Aerial wetting contact angle measurement using confocal microscopy

• Published in: Measurement science & technology Vol. 27; no. 12; pp. 125202 - 125211
• Main Authors: Chesna, Jacob W, Wiedmaier, Bob F, Wang, Jinlin, Samara, Ayman, Leach, Richard K, Her, Tsing-Hua, Smith, Stuart T
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.12.2016
• Subjects: confocal microscopy; contact angle; wettability
• ISSN: 0957-0233; 1361-6501
• DOI: 10.1088/0957-0233/27/12/125202

A method is presented in which the wetting contact angle of a sessile drop is acquired aerially using confocal techniques to measure the radius and the height of a droplet deposited on a planar surface. The repeatability of this method is typically less than 0.25°, and often less than 0.1°, for droplet diameters less than 1 mm. To evaluate accuracy of this method, an instrument uncertainty budget is developed, which predicts a combined uncertainty of 0.91° for a 1 mm diameter water droplet with a contact angle of 110°. For droplets having diameters less than 1 mm and contact angles between 15° and 160°, these droplets approach spherical shape and their contact angles can be computed analytically with less than 1% error. For larger droplets, gravitational deformation needs to be considered.