Automation of axisymmetric drop shape analysis for measurements of interfacial tensions and contact angles

Abstract

Axisymmetric drop shape analysis-profile (ADSA-P) was developed to determine liquid-fluid interfacial tensions and contact angles by fitting the Laplace equation of capillarity to an arbitrary array of coordinate points selected from the drop profile. The data acquisition method, which consisted of the manual measurement of a number of coordinate points of a photographic image of a drop, was found to be time consuming and inaccurate. An automatic digitization technique utilizing recent developments in digital image acquisition and analysis to achieve rapid and accurate data acquisition and preprocessing is presented. The technique eliminates errors due to the optical distortions. It was found that high accuracy could be obtained through the use of sub-pixel resolution in determining the drop profile coordinates. The results obtained not only compared well with the conventional methods, but also considerably outstripped the accuracy of conventional methods.