Simultaneous measurements of thin film thickness using total internal reflection fluorescence microscopy and disjoining pressure using Scheludko cell.

This work describes a method for measuring the thin film thickness using total internal reflection fluorescence microscopy, with the use of evanescent wave illumination. The thin liquid film was formed in a hole drilled at the center of a porous plate, which is used for measurement of the disjoining pressure by using the Scheludko cell method. The aim of simultaneous and in situ measurements of thin film thickness and disjoining pressure is to obtain the relationship between them, which is critical for explicitly depicting the thin film profile that determines the interfacial mass and heat fluxes in the thin film region near the triple line. This method can overcome the drawbacks of the optical methods that are insufficient for measuring the thickness of a thin film with curvature. The influence of structural forces formed by tracer nanoparticles seeded in the thin liquid film on the relationship was analyzed. The obtained expression for disjoining pressure vs thin film thickness provides a basis for analyzing the formation, evolution, and stability of the thin liquid film, which is the dominant mechanism of controlling the mesoscopic structure in many transport processes.