Wenzel State wettability

Many experimental results have been reported (Patankar 2004 Ran et al. 2008 Shirtcliffe et al. 2005) on the transition of the Wenzel state to the Cassie state. For example, Shirtcliffe et al. (2005) observed the transition of water from the Wenzel state to the Cassie state on patterned copper surfaces with different roughness. Similarly, Ran et al. (2008) studied the surface wettability of nano-porous alumina substrates and were able to transform from the Wenzel state to the Cassie state by systematically changing the hole diameter and hole depth. 

The effect of roughness on the wettability of an idealized sinusoidal surface has been studied with a digital computer. The equations of Wenzel and of Cassie and Baxter are discussed in relation to the model. The heights of the energy barriers between metastable states of a drop are seen to be of utmost importance in determining the magnitude of contact angle hysteresis. 

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