LINE TENSION AND THE INTRINSIC CONTACT-ANGLE IN SOLID-LIQUID-FLUID SYSTEMS

An approximate theory for calculating the line tension in a solid-liqu id-fluid system is presented and demonstrated for a solid-liquid-vapor system. The line tension is shown to depend on the contact angle. Con sequently, the classical equation for the intrinsic contact angle, in terms of the line tension, is modified. The magnitude of the line tens ion is shown to be less than 5 x 10(-9) N, and its sign is shown to be positive for acute contact angles and negative for obtuse contact ang les. The deviation from the Young contact angle is shown to be negligi ble for drops of macroscopic size on an ideal solid surface. (C) 1997 Academic Press.