The UWE-4 (University Würzburg Experimental satellite-4) is the most recent project of the University of Würzburg, Germany, within the roadmap towards formation flying CubeSats and will incorporate for the first time in the UWE program a propulsion system. The project started in 2015 and the satellite was launched in December 2018. The technical objective of the UWE-4 mission is the in-orbit demonstration and characterization of an electric propulsion system for 1U CubeSats.
More on UWE-4 here.