ABSTRACT
Numerous methodologies have been developed for the measurement of interfacial properties including contact angles and surface tensions. Contact angles are most commonly measured by aligning a tangent with the profile of a sessile drop at the point of contact with the solid surface. Liquid surface tension measurements commonly involve the determination of the height of a meniscus in a capillary or on a fiber or a plate. Some of the major methods including the Wilhelmy plate technique and Du Nouy ring method [1-5], the drop weight method [2-5], the oscillating jet method [3,4], the capillary wave method [3,4], and the spinning drop method [2-5] are briefly reviewed in this section. An overview of these techniques reveals that, in most instances, a balance must be struck between the simplicity, the accuracy, and the flexibility of the methodology. Alternative approaches to obtain the interfacial properties are drop shape methods developed to determine the liquid-vapor or liquid-liquid interfacial tensions and the contact angle from the shape of a sessile drop, pendant drop, or captive bubble. These methods are widely used due to their simplicity and accuracy. In this section, the drop shape methods are described in detail.
