How Are the Wetting Properties of Silanated Surfaces Affected by Their Structure? An Atomic-Force Microscopy Study

We have studied silanated-silica surfaces concurrently by Atomic-Force Microscopy and contact angle measurements. Atomic-Force Microscopy observations evidenced two types of defects at the nanometer scale within the silane layers which were detected neither by contact angle nor by contact angle hysteresis measurements. In contrast, in the case of incomplete silane layers, these latter measurements exhibited a high sensitivity to the surface coverage as soon as it becomes lower than a critical value. Chemical modifications of the tip have been performed and measurements of the adhesion forces are reported.