title: Electrostatic cloaking of surface structure for dynamic wetting.
abstract: Dynamic wetting problems are fundamental to understanding the interaction between liquids and solids. Even in a superficially simple experimental situation, such as a droplet spreading over a dry surface, the result may depend not only on the liquid properties but also strongly on the substrate-surface properties; even for macroscopically smooth surfaces, the microscopic geometrical roughness can be important. In addition, because surfaces may often be naturally charged or electric fields are used to manipulate fluids, electric effects are crucial components that influence wetting phenomena. We investigate the interplay between electric forces and surface structures in dynamic wetting. Although surface microstructures can significantly hinder spreading, we find that electrostatics can "cloak" the microstructures, that is, deactivate the hindering. We identify the physics in terms of reduction in contact-line friction, which makes the dynamic wetting inertial force dominant and insensitive to the substrate properties.
authors.affiliation: Department of Mechanical Engineering, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nita
authors.affiliation: Department of Mechanics, Linné FLOW Centre, KTH Royal Institute of Technology, Stockholm, Sweden.
authors.forename: Minh
authors.initials: M
authors.lastname: Do-Quang
authors.affiliation: Department of Mechanical Engineering, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Jiayu
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Mechanical Engineering, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Yu-Chung
authors.initials: YC
authors.lastname: Chen
authors.affiliation: Department of Mechanical Engineering, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Yuji
authors.identifier: 0000-0002-6844-1449
authors.initials: Y
authors.lastname: Suzuki
authors.affiliation: Department of Mechanics, Linné FLOW Centre, KTH Royal Institute of Technology, Stockholm, Sweden.
authors.forename: Gustav
authors.identifier: 0000-0003-3336-1462
authors.initials: G
authors.lastname: Amberg
authors.affiliation: Department of Mechanical Engineering, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.; Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency, Tokyo, Japan.
authors.forename: Junichiro
authors.initials: J
authors.lastname: Shiomi
keywords: Dynamic wetting; cloaking; electrostatics; surface microstructure