The 3D printed parts can be conductive by embedding conductive metals or carbon-based nanomaterials in the filament. This is useful for example for making electromagnetic devices, (electrochemical) sensors, circuits, electrochemical cells, and even batteries. The possibility of designing and printing different shapes is also useful for changing the aspect ratio of the 3D printed object, or to print objects with high surface area for analytical separation, membranes, and molecule capture. This approach, for example, has been shown fruitful for desalinization and (waste)water treatment, and for gas capture using MOFs embedded in the 3D printing material. Another field that has greatly exploited 3D printing is catalysis (Figure ). 3D printers, in this case, can be used not only to make (flow)reactors, mixers,[100,101] multimaterial parts,[102] and so on, but also to embed catalysts directly in the 3D printed material.[103-106] Fig. . Examples of different materials and the impact of 3D printing in pharmaceuticals, where the structure of a pill can be changed at will for changing its dissolution time (a). A similar approach can be used for 3D printed catalysts, where the structure can be changed to have more or less surface area and catalysts present (b).