ABSTRACT
The characterization of solid-liquid interactions is important for understanding surface properties, such as adhesional strength. For equilibrium studies, the contact angle produced by various fluids on a solid has been a traditional method of quantifying the type of surface. More recently, measurement of the dynamic contact angle has been important for understanding the approach to equilibrium and film formation properties. The most direct methods of contact angle measurement involve direct visual observation of a liquid droplet using either a profile or a plan view [1]. The side profile allows a simple cross-section to be obtained and is particularly convenient for digital image analysis. However, the spatial resolution can be limited and a cross-section may not be typical of the whole droplet if the surface is heterogeneous. The plan view can involve interferometry and provides
a view of the whole periphery of a droplet whilst retaining the potential for digital image analysis. These direct methods can also be combined with video analysis to enable dynamic information to be extracted [2]. If we want to look at microscopic films, rather than macroscopic profiles, then laser interferometry [3], ellipsometry [4], and X-ray reflectivity [5] are all possible methods.
