| Flow-induced voltages can be generated from graphene sheets or carbon nanotubes immersed in electrolyte or polar molecular liquids, the phenomenon of flow-induced voltage can be potentially applied in nano-scaled self-powered devices that offers much promise for nanotechnology in nano electro mechanical systems(NEMS) in pursuit of complex function such as realizing bio-molecular sensing and remote controlling, without additional power or increasing of mass and size. Solutions that are applied in the previous studies about flow-induced voltage such as pure water and methanol aqueous solutions etc. have many defects such as volatile, virose, caustic and thermal dependent of, which limit the application of flow-induced voltage in biology and medical treatment. Also, the systems can not been applied to nano size for their larger order. However, room temperature ionic liquids act as a newly green material, show environmentally friendly, healthily safe and high thermosteady so that they can be potentially used as extraordinary electrolyte in extreme conditions and also are harmless to environment and human beings when applied to NEMSs in biomedical areas. Moreover, nano-sized droplet employed in NEMSs presents strong surface effect which enhances the droplet surface and benefits the induced voltage generation. So, flow-induced voltage generated from room temperature ionic liquids can be applied to realizing nano- sized self- powered.In order to explore self-powered devices that can be applied in nanoelectromechanical system, this work researched the phenomenon of flow-induced voltages generated from nano-size ionic liquids droplet moving along graphene sheet by using the effective molecular dynamics simulations for the first time. According to simulations of different imidazole ionic liquids [EMIM][BF4] and [EMIM][PF6] droplets moving along monolayer graphene sheet, the similar variational trend of the cations’ and anions’ drifting velocities were found that they were nonlinearly increasing to saturation with the droplet moving velocity, which is coincident with the related previous researches. And also, in this paper the possible explanation for the saturation was given that the viscosity resistance gradually increases with the velocity of droplet and equals to the applied external force at last. And compared to previous flow-induced voltage researches, the traditional equation for calculating the induced voltage is developed by not only the anions drifting velocities of the droplet, but also the cations drifting velocities and coulombic interactions were taking into consideration, and flow-induced voltages in μV-scale are obtained from the nano-size simulation systems based on the ionic liquids(ILs) for its enhanced ionic drifting velocities. At last, by comparing simulations of systems composed of two types of ILs with different viscosity and temperature,it was found that the higher temperature lead to the lower ionic viscosity, which weaken then the viscosity resistance of the moving droplet. Then the larger drifting velocities result in larger voltages, which indicate that the viscosity acts as a reduction for the flow-induced voltage.The research results of this paper will be of great importance in self-power devices, which enable realization of medical diagnosis, biomolecules sensing and remote controlling in nano electro mechanical systems... |
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