3D Confocal Scanning Laser Microscopy to Quantify Contact Angles in Natural Oil-Water Mixtures

3D Confocal Scanning Laser Microscopy to Quantify Contact Angles in Natural Oil-Water Mixtures — The contact angle of a liquid drop on a solid surface is one of the most simple, useful and sensitive parameters in the hydraulic sciences to quantify and to qualify the wettability and the surface energy of different materials. In this paper, a confocal scanning laser microscope (CSLM) has been used to quantify contact angle and then the wettability. This technique uses a laser scan and allows series of 2-D images of a fluorescent liquid droplet set on various solid surfaces to be recorded. The generation of 3-D images is carried out with the summation of several images acquired with a regular step along the CSLM z-axis. The results obtained are compared and discussed with those obtained with a conventional goniometric technique for different solid-liquid-air systems. CSLM results show that similar values are obtained with both methods. Thus, this technique shows that the length interval of sampling between the solid contact and the curvature rupture of the drop seems to be essential to correctly estimate the contact angles. This method allows the study of the local contact angle along the periphery of the drop, and the deformation of the drop shape. Construction of 3-D images shows that drops are characterized by complex morphologies and that the local contact angles can be modified by chemical heterogeneities in the fluids. Oil & Gas Science and Technology – Rev. IFP, Vol. 63 (2008), No. 5