Harald Rupp Ordinarily, if you want to make a 3D-printed liquid-filled object, you have to inject the liquid after the object has been printed. A new process, however, allows such items to be printed all in one step – and the technology could have some valuable applications. The technique was developed by a team at Germany's Martin Luther University Halle-Wittenberg, led by Prof. Wolfgang Binder and researcher Harald Rupp. It utilizes a unique system that incorporates two 3D printing heads – one builds objects up by extruding successive layers of molten polymer, while the other (an inkjet print head) deposits tiny droplets of liquid.