A NEW METHOD FOR MEASURING CONTACT-ANGLE AND LIQUID SURFACE-TENSION APPLYING DETACHMENT OF 2-DIMENSIONAL MENISCUS

A method is proposed for measuring either the solid-liquid contact ang le or the liquid surface tension. The method applies the geometrical i nstability of a liquid meniscus, When a circular cylinder as a test so lid is horizontally immersed into a liquid bath and lifted up graduall y, a pair of two-dimensional meniscuses is formed under the side wall. At a certain critical height of the cylinder, the narrowest parts of the two meniscus curves contact each other, and the meniscus breaks do wn. Since the relation between the critical height H-Ber and the conta ct angle theta can be calculated theoretically, theta can be obtained by a simple measurement of H-Ber. It is possible to apply the same met hod for a plate used as a test solid. The liquid surface tension also can be measured by using a glass cylinder or plate to which most liqui ds attach at a = 0. The validity and usefulness of the method was expe rimentally confirmed for various solid and liquid samples. (C) 1998 Ac ademic Press.