Nowadays, a significant research effort is devoted to understand and mimic biological lubricants which, in contrast to most man-made lubricants, are based on water. It has been extensively shown that nature overcomes the poor lubricity of water with the addition of biological molecules, mostly proteins. Among these proteins, mucins are recognized as instrumental for biological lubrication. However, the molecular details of their lubricating properties are yet poorly understood. While structural studies of mucins at surfaces have given some insight into this aspect, the fact is that very little is known on the structure of confined mucin films, i.e. the really relevant system in the study of mucin lubrication. We propose to study this system by means of neutron reflectivity experiments employing a recently developed surface force type apparatus that allows the investigation of confined thin films.