Assessing the Accuracy of Contact Angle Measurements for Sessile Drops on Liquid-Repellent Surfaces
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McKinley_Assessing the accuracy.pdf
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Author(s)
Srinivasan, Siddarth
McKinley, Gareth H.
Cohen, Robert E.
Date Issued
November 2011
Journal
Langmuir
Publisher
American Chemical Society (ACS)
Citation
Srinivasan, Siddarth, Gareth H. McKinley, and Robert E. Cohen. “Assessing the Accuracy of Contact Angle Measurements for Sessile Drops on Liquid-Repellent Surfaces.” Langmuir 27.22 (2011): 13582–13589.
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Author's final manuscript
Abstract
Gravity-induced sagging can amplify variations in goniometric measurements of the contact angles of sessile drops on super-liquid-repellent surfaces. The very large value of the effective contact angle leads to increased optical noise in the drop profile near the solid–liquid free surface and the progressive failure of simple geometric approximations. We demonstrate a systematic approach to determining the effective contact angle of drops on super-repellent surfaces. We use a perturbation solution of the Bashforth–Adams equation to estimate the contact angles of sessile drops of water, ethylene glycol, and diiodomethane on an omniphobic surface using direct measurements of the maximum drop width and height. The results and analysis can be represented in terms of a dimensionless Bond number that depends on the maximum drop width and the capillary length of the liquid to quantify the extent of gravity-induced sagging. Finally, we illustrate the inherent sensitivity of goniometric contact angle measurement techniques to drop dimensions as the apparent contact angle approaches 180°.
MIT Department
Massachusetts Institute of Technology. Department of Chemical Engineering
Massachusetts Institute of Technology. Department of Mechanical Engineering
Massachusetts Institute of Technology. School of Engineering
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1021/la2031208
