Soft materials that change shape in response to heat are attracting growing interest in applications ranging from soft robotics to wearable technologies and biomedical devices. However, conventional extrusion-based 3D printing limits how these materials move because molecules inside each printed filament align in only one direction, restricting every filament to a single actuation mode.
A new study led by Professor Suk-kyun Ahn from Pusan National University, Republic of Korea, with colleagues from Oak Ridge National Laboratory, USA, has overcome this limitation by developing the first 3D-printable smectic liquid crystal elastomer (LCE) ink that can switch molecular alignment during printing. The researchers programmed the same printed filament to either elongate or contract when heated by simply adjusting printing speed or temperature. This paper was made available online on July 10, 2026, and was published in the journal Nature Communications .
Prof. Ahn said: "Our work provides the first demonstration of switching molecular alignment between two orthogonal directions using a single 3D-printable smectic LCE ink, simply by tuning the printing speed and temperature."
Unlike conventional liquid crystal elastomer printing, which fixes molecular alignment along the print direction, the new approach exploits the unique behavior of smectic liquid crystal inks. The researchers showed that changing the printing speed or temperature switches molecular orientation between two perpendicular directions, determining whether the printed material contracts or elongates when heated.
The team combined direct ink writing with rheological measurements, wide-angle X-ray scattering, and molecular dynamics simulations to uncover the mechanism behind the alignment switching. They then printed two- and three-dimensional structures with programmable shape changes, including lattices, curved structures, and switchable surface topographies. The printed materials also maintained stable performance through repeated heating and cooling cycles.
"Potential real-life applications include soft robotic actuators and artificial muscles, reconfigurable surfaces for haptic displays, and adaptive textures that regulate aerodynamic drag", said Prof. Ahn.
The researchers say programming both elongation and contraction within the same printed filament could simplify the design of future soft machines while expanding the capabilities of 4D printing. Potential applications also include wearable devices and minimally invasive medical tools that change shape when needed.
The study was carried out under laboratory conditions using one smectic liquid crystal elastomer formulation, and further work is needed to adapt the approach to additional materials and larger-scale manufacturing.
"Over the next 5–10 years, this work could help 3D-printed objects go beyond just holding a fixed shape. Instead, they could actively change shape and carry out specific functions," added Prof. Ahn
The team believes that the printing strategy provides a versatile platform for next-generation soft actuators and programmable shape-changing materials.
Reference
Title of original paper: Alignment switching in 3D-printed smectic liquid crystal elastomers
Journal: Nature communications
DOI: https://doi.org/10.1038/s41467-026-75368-z
About Pusan National University
Pusan National University, located in Busan, South Korea, was founded in 1946 and is now the No. 1 national university of South Korea in research and educational competency. The multi-campus university also has other smaller campuses in Yangsan, Miryang, and Ami. The university prides itself on the principles of truth, freedom, and service and has approximately 30,000 students, 1,200 professors, and 750 faculty members. The university comprises 14 colleges (schools) and one independent division, with 103 departments in all.
Website: https://www.pusan.ac.kr/eng/Main.do
About the author
Suk-kyun Ahn is a professor in the School of Chemical Engineering and the Department of Polymer Science and Engineering at PNU, Korea. He received his BS in Chemical Engineering from Sogang University, Korea, in 2006 and his PhD in Polymer Science from the University of Connecticut, USA, in 2011. Before joining PNU, he worked as a postdoctoral researcher at the Center for Nanophase Materials Sciences at Oak Ridge National Laboratory and at the Air Force Research Laboratory. His research interests include liquid crystal-based responsive polymers for applications such as actuators, sensors, smart textiles, and adhesives, as well as the development of high-performance polymer binders and polymer electrolytes for lithium-ion batteries.
Lab website address: https://ahn.pusan.ac.kr
ORCID id:0000-0002-6841-4213
