Surface morphology control of the Cassie-Wenzel transition: An energy landscape perspective

Surface morphology is widely recognized to influence wetting behavior; however, a comprehensive understanding of how specific morphological factors govern the Cassie-Wenzel transition remains incomplete. In this work, building on a bivariate energy-minimization framework, we focus on a key structural design parameter characterizing individual surface defects and systematically investigate its effect-both independently and in conjunction with surface defect density-on three critical aspects of the Cassie-Wenzel transition: wettability, energy barrier, and static friction. Our results demonstrate that this structural design parameter exerts distinct influences on the Cassie-Wenzel transition, depending on the wetting type: in type A, the Wenzel state is energetically favored, while in type B, the Cassie state represents the global energy minimum. These findings reveal that this parameter modulates the stability and reversibility of wetting states, as well as droplet mobility, through nontrivial energy landscapes. Moreover, we uncover a previously unreported non-monotonic dependence of static friction on the morphological factors, which we attribute to a geometric constraint on the contact angle of the transition state. We anticipate that our findings can offer quantitative design guidelines for engineering surfaces with tunable wettability and droplet transport properties.