Wetting behaviors of water droplet on rough metal substrates

In this paper, an experimental investigation of wetting behaviors of water droplet on rough metal substrates is presented, in order to study the influence of rough structures on contact angles of metal substrates. The static contact angles and contact angles evolution over time are measured with a video contact angle analyzer. The results show that the hydrophobic property increases with increase of surface roughness. The contact angle increases from 76.8 degrees to 86.7 degrees with increasing mean roughness from 1.435 mu m to 5.591 mu m. The surface with large aspect ratio displays larger contact angle than surface with low aspect ratio. The apparent decrease of the variation of contact angle as a linear variation with the time changing, the droplet spreads on flat substrates with low roughness slowly. Compare with Cassie state, Wenzel wetting state is more sensitive to the change of surface roughness. It may be expected to use the reasonable lapping process and parameters to control the static contact angle of water droplets on the metal surfaces.