Misconceptions in the Youngs Equation

Most researchers would agree that surface science started with Thomas Young when he published his legendary article in 1805 entitled An Essay on the Cohesion of Fluids [1]. Young did not write any equation in his paper, but he descriptively stated that an angle is formed when liquid wets a solid surface. He wrote We may 

Young clearly stated that the angle of contact is a result of the mechanical equilibrium among the three surface tensions ( lv. sl. and ysv) at the three-phase contact line. However, it is somewhat a mystery that there are still misquotations in recent years, either by implying or directly stating, that the contact angle is from a thermodynamically equilibrium wetting state. Such a quotation is not correct. 

This methodology has been extended to define oleophilicity/oleophobicity for hexadecane. A surface can be defined as oleophilic when its hexadecane Or is 124° and oleophobic when the hexadecane Or is 124°. The finding clearly demonstrates the incorrect presumption that the 90° cutoff is universal for all liquids. Essentially, the philicity/phobicity cutoff is dependent of the surface tension of the liquid, the lower the surface tension, the larger the Or cutoff. 

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