Embedding fibers in 3D printed objects can be used to increase the conductivity or extra strength of these objects. Now, engineers have developed a deformable printing nozzle to change the direction of these fibers during the printing process. Generally, short fibers of functional materials such as carbon are simply mixed into the printing medium and then extruded together. Therefore, they usually end up in a random mess with respect to each other. This is possible for some applications, but not feasible for other applications.
In order to find an alternative with more control, the engineers at the University of Maryland used the "PolyJet printing" process to create a prototype printing nozzle with an inflatable actuator on the side of the nozzle. By selectively drawing air in and out, the shape of the nozzle changes, changing the direction of the fiber in the single print medium that it continuously extrudes.
In the test of the device, the structure was printed with a hydrogel containing carbon microfibers. In some areas, the relatively random orientation of the fibers causes the material to swell equally in all directions when it absorbs water. In other areas, the fiber direction is relatively consistent, causing the material to expand in one direction.
This technology can find its place in a field called "4D printing", in which 3D printed objects change their shape in response to external stimuli. It can also be used for more traditional 3D printed objects that have different elastic, thermal, magnetic or electrical properties in different areas.
"By providing researchers with an accessible method to 3D print fiber-filled composite materials and control their fiber orientation as needed, thereby controlling their final performance, this work opens the door to new applications of 3D printing that utilize These unique material properties and the unique functions they achieve," said Ryan Sochol, an associate professor who participated in this research.
A paper on this research led by Connor Armstrong was recently published in the journal Advanced Materials Technology.