Pusan National University Researchers Develop 3D Printing Method for Switchable Soft Actuators

Researchers create a printable liquid crystal elastomer that switches molecular alignment to produce opposite motions on demand from a single material

BUSAN, South Korea, Aug. 10, 2026 /PRNewswire/ -- Soft, shape-changing materials are attracting growing interest in applications ranging from robotics to wearable devices, but conventional 3D printing methods are limited to a single actuation mode in each printed component. A new study demonstrates the first 3D-printable smectic liquid crystal elastomer ink that can switch molecular alignment during printing, allowing the same filament to either elongate or contract when heated. The advance could enable more versatile soft robots, adaptive surfaces, and minimally invasive biomedical devices.

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 

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