Energy Dissipation at Ultrasonically Oscillating Superhydrophobic Surface in Various Liquids

A film with a superhydrophobic rough surface was prepared on an AT-cut quartz crystal resonator (QCR). Using the QCR with the film, we measured energy dissipation at the ultrasonically oscillating superhydrophobic surface in various liquids such as water, ethanol and water–glycerol mixtures. The QCR was successfully used to determine the mode of contact of the rough surface with each liquid, i.e., either Wenzel or Cassie contact. Furthermore, it was found that the interfacial friction strongly depended on the contact mode. The interfacial friction was reduced by ca. 50% when the contact mode was the Cassie type.