DIRECT MEASUREMENT OF THE CONTACT-ANGLE ON PLATES AND ON THIN FIBERS - SOME THEORETICAL ASPECTS

The experimental problem of making accurate measurement of the contact angle by direct measurement in systems where the substrate is in the form of either a plane or a thin cylinder is discussed theoretically. The importance of such measurements of the liquid meniscus curvature close to the solid surface is discussed in a quantitative way. It is shown that, by arranging for one of the contacting phases to be in either the droplet or the bulk form, it is possible, in principle, to make direct measurements in all the systems considered. With cylinders, the facility of the experiment increases with an increase in the cylinder diameter.