Sessile-drop contact angle measurements using axisymmetric drop shape analysis

Abstract

Sessile-drop contact angle measurements have been performed using a new technique which fits the Laplace equation of capillarity to an arbitrary array of coordinate points selected from the drop profile. The approach is unique as it does not depend on the location of specific features of the drop shape and is generally applicable to all axisymmetric liquid-fluid interfaces; i.e., sessile or pendant drops and contact angles both greater than or less than 90°. Previous publicatons have described the numerical algorithm and its use in the determination of surface and interfacial tensions. As a means of evaluating sessile-drop contact angles, the accuracy and precision of the technique are unequalled, and its relative simplicity and freedom from operator subjectivity combine to make it an attractive alternative to the more traditional approaches.