A method and apparatus for determining the contact angle and/or surface tension of a liquid on a solid surface is described. The method involves placing a fluid drop on a solid surface, and gradually increasing its volume by adding more fluid, while continuing to determine the corresponding increase in fluid height, until the drop attains maximum height beyond which additional fluid only increases the drop footprint and not height, and determining the equilibrium height and in turn the contact angle by means of an equation that correlates contact angle with depth below the fluid surface, together with the fluid surface tension and liquid density. The method may in turn be used to determine the fluid surface tension from the equilibrium height when the contact angle and density of the fluid are known.
University of Northern Iowa Research Foundation
Behroozi, Feredoon, "Method and apparatus for measurement of fluid properties" (2013). Patents (University of Northern Iowa). 5.