A Grating Shearing Interference Method for Measuring the Contact Angle and the Profile of a Meniscus in an Immiscible System

• Published in: Journal of colloid and interface science Vol. 168; no. 1; pp. 162 - 172
• Main Authors: Shen, Chonghui, Ruth, Douglas W.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.11.1994
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1006/jcis.1994.1405

The measurements of contact angle and the profile of a meniscus close to a contact line are very important aspects of the study of the dynamic spreading of a liquid over a solid surface. We present a shearing interference method using a grating as a beam splitter which enables us to make the measurements of the contact angle and the profile of a meniscus simultaneously. The excellent agreement between the theoretical and the measured static menisci shows that the present method is very accurate. In the contact angle range of 10° ∼ 50°, the accuracy of the measurement of the contact angle is within ±0.35° and the accuracy of the measurement of the slope angle is within ±0.2° at 5 μm and ±0.5° at 150 μm from the contact line. The measurable range of the meniscus is 5 ∼ 150 μm from the contact line. The theory of the shearing interference is presented. Iterative schemes used to reconstruct the profiles of menisci are developed and the convergence behaviors of the iterative schemes are tested by numerical experiments.