Effiects of surface roughness on oil-water-solid three-phase contact line

We established a dodecane-water-graphite system from molecular dynamics insight. The effiects of surface roughness on the three-phase contact line are studied from the aspects of the microscopic contact angle, adsorption property of water and oil molecules and adsorption energy of water molecules. The results show that adsorption intensity is weaker with the existence of roughness, which causes a larger contact angle when surface in water side has raised structure and a smaller contact angle when surface in oil side has raised structure. Oil molecules near solid surface exhibit a layer-by-layer distribution and roughness has little effiect on it. The existence of roughness weakens the orientation of water molecules, which results in weaker adsorption and stability.