title: Actuating Water Droplets on Graphene via Surface Wettability Gradients.
abstract: A surface wettability gradient can break the equilibrium status of a liquid droplet and drives its unidirectional movement on the surface. We propose a conceptual design of the driving water droplet on a graphene surface and demonstrate that both speed and direction of the movement can be controlled via a continuous gradient of surface wettability using comprehensive molecular dynamics (MD) simulations. Controlling the water droplet toward linear and nonlinear arc paths is exemplified in one- and two-dimensional gradients of surface wettability, respectively. Unbalanced Young's equation is extended to understand the speed of the droplet movement, and the predications agree well with MD simulations.
authors.affiliation: Department of Mechanical and Aerospace Engineering, and ‡Institute for Nanoscale and Quantum Scientific and Technological Advanced Research, University of Virginia , Charlottesville, Virginia 22904, United States.
authors.forename: Qingchang
authors.initials: Q
authors.lastname: Liu
authors.affiliation: Department of Mechanical and Aerospace Engineering, and ‡Institute for Nanoscale and Quantum Scientific and Technological Advanced Research, University of Virginia , Charlottesville, Virginia 22904, United States.
authors.forename: Baoxing
authors.initials: B
authors.lastname: Xu
mesh_terms: D006108:Graphite / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D014867:Water / Q000737:chemistry*; D017155:Wettability
chemical_list: D014867:Water; D006108:Graphite