**2. Application**

As an application of PU in biomedical devices, in this paragraph we present our clinical experience with ureteral stents. In particular the focus is driven on the *in vivo* efficacy of PU stents and their surface modification with heparin or with diamond-like carbon. Parameters like biofilm formation, inorganic encrustation extent, stiffness, brittleness or failure of the PU material depending on the indwelling time will be examined. The surface chemistry and morphology characterization of the indwelled stents will also be evaluated according to the surface coating and biofilm formation. The characterization techniques used in this work included Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDS), and Infrared (IR) spectroscopy.
