Biofilms are the prevalent form of bacterial life on earth. Bacteria aggregate and embed themselves in a hydrogel matrix of extracellular polymeric substances (EPS), often spread over surfaces in thin films. The EPS matrix of biofilms is getting more and more attention from scientists for several reasons. On the one hand, it has been identified as the component of biofilms that is responsible for many of the adverse technological impacts of biofouling, for example for the increase of hydraulic resistance in membrane filtration systems. It has also been shown to provide structural integrity to biofilms and shield the embedded bacteria from chemicals, hampering removal in technological as well as medical environments. On the other hand, the same properties are interesting features for application as a biomaterial. Properties like water retention or the resilience against mechanical and chemical interference are defined by the molecular interactions between the different components of the EPS matrix. Therefore, a targeted biofouling cleaning strategy needs to start with understanding those molecular interactions. Owed to the high complexity and the to date still widely undisclosed molecular composition of biofilm EPS, research on these properties requires the use of models. In this work, several experimental and physical models were applied in order to unravel correlations between chemical composition, structure and mechanical properties of biofilm EPS in membrane filtration systems. @en