界面润湿性对石墨烯流固摩擦能量输出的影响

The influence of interface wettability on the energy output from flow-solid friction over graphene

为深入了解界面润湿性对流固摩擦能量输出的影响机制,该文利用石墨烯薄膜制作不同界面接触角的俘能结构并进行实验测试。此外,基于分子动力学理论建立Couette模型并进行仿真验证。研究发现,俘能结构输出的电压随着接触角的增大而增加,接触角为69.5°的俘能结构对应输出的电压是0.95 m V,相比接触角为45°时输出的0.57 m V增长67%;输出的电压极性与溶液流动的方向有关;而且电压幅值与溶液流动速度及浓度有关,与流动速度成非线性关系。结合模拟结果提出一种界面润湿性对流固摩擦能量输出效率的影响机制,结果表明:宏观接触角是表征界面对水分子的束缚力的参数,也是影响溶液在界面附近滑移速度的关键因素,溶液离子拖动电子移动速度受滑移速度影响,并将最终决定输出电压大小。

In order to explore the influencing mechanism between wettability of surface and energy output from flow-solid friction, energy harvesting structures with different contact angle were made with graphene film and tested. Besides, a Couette model was established on the basis of molecular dynamic（MD） method and a simulation was carried out. Experimental results illustrate that a larger contact angle would result in a larger output voltage of energy harvesting structure, and an increase from 45° to 69.5° amounts to a 67% increase in output voltage from0.57 m V to 0.95 m V. The polarity of output voltage is closely related to the flow direction of fluid and the voltage amplitude fits to a non-linear relationship with the fluidic velocity. In addition,the concentration also influences the output voltage. An influencing mechanism between wettability of surface and energy output from flow-solid friction is put forward on the basis of the simulation results. Analysis demonstrates that macroscopic contact angle characterizing the binding forces between fluid and solid phases is a critical factor that affects the fluid＇s slippage near the surface. The ions＇ velocities of charging and discharging are determined by the slippage and it exerts great influences on the amplitude of output voltage.