title: Trapping of Water Drops by Line-Shaped Defects on Superhydrophobic Surfaces.
abstract: We have investigated the effect of line-shaped topographical defects on the motion of water drops across superhydrophobic wax surfaces using a high-speed video camera. The defects are introduced onto the superhydrophobic wax surfaces by a scratching procedure. It is demonstrated that the motion of a drop interacting with the defect can be approximated by a damped harmonic oscillator. Whether a drop passes or gets trapped by the defect is determined by the incident speed and the properties of the oscillator, specifically by the damping ratio and a nondimensional forcing constant representing the effects of gravity and pinning forces. We also show that it is possible to predict a critical trapping speed as well as an exit speed in systems with negligible viscous dissipation using a simple work-energy consideration.
authors.affiliation: †Fibre and Polymer Technology, KTH Royal Institute of Technology, Teknikringen 56, SE-100 44 Stockholm, Sweden.
authors.forename: Pontus
authors.initials: P
authors.lastname: Olin
authors.affiliation: ‡Solid Mechanics, Department of Management and Engineering, the Institute of Technology, Linköping University, SE-581 83 Linköping, Sweden.
authors.forename: Stefan B
authors.initials: SB
authors.lastname: Lindström
authors.affiliation: †Fibre and Polymer Technology, KTH Royal Institute of Technology, Teknikringen 56, SE-100 44 Stockholm, Sweden.|§Wallenberg Wood Science Centre, KTH Royal Institute of Technology, Teknikringen 56, SE-100 44 Stockholm, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Wågberg