rheological properties, such as viscosity and power-law behavior, influence thin film dynamics. Experimental investigations are conducted using image analysis interferometry, through which the extended liquid film thickness, slope, and curvature are observed, providing key insights into interfacial behavior. Hamaker constant is determined using established techniques, allowing for the quantification of van der Waals interactions. A numerical model is developed to understand the dynamics of extended thin films. The model integrates the augmented Young-Laplace equation and serves as a foundation for more advanced theoretical models. Experimental data are used to validate the theoretical predictions, revealing that viscosity plays a significant role in governing extended liquid thin film behavior, particularly in spreading dynamics, and interfacial properties. Through the combination of experimental and theoretical approaches, the understanding of polymeric extended thin films is enhanced, providing a foundation for applications in areas such as point-of-care diagnostics, microfluidics, and heat transfer technologies.