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When Sessile Drops Are No Longer Small: Transitions from Spherical to Fully Flattened
We measured the dimensions and contact angles of sessile drops using three liquids on a variety of polymer and silicon surfaces. Drops ranged in size from a few microliters to several milliliters. With increasing liquid volume, heights of the drops initially rose steeply and then gradually tapered t...
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Published in: | Langmuir 2010-07, Vol.26 (14), p.11815-11822 |
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Main Authors: | , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | We measured the dimensions and contact angles of sessile drops using three liquids on a variety of polymer and silicon surfaces. Drops ranged in size from a few microliters to several milliliters. With increasing liquid volume, heights of the drops initially rose steeply and then gradually tapered to a constant value. The heights of small, undistorted drops as well as the heights of the largest drops were accurately predicted by well-established models. A recently derived expression for meniscus height was used to estimate the heights of intermediate-size drops. While it was not exact, this expression produced reasonable approximations without having to resort to iterative numerical methods. We also identified transition points where gravity began to distort drop shape and ultimately limited drop height. Relatively simple closed analytical expressions for estimating these transition points were also derived. Predicted values of the height and volume at the onset of distortion agreed fairly well with the measured ones. Contact angles carefully measured by the tangent method were independent of drop size. |
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ISSN: | 0743-7463 1520-5827 |
DOI: | 10.1021/la1005133 |