In the framework of a design-based research project, our Physics Education Research group is currently designing a Digital Learning Module (DLM) about the interaction of cosmic radiation with matter, set in the context of space exploration. A DLM is a new digital learning format developed by our group, consisting of a series of pre-recorded explanatory and experiment videos, interactive elements, an interactive simulation experiment, and expert interviews. To establish a set of effective design principles for the design of the new DLM, we have evaluated the first DLM that we created on the topic of Positron Emission Tomography (PET). The evaluation process involved identifying principles fitting the format of the DLM by integrating different theoretical and empirical studies and then evaluating them through student interviews. In the interactive poster session, we will present how the evaluation of the PET DLM has informed the design of the new DLM, as well as its storyline, experiment videos and interactive simulation experiment.