Hagen works at the moment in the DFG research group NANOMEE on multiscale simulations of biomineralization. In the EU young research group InnoMecTec he focused on modeling photocatalytic systems to remove pharmaceuticals from wastewater. Multiple research stays in Japan, Portugal and the USA helped him to develop a wide variety of computational technics. Hagen also incorporated these experiences were in his role as the data analyst for the two German university ranking projects sponsored by the Federal Foreign Office of Germany. During his study of material science at the Dresden University of Technology he worked on multiscale simulations of charge transport in silicon nanowire-based transistors and modeling of cluster formation in nuclear reactor containment steel.