Boundary slip and interfacial friction properties of confined-water flow on graphene under electrowetting

The boundary slip and interfacial friction properties of confined-water flow on two parallel single-layer graphene sheets with a separation of 6 nm under electrowetting conditions were investigated by molecular dynamics simulation and boundary slip theory. For both electrowetted and uncharged graphenes, the flow velocity profiles perpendicular to the flow direction, shear stress, boundary slip velocity, slip length and interfacial friction coefficient were obtained with a graphene-water Couette flow model. Results show that the slip length increases abruptly when the shear rate is above a critical value. The critical shear rate in the electrowetted graphenes is obviously larger than that in uncharged ones. The interfacial friction coefficient between graphene and water decreases with the shear rate and is increased by electrowetting the graphenes. The water viscosity is independent of the shear rate in both eletrowetted and uncharged graphenes.