Background: This study used molecular dynamics simulations to investigate the wetting properties of a droplet on copper surfaces with different nanostructures to determine the influence of the structural parameter and roughness factor on the wetting properties.

Methods: The simulation results show that the structural parameter h/b can determine the wetting transition of droplets on surfaces. In addition, the critical structural parameter values are 1.5, 1.5, 2.08 and 2.24 for the square pillar, cylinder, frustum and cone nanostructures, respectively. Due to the restriction of the wedge surface on water molecules, the effect of the wedge surface is not the same when the theoretical gap and height of the nanostructures are changed on different surfaces.

Results and Discussion: For the square pillar and the cylinder surfaces, when changing the height or the theoretical gap of the nanostructure, the wedge angle is always the same and is 90o, so the effect of the wedge surface is unchanged for water molecules. For the frustum and the cone surfaces, the wedge angle does not change when the theoretical gap of the nanostructure is changed but when the height of the nanostructure is changed, the wedge angle gradually increases but does not exceed 90o resulting in the restriction of the wedge surface on water molecules gradually increasing. Therefore, for the same height and theoretical gap, the contact angle of the frustum and the cone surfaces is larger than that of the square pillar surfaces and cylinder surfaces due to the effect of the wedge surface. It is also observed that the increased roughness factor helps increase the contact angle of the droplet.

Conclusion: We propose that the wetting properties of the nanostructure surface can be controlled by the structural parameter associated with the surface roughness.

背景：这项研究使用分子动力学模拟来研究液滴在具有不同纳米结构的铜表面上的润湿特性，以确定结构参数和粗糙度因子对润湿特性的影响。

方法：仿真结果表明，结构参数h / b可以确定液滴在表面上的润湿转变。另外，对于方形柱，圆柱体，截锥体和圆锥体纳米结构，关键的结构参数值分别为1.5、1.5、2.08和2.24。由于楔形表面对水分子的限制，当在不同表面上改变纳米结构的理论间隙和高度时，楔形表面的作用是不同的。

结果与讨论：对于方柱和圆柱体表面，当更改纳米结构的高度或理论间隙时，楔角始终是相同的，并且为90o，因此对于水分子，楔面的作用没有变化。对于平截头圆锥面和锥面，当改变纳米结构的理论间隙时，楔角不变，但是当改变纳米结构的高度时，楔角逐渐增大，但不超过90o，从而限制了楔形水分子表面逐渐增加。因此，对于相同的高度和理论间隙，由于楔形表面的作用，平截头圆锥体和圆锥表面的接触角大于方柱表面和圆柱表面的接触角。

结论：我们建议可以通过与表面粗糙度相关的结构参数来控制纳米结构表面的润湿性能。