Surface roughness of machined microchannels and its effect on multiphase boundary conditions

The surface roughness is an important boundary condition needed for a detailed understanding and modeling of multiphase flow in microchannels. In this work the surface roughness and contact angles for the conditions present in machined microchannels were measured for various materials. Surface roughness values are reported. Although the machined microchannels have a higher surface roughness than polished surfaces, the resulting contact angles are very similar. A correlation has been developed that allows for the prediction of the contact angle from the liquid surface tension, volume of the liquid drop, and surface roughness.

► Machined metal surfaces are smoother than plastic surfaces.
► Machined surfaces are as good as polished based on the contact angle.
► The contact angle for any material can predicted with the suggested correlation.