title: Droplet impact on soft viscoelastic surfaces.
abstract: In this work, we experimentally investigate the impact of water droplets onto soft viscoelastic surfaces with a wide range of impact velocities. Several impact phenomena, which depend on the dynamic interaction between the droplets and viscoelastic surfaces, have been identified and analyzed. At low We, complete rebound is observed when the impact velocity is between a lower and an upper threshold, beyond which droplets are deposited on the surface after impact. At intermediate We, entrapment of an air bubble inside the impinging droplets is found on soft surfaces, while a bubble entrapment on the surface is observed on rigid surfaces. At high We, partial rebound is only identified on the most rigid surface at We≳92. Rebounding droplets behave similarly to elastic drops rebounding on superhydrophobic surfaces and the impact process is independent of surface viscoelasticity. Further, surface viscoelasticity does not influence drop spreading after impact-as the surfaces behave like rigid surfaces-but it does affect drop recoiling. Also, the postimpact drop oscillation on soft viscoelastic surfaces is influenced by dynamic wettability of these surfaces. Comparing sessile drop oscillation with a damped harmonic oscillator allows us to conclude that surface viscoelasticity affects the damping coefficient and liquid surface tension sets the spring constant of the system.
authors.affiliation: State Key Laboratory of Traction Power, Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province, School of Mechanics and Engineering, Southwest Jiaotong University, Chengdu 610031, People's Republic of China.
authors.forename: Longquan
authors.initials: L
authors.lastname: Chen
authors.affiliation: Airbus Group Innovations, 81663 Munich, Germany.
authors.forename: Elmar
authors.initials: E
authors.lastname: Bonaccurso
authors.affiliation: School of Science, Wuhan Institute of Technology, Wuhan 430205, People's Republic of China.
authors.forename: Peigang
authors.initials: P
authors.lastname: Deng
authors.affiliation: College of Materials Science and Engineering, State Key Laboratory of Material Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China.
authors.forename: Haibo
authors.initials: H
authors.lastname: Zhang