A measurement technique has been developed to measure the contact angle with of a confocal device. This technique has the unique advantage of allowing to perform both topography and contact angle measurements in the same location, therefore avoiding any shift in the sample positioning between the two measurements and ensuring the proper location of both measurements in the same area of the sample, thus enhancing the evaluation of the surface energy of the surface.
Specifically, this technique uses the confocal device to measure some parameters of the drop, such as the height (ℎ) and the apparent diameter (), in a top-view configuration. The drop volume is already known and small enough to discard gravity effects, so the shape of the drop can be approximated by a truncated sphere. Several purely geometric calculations are available to calculate the radius de of the drop and subsequently, the contact angle.
This work reports the first results of the ongoing validation study of this technique and the several mathematical calculations employed to extract the contact angle value. These initial measurements were performed for a hydrophobic surface with water as a measurement liquid. The contact angles for different set of drops for this sample were also measured by a commercial contact angle meter in side-view configuration, with the same liquid and drop dimensions, in order to verify the validity and the accuracy of the presented technique. This validation of the calculation of the contact angle is the first step for the further validation of the developed measurement method for the surface energy determination.