Aims:The wetting properties of the nanostructure surface can be controlled by the structural parameter associate with roughness surface.
Increasing the roughness of hydrophobic surface can enhance the hydrophobicity of the surface.
We chose copper material modified by fluorosilane as the substrate, and used Lammps software to establish four different shapes nanostructures, square pillar, cylinder, frustum and cone nanostructure respectively with pillar height and theoretical gap changing to study the influence of structural parameter and roughness factor on wetting properties of surfaces.
Molercular dynamic simulation.
The structural parameter h/b can determine the wetting transition of the droplet on surfaces. With 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 wedge surface.
(1)The values of the contact angle exhibit a strong dependence on roughness factor. The roughness factor will increase by this way of increasing height and decreasing gap, and the contact angle of droplet increase with the roughness factor increasing on the four surfaces. There exists the critical structural parameter h/b to determine the Cassie and Wenzel state transition of the droplet on various nanostructure surfaces.And 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.
The wetting properties can be controlled by the structural parameter associate with the roughness factor. Increasing the pillar height and decreasing the gap of the nanostructure surfaces will make the structural parameters reach the standard of transition value h/b of the droplet state, and the droplet will change from Wenzel state to Cassie state.