ABSTRACT
The surfaces of most practical materials are heterogeneous (different functional groups, chemical non-uniformity, contaminations, mixtures of different solids, etc) and they are not ideally smooth. Therefore, a material may have different contact angles at local microspots. The averaging of contact angles on the micro spots results in an “effective contact angle” for the material. The wetting force, capillary pressure, capillary rise, wicking rate, liquid partitioning between layers, wetting-rewetting, etc. are proportional to cosine of the effective contact angle, 0.
