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Measuring the Interaction Force Between a Droplet and a Super-hydrophobic Substrate by the Optical Lever Method
Published on: June 14, 2019
Water droplet motion control on superhydrophobic surfaces: exploiting the Wenzel-to-Cassie transition
Guangming Liu1, Lan Fu, Andrei V Rode
1Department of Applied Mathematics, Research School of Physics and Engineering, The Australian National University , Canberra, ACT 0200, Australia.
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.
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