KAIST

< (From left) KAIST Ph.D. students Sangyoon Bae and Professor Seong Su Kim, Ph.D. student Dajeong Kang, and Dr. Wonvin Kim >

While space structures and robotic arms require lightweight actuation devices capable of repetitive movement, conventional motor-based systems face limitations due to their heavy weight and complex structures. A KAIST research team has developed a smart material-based actuation technology that operates rapidly in less than a second without a motor, suggesting new possibilities for next-generation robotics and space deployable structures. 

KAIST announced on the 22nd that a research team led by Professor Seong Su Kim from the Department of Mechanical Engineering has developed a "two-way shape memory material-based hybrid smart actuator" capable of "reversible self-shape change." This technology allows the material to change its shape in response to external stimuli, such as heat, and return to its original state without the need for additional complex mechanical devices.

The research team designed a hybrid composite actuator that combines Shape Memory Alloys (SMA) and Shape Memory Polymers (SMP) to leverage the advantages of both materials. SMAs are metallic materials that return to their original shape when heated, while SMPs are polymer materials that change shape in response to heat or other external stimuli.

Conventional shape memory materials had limitations; they either could not return to their original state once deformed (one-way) or had extremely slow recovery speeds. Furthermore, because metal alloys and polymer materials have different levels of stiffness, they often failed to restore their shape accurately during repetitive use.

To solve these issues, the research team improved both the material and its structure. First, they adjusted the chemical composition of the SMP and reinforced it with carbon fibers to make the material more rigid. Additionally, they applied a "tape spring" structure—similar to a retractable measuring tape—to the actuator. This structure creates a "snap-through" phenomenon, where energy is stored during deformation and released instantaneously, significantly increasing both the speed and accuracy of the movement.

As a result, the developed actuator achieved full two-way actuation, bending when heated and flattening again as the temperature drops. The technology also demonstrated a significantly increased range of deformation and a nearly 100% recovery rate to the initial shape. The recovery speed was also greatly improved, confirming that the actuator can operate repeatedly without the need for complex control systems.

< Development process of the SMA-SMP hybrid two-way actuator >

The shape memory actuator developed in this study is highly significant as it simultaneously achieves two-way deformation, sub-second actuation speed, and high deployment accuracy. This achievement is evaluated as a major step forward in the practical application of shape memory material-based actuation technology.

Professor Seong Su Kim stated, "This research overcomes the physical limitations of materials through original structural design, elevating the performance of shape memory actuators to the next level. We expect this technology to be applied in various fields, such as robotic grippers requiring repetitive motions or deployable structures for space applications."

Dajeong Kang, a Ph.D. student, participated as the lead author of this study. The paper was published online on January 19, 2026, in Advanced Functional Materials, an international journal published by Wiley. In recognition of its excellence, the study was featured as the Front Cover of the March 2026 issue of Advanced Functional Materials.

Paper Title: Two-Way Shape Memory Alloy and Polymer Composite Hybrid Smart Actuator With High Speed, Accuracy, and Reversible Deformation DOI: https://doi.org/10.1002/adfm.202528863 Author Information: Dajeong Kang (KAIST, First Author), Seong Yeon Park (KAIST, Co-author), Yitro Samuel Aditya (KAIST, Co-author), Ha Eun Lee (KAIST, Co-author), Wonvin Kim (KAIST, Co-author), Sangyoon Bae (KAIST, Co-author), and Seong Su Kim (KAIST, Corresponding Author)

< Image of the Front Cover of Advanced Functional Materials >

This research was conducted with the support of the Nano and Materials Technology Development Program (Project No. RS-2024-00450477) and the National Semiconductor Research Laboratory Core Technology Development Program (Project No. RS-2023-00260461) funded by the Ministry of Science and ICT and the National Research Foundation of Korea.