With the introduction of an additional interfacial tension (or hysteresis tension) to describe the effect of the surficial roughness on the liquid-solid contact angle hysteresis, both contact angle and its hysteresis were derived from mechanical equilibrium and were perfectly consistent with thermodynamics. This unifies the mechanical and thermodynamic performance, or removes the contradiction existing in classical mechanical and thermodynamic understanding. By combining the sessile drop method with CCD camera and the digital imaging techniques, the contact angle hysteresis of distilled water, diethylene glycol, and 1-butyl alcohol on stainless steel surfaces was measured. The results of the experiments agree very well with the predictions of the hysteresis tension model.

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