Interacting Properties Of Grooved Copper Substratemonolayered Graphene-liquid Droplet And Self-driving Behaviors Of Droplets

In recent years,with the rapid development of the micro-nano system,the application of micro-nano devices has attracted more and more attention.In this paper,the interaction characteristics between graphene and the copper substrate during the process of adsorption and stripping are studied,and the self-driving behaviours of mercury droplets on the composite surface are explored by using molecular dynamics simulation.The results provide theoretical guidance for designing the nanodevices based on graphene.Many applications of two-dimensional materials based on graphene require largearea,high-quality transferring to a target substrate,so it is urgently necessary to understand the characteristics of the interaction between graphene and the substrate during peeling and transfer.The influence mechanism of the geometry of groove on the surface of copper substrate for the adsorption of graphene during the adsorption and stripping process is explored.The results show that for mono-layered graphene with fixed boundary conditions,when the groove width of the substrate is fixed,the adsorption force of graphene on the copper base increases first and then decreases with the decreases of the distance between the two surfaces.The maximum adsorption force increases with the depth of the groove increases,and when the depth of the groove continues to increase until the graphene fails to adsorb into the bottom of the groove,the adsorption force rapidly decreases.In the process of stripping,the critical force of complete exfoliation of graphene shows a tendency of increasing first and then decreasing with the increasing of the groove's depth,and it is related to the interaction areas between graphene and the groove substrate before exfoliation.When the depth of the groove is fixed and changing the width of it,the variation of the adsorption force between the graphene-substrate depends on the steady-state adsorption configuration of the graphene on the groove of the substrate.During both ends of graphene are fixed,the potential energy between mercury and graphene is higher than that between mercury and copper base.The potential energy of the mercury droplet on copper base-graphene composite surface increases first and then decreases with the increasing of the depth of the groove when keeping the width of the groove as a constant.During the boundary condition of graphene is free,while keeping the width of the groove as a constant,the potential energy of mercury droplet increases with the increasing of the depth of groove,until the droplet cannot be absorbed into groove completely,the potential energy decreases.When graphene fails to adsorb into the bottom of the groove,the contact areas between droplet and the channel increase,resulting in the increasing of the potential energy.For both boundary conditions of graphene,when keeping the depth of the groove as a fixed value,with the increasing of the width of the groove,the potential energy of the mercury droplet increases first and then decreases.After that,the gradient grooved surface covered by the monolayered graphene has been designed to study the flow behaviour of mercury droplet.The results show that the mercury droplet can move spontaneously in the composite surface due to the continuous change in the interacting potential energy between the mercury droplet and the composite substrate.The mechanism is that the adsorption from the composite substrate varies continuously in the droplet-moving direction,i.e.,the asymmetric interacting energy in the groove gradient direction drive the liquid mercury droplet moving on the composite substrate.In this work,the liquid mercury droplet accelerates first and then decelerates on the copper-graphene grooved composite substrate in our present simulations.The moving direction of the droplet is determined by the resultant force from both the monolayered graphene and the grooved copper substrate.The copper substrate plays the adsorption role while the graphene plays the repulsive role.The theoretical understanding of the droplet moving behaviors need further investigation in the view of the liquid surface tension and liquid-solid interacting mechanism.