Nanoroughness impact on liquid-liquid displacement

The influence of surface nanoroughness on the static and dynamic behavior of a solid-water-dodecane contact line is investigated. Surface roughness is found to affect the substrate static and dynamic wettability for root-mean-square roughnesses below 7 nm. The kinetics of liquid-liquid displacement is slowed down drastically by the nanoroughness. Nevertheless, contact line motion is found to be governed by a thermally activated process. This process is not based on a pure molecular adsorption-desorption mechanism. Instead, two different nanoscale local displacements mechanisms occurring in the vicinity of the contact line may account for the thermally activated dynamics: we suggest that both molecular adsorption-desorption processes and contact line pinning on nanodefects play significant roles in controlling water displacement by dodecane on surfaces which are rough at the nanoscale.