Equation of Cassie and Baxter

Equation of Cassie and Baxter. Cassie and Baxter [2] extended Wenzel s treatment to composite surfaces. The same assumptions necessary for the derivation of Wenzel s equation are necessary, except that Equation 66 is replaced by 70, and Equation 68 is replaced by 71. These two changes are direct consequences of the difference between the geometry of composite and noncomposite surfaces. 

Equation (7.35) is known as the equation of Cassie and Baxter. It could be shown theoretically that the free energy barrier between metastable states is greatly reduced on composite surfaces. This may explain the large reduction in hysteresis which has been observed experimentally. 

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