The graft copolymerization of 2-hydroxyethylmethacrylate (HEMA) and methacrylic acid (MAA) onto a biodegradable and biocompatible polymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV), has been investigated. The one-step process was conducted in aqueous media using for the first time a cationic photoinitiator, triarylsulfonium hexafluoroantimonate salts, upon UV irradiation. Under appropriate conditions, the remaining radicals abstract hydrogen from the PHBHV backbone which initiate the UV-mediated grafting of polymers from the PHBHV surface. This process provides the opportunity to adapt the functionality of the film, thus permitting the control of its wettability as a function of the time of irradiation. In the last demonstration, we demonstrated that UV-mediated graft polymerization is an effective method to micropattern coatings onto PHBHV surface to develop microdevices for biological applications.