Sliding/Rolling phobic droplets along a fiber - measurement of interfacial forces
R. Mead-Hunter, T. Bergen, T. Becker, R. O’Leary, G. Kasper, B. Mullins
Langmuir, 2012, 28 (7), 3483-3488
Phobic droplet−fiber systems possess complex geometries, which have made full characterization of such systems difficult. This work has used atomic force microscopy (AFM) to measure droplet−fiber forces for oil droplets on oleophobic fibers over a range of fiber diameters. The work adapted a previous method and a theoretical model developed by the authors for philic droplet−fiber systems. A Bayesian statistical model was also used to account for the influence of surface roughness on the droplet−fiber force. In general, it has been found that the force required to move a liquid droplet along an oleophobic filter fiber will be less than that required to move a droplet along an oleophilic fiber. However, because of the effects of pinning and/or wetting behavior, this difference may be less than would otherwise be expected. Droplets with a greater contact angle (∼110°) were observed to roll along the fiber, whereas droplets with a lesser contact angle (<90°) would slide.