University of Maryland (UMD) researchers have developed a shape-changing 3D printer nozzle designed to address a specific method for 3D printing fiber composites. The nozzle can transform to change the orientation of short fibers in materials like carbon fiber to improve properties like strength or electrical conductivity.
In an article published in Advanced Materials Technologies, the team discusses how actuators change the shape of the nozzle. Ryan Sochol, assistant professor of mechanical engineering and director of the Bioinspired Advanced Manufacturing (BAM) laboratory at UMD’s A. James Clark School of Engineering, said, “When you 3D print with the morphing nozzle, the force is on your side actuators like a can Balloon can be inflated to change the shape of the nozzle and thus the orientation of the fibers. “
The nozzle consists of flexible bubbles that are pneumatically inflated. This changes the shape of the 3D printer nozzle from a straight channel to a converging-diverging geometry, which changes the orientation of the fibers within the print medium.
In particular, the team applies its new technology to 4D printing materials, which can switch from anisotropic to isotropic properties. The UMD professor of mechanical engineering, David Bigio, co-author of the study, explained: “In our work we examined how printed parts swell when immersed in water and whether we can change this swelling behavior with the help of our morphing nozzle.”
When the parts are immersed in water, swelling can occur in one direction (anisotropic) or in all directions (isotropic). These properties can be built into the parts and the printing process. Thanks to the shape-changing nozzle, there is no need to use multiple materials. Connor Armstrong, lead author of the study, said, “It was exciting to discover that we can transition a single print material between anisotropic and isotropic swell by changing the shape of the nozzle during the 3D printing process.”
“Importantly, the nozzle’s ability to transform and equalize the score for swell properties is not limited to 4D printing,” added Noah Todd, co-author of the study and recently graduated engineering student. adds: “Our approach could be used for 3D printing of many other composite materials, for example to adapt their elastic, thermal, magnetic or electrical properties. “
The team tested the nozzle with carbon microfiber hydrogels, changed the nozzle actuation pressure from 0 to 100 kPa, thereby reducing the number of fibers aligned. This caused a shift from anisotropic to isotropic water-induced swelling.
While the nozzle is intended for extrusion 3D printing, Stratasys PolyJet was used to print the nozzle itself. Flexible materials were used for the inflatable side actuators and the central morphing channel, as well as rigid materials for the outer housing and access openings. Abdullah Alsharhan, co-author of the study and a graduate student in mechanical engineering, said, “By using PolyJet multi-material 3D printing, we were able to design the nozzle with an operating power range or range of print sizes that can be reproduced in virtually any research laboratory . “
Applications for which the group is considering using this technology include 3D printing of biomedical objects that change shape based on specific stimuli from the body, as well as the manufacture of weapons for the military.
“By giving researchers an accessible way to 3D print fiber-filled composites, they can control their fiber orientations and thus their ultimate performance when needed,” said Sochol. “This work opens the door to new applications of 3D printing. Take advantage of these unique material properties and the special abilities they make possible. “
The UMD team has developed an interesting addition to the growing number of 3D printing technologies for fiber composite materials. Perhaps the most analogous process to what UMD did is that of Fortify, a startup that uses digital light processing for 3D printing composites. What makes Fortify’s process unique is the ability to use magnets to align the short fibers in its resins. Otherwise, most of the other companies in the 3D printing of fiber composites (Markforged, Desktop Metal, Anisoprint, Continuous Composites, Arevo, 9T Labs, etc.) focus on 3D printing continuous strands of reinforcing fibers. In addition, none of these companies focused on the 4D printing we know.