title: Water droplet motion control on superhydrophobic surfaces: exploiting the Wenzel-to-Cassie transition.
abstract: Water droplets on rough hydrophobic surfaces are known to exist in two states; one in which the droplet is impaled on the surface asperities (Wenzel state) and the other, a superhydrophobic state in which air remains trapped beneath the droplet (Cassie state). Here, we demonstrate that water droplets can transit from the Wenzel-to-Cassie state even though the former is energetically favored. We find that two distinct superhydrophobic states are produced. One is a true Cassie state, whereas the other exhibits superhydrophobicity in the absence of a vapor phase being trapped in the surface roughness. Furthermore, we can selectively drive the motion of water droplets on tilted structured hydrophobic surfaces by exploiting Wenzel-to-Cassie transitions. This can be achieved by heating the substrate or by directly heating the droplet using a laser.
authors.affiliation: Department of Applied Mathematics, Research School of Physics and Engineering, The Australian National University , Canberra, ACT 0200, Australia.
authors.forename: Guangming
authors.initials: G
authors.lastname: Liu
authors.forename: Lan
authors.initials: L
authors.lastname: Fu
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Rode
authors.forename: Vincent S J
authors.initials: VS
authors.lastname: Craig