title: Asymmetric and Speed-Dependent Capillary Force Hysteresis and Relaxation of a Suddenly Stopped Moving Contact Line.
abstract: We report on direct atomic-force-microscope measurements of capillary force hysteresis (CFH) and relaxation of a circular moving contact line (CL) formed on a long micron-sized hydrophobic fiber intersecting a water-air interface. The measured CFH and CL relaxation show a strong asymmetric speed dependence in the advancing and receding directions. A unified model based on force-assisted barrier crossing is utilized to find the underlying energy barrier Eb and size λ associated with the defects on the fiber surface. The experiment demonstrates that the pinning (relaxation) and depinning dynamics of the CL can be described by a common microscopic framework, and the advancing and receding CLs are influenced by two different sets of relatively wetting and nonwetting defects on the fiber surface.
authors.affiliation: Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Dongshi
authors.initials: D
authors.lastname: Guan
authors.affiliation: Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Yong Jian
authors.initials: YJ
authors.lastname: Wang
authors.affiliation: Laboratoire Interdisciplinaire de Physique, Université Joseph Fourier, 140 rue de la physique, F-38402 Grenoble, France.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Charlaix
authors.affiliation: Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Penger
authors.initials: P
authors.lastname: Tong