US-based researchers have developed a method to precisely control the molecular alignment of liquid crystal elastomers (LCEs) during 3D printing.
Ensuring more predictable shape-morphing and mechanical properties, the discovery allows designing soft materials with highly controlled behavior, which could be applied in fields such as soft robotics, prosthetics, and adaptive structures.
Published in Proceedings of the National Academy of Sciences, this study brings together experts from Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), Princeton University, Lawrence Livermore National Laboratory (LLNL), and Brookhaven National Laboratory (BNL).
Led by Harvard SEAS professor Jennifer Lewis, and Emily Davidson, a faculty member at Princeton, the research was supported by the National Science Foundation, the U.S. Army Research Office, and a research initiative at LLNL. Experimental work was carried out at the National Synchrotron Light Source II at BNL.
“When this project began, we simply didn’t have a good understanding of how to precisely control liquid crystal alignment during extrusion-based 3D printing,” said first author Rodrigo Telles, a SEAS graduate student, Academic Cooperation Program scholar and collaborator with LLNL. “Yet it is their degree of alignment that gives rise to varying amounts of actuation and contraction when heated.”
Improving alignment control in 3D printed LCEs
As explained by the team, LCEs are no ordinary materials. They behave much like biological muscles, expanding and contracting in response to heat. This ability makes them ideal candidates for applications that require materials to shift shape on demand.
But there’s a catch. This behavior depends entirely on how well the material’s rigid molecular components, called mesogens, are aligned. And getting that alignment right during 3D printing has traditionally been an unpredictable process, involving a lot of trial and error.
To bring precision to this process, the researchers turned to wide-angle X-ray scattering (WAXS), a technique that allowed them to monitor mesogen alignment inside the nozzle of a 3D printer in real time. By fine-tuning the nozzle shape, printing speed, and extrusion temperature, they established a set of conditions that reliably control molecular orientation.
It turns out that nozzle design plays a bigger role than one might expect. The study compared tapered and hyperbolic nozzles and found that hyperbolic designs created a far more uniform alignment of mesogens, producing more consistent mechanical properties in the final printed structure.
“In the 3D printing community, most of us use a relatively small number of commercially available printheads. This study showed us that it’s important to pay attention to the details of both nozzle geometry and flow – and that we can exploit them to control material properties,” Davidson said.
The researchers identified two types of filaments, one where the outer layer was well-aligned while the core remained disordered, and another with uniform mesogen orientation throughout. Their findings showed that the way material flows through the nozzle directly determines these structures.
To make sense of this relationship, the team introduced a key parameter known as the Weissenberg number. This dimensionless metric consolidates multiple flow-related factors, allowing researchers to predict how printing conditions will impact molecular alignment. In essence, it provides a roadmap for ensuring LCEs print with the exact mechanical properties required, eliminating much of the guesswork.
The implications of this work extend well beyond the lab. With this level of control, researchers can now design LCE-based materials with precision, whether for artificial muscles, self-adjusting textiles, or structures that change shape in response to their surroundings.
By shifting 3D printing of LCEs from an experimental art to an exact science, this study lays the groundwork for more advanced, functional soft materials that can be reliably manufactured at scale.
Research into 3D printing liquid crystal elastomers
While this study refined LCE alignment, other researchers explored ways to enhance its adaptability and mechanics. For instance, researchers at UC San Diego introduced a 3D printing method for LCEs, allowing for functionally graded properties by adjusting printing parameters.
By fine-tuning temperature during extrusion, they gained precise control over stiffness and contraction, making LCEs more adaptable for soft robotics and artificial muscles. Instead of relying on external methods like mechanical stretching or magnetic fields to align mesogens, the team modified the direct ink writing technique, where liquid ink is extruded and cured under UV light.
Experiments revealed a core-shell structure, with the outer shell cooling quickly and stiffening, while the inner core stayed warm and flexible. Printing at varied temperatures led to different shape-morphing behaviors, including a rudimentary robotic gripper with improved adhesion.
Elsewhere, University of Colorado Denver and the Chinese Southern University of Science and Technology researchers developed a 3D printing material that mimics biological tissues’ behavior. Using Digital Light Processing (DLP) 3D printing, they created a honey-like LCE resin that cures under ultraviolet light, forming photopolymer layers that replicate cartilage-like shock-absorbing properties.
Unlike traditional thin-film LCEs, this method allowed for large-scale, high-resolution structures, including a prototype spinal fusion cage. Mechanical tests showed 12 times greater rate-dependence and 27 times higher strain-energy dissipation than commercial resins, making it ideal for protective gear and medical applications.
What 3D printing trends should you watch out for in 2025?
How is the future of 3D printing shaping up?
To stay up to date with the latest 3D printing news, don’t forget to subscribe to the 3D Printing Industry newsletter or follow us on Twitter, or like our page on Facebook.
While you’re here, why not subscribe to our Youtube channel? Featuring discussion, debriefs, video shorts, and webinar replays.
Featured image shows Emily Davidson and Rodrigo Telles, far right, at the X-ray instrument with former and current Brookhaven National Laboratory researchers. From left: Benjamin Yavitt, Lutz Wiegart, Guillaume Freychet and Mikhail Zhernenkov. Photo via Harvard SEAS.
