ABSTRACT
Abstract-Themeasurementofcontactanglesand,thus,determinationofsolidsurfacetension hasbeenconsideredforyearsasa"comedyoferrors",butinrecentyearstheintroductionof moresophisticatedtechniquesandofcomputer-controlleddevices,alongwithageneralbetter understandingofsurfacestructures,hasledtoagreaterprecisionandaccuracyofmeasurements. However,itiscommontoneglectthedifferencebetweentheadvancingcontactangleandtheYoung's angleortounderestimatetheroleandsignificanceofrecedingcontactangles.Inpreviouspapersan experimentalprocedurehasbeendeveloped,calledtheVibrationInducedEquilibriumContactAngle (VIECA),appliedtoaWilhelmyexperiment,whichappearedtobeabletoprovideareallystableand equilibrium-likevalue:thisprocedurewasbasedonprevious,rareliteratureattemptsatprovidingan operationalandsatisfactorydefinitionofequilibriumcontactangle.TheVIECAresultsseemtobe relatedtotheadvancingandrecedingvaluesthroughsimple,butapproximate,relations.Moreover, theVIECAappearstobeindependentoftheroughnessandheterogeneityofthesurfacesanalysed inthemajorityofcases.Inthepresentpaper,theVIECAmethodisextendedtothesessiledrop techniqueandcomparisonismadewiththecommonadvancingor"static"estimatesofcontactangle. Atheoreticalmodellingofthephysicalsituationinducedbytheapplicationofmechanicalvibrations tothemeniscusortothedropisproposed.Themainconsequenceoftheseresultsisthatthecontact anglesoncommonsurfacesforcommonliquidsareoverestimated;amoresubtleconsequenceisthe effectontheevaluationofthesurfacefreeenergyviathemostcommonsemiempiricalmodels.
