The rise and demise of the Young surface tension diagram; a final celebration and respectful farewell

Robert Finn

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Submission date: 09. Dec. 2009
Bibtex
MSC-Numbers: 76B45
Keywords and phrases: capillarity, surface tension, contact angle

Abstract:
The Young diagram for determining the contact angle at a triple interface formed by two fluids with a solid, although based on speculative reasoning, found initially a universal acceptance, without reservation. Later expository articles pointed out consequences that had initially been overlooked, but which were consistent in the specific cases considered. Some authors then produced reasoning disputing the construction, and examples - most recently by the present author - were introduced, putting the underlying concept into serious doubt. Nevertheless, the construction remains firmly embedded in the curricula of major universities and institutes throughout the world; it continues to be used in engineering design, and some articles emphatically defending it have appeared recently in major journals. The present work outlines past literature and provides a more precise statement of the Young assertion than is customary. It comments on the reasoning in one of the articles defending the assertion, and also presents a further example, indicating conceptual difficulties to which one is led by the premises of that reference.