CONTACT-ANGLE HYSTERESIS ON HETEROGENEOUS SMOOTH SURFACES

An oscillatory dependence of the highest and lowest possible contact angles on the volume of a drop is demonstrated for a simple model of a two-dimensional (cylindrical) drop placed on a periodically heterogeneous but smooth solid surface. This type of dependence may explain the macroscopic jumps observed during measurements of contact angle hysteresis. In addition, the present calculations reveal a possibility of dependence of the advancing and receding contact angles on the drop volume, in qualitative agreement with available experimental data. The effect of asymmetry in placing the drop relative to the surface heterogeneity pattern is also discussed and found to be an important factor in the interpretation of contact angle hysteresis. (C) 1994 Academic Press, Inc.