Researchers 3D Print Actuators That Expand and Contract on Demand

Pusan National University and ORNL 3D Print Shape-Shifting Actuators

A team from Pusan National University and Oak Ridge National Laboratory has published research in Nature describing 3D-printed elastomeric actuators that expand, contract, and change shape in response to temperature and mechanical input, with no electronics required. The work uses a custom liquid crystal elastomer filament deposited through direct ink writing.

The key material is a smectic liquid crystal elastomeric ink. Liquid crystal polymers sit in an odd category between solid and liquid. Their molecules arrange themselves in ordered structures when melted, and those arrangements shift depending on temperature and mechanical stress. In the smectic phase, molecules stack in neat layers. In the nematic phase, they align directionally without that layered order. By switching between these phases, the printed parts can physically change shape.

What makes the Pusan team's approach different is control. The researchers varied print speed and nozzle temperature during deposition to lock different molecular orientations into different regions of the same part. One section can be programmed to expand when heated, while an adjacent section contracts. The result is a monolithic printed actuator with directional control and no wiring.

The team included researchers from Pusan's School of Chemical Engineering and School of Mechanical Engineering, joined by scientists from ORNL's Neutron Scattering Division and Center for Nanophase Materials Sciences. The neutron scattering work at ORNL helped characterize the molecular alignment inside the printed structures, confirming that the process variables produced the intended smectic and nematic regions.

Potential applications span several fields. Soft robotics is an obvious fit. Microfluidics could use these materials to pump or redirect fluids without external pumps. Optoelectronic components that change light transmission as they deform open design possibilities. The researchers also note the inherent flame resistance and high continuous service temperature of liquid crystal polymers, around 240 degrees Celsius, which gives these actuators a performance envelope most soft materials cannot match.

This is early-stage academic research, not a shipping product. The Pusan team explicitly positioned their work as an enabler for other researchers rather than a finished commercial system. The real significance is the proof that molecular orientation can be programmed directly into a 3D printing process. That is a capability most desktop or industrial printers do not currently offer, and it points toward a future class of programmable, shape-shifting printed parts.