< From left. Professor Il-Kwon Oh and Hyunsoo Kim, a master's student in the Department of Mechanical Engineering >
No wires. No actuators. Shine light on the metal surface, and it rises like a button. KAIST researchers have developed a metal structure that changes shape using light, without any light-absorbing coating. This technology could open new possibilities for tactile interfaces with physical pop-up buttons, shape displays, next-generation wearable devices, and soft robots.
KAIST (President Choongsik Bae) announced on the 20th of July that a research team led by Professor Il-Kwon Oh from the Department of Mechanical Engineering has developed a technology that transforms a flat NiTi shape-memory alloy (SMA) sheet into a "photothermally driven meta-morphing structure" that rises from a flat surface into a three-dimensional form when exposed to light, using only a single UV-laser process.
Next-generation wearable devices and soft robots require technologies that are thin and lightweight while also being capable of changing into desired shapes when needed. Such technologies are attracting attention as a foundation for shape displays, adaptive surfaces, wearable interfaces, and soft robots.
_1.png "Figure 1. Concept and monolithic fabrication strategy of the UV laser-programmed photothermal SMA kirigami platform.")
< Figure 1. Concept and monolithic fabrication strategy of the UV laser-programmed photothermal SMA kirigami platform. >
The research team designed precise cutting and folding patterns in a flat metal sheet so that it would transform into a predetermined three-dimensional shape. The design principle is based on kirigami, the art of creating three-dimensional structures by cutting paper.
Shape-memory alloys are special metals that return to a pre-programmed shape when heated to a specific temperature, even after being deformed. Because they are lightweight and can generate large forces, they are widely used as key materials for soft robots and wearable actuators. However, conventional photothermal shape-memory alloy actuators have faced a limitation: nickel-titanium alloy (NiTi) surfaces do not absorb near-infrared light efficiently. To compensate for this, separate light-absorbing coatings such as graphene oxide, polymer composites, or titanium nitride (TiN) thin films have typically been applied.
These external coatings can peel off during repeated operation and require additional processing. They can also increase heat capacity, which may slow the response, creating limitations in both manufacturability and actuation performance.
To address this problem, the research team used UV laser micromachining. Through this process, they formed kirigami structures on thin shape-memory alloy (SMA) sheets while simultaneously generating a micro-nano porous titanium oxide (TiOₓ) layer on the surface through laser-induced oxidation. As a result, they were able to significantly increase the absorption of near-infrared light without any separate external coating.
The team also implemented a platform that can precisely control the height of three-dimensional deformation and the resulting force output by adjusting structural parameters such as hinge width and slit width. In other words, the core of this research lies in simultaneously programming both how the structure mechanically deforms and how efficiently it absorbs light within a single metal structure.
Furthermore, the team applied a patterning technique that spatially controls the degree of laser-induced oxidation. This made it possible for different regions to deform sequentially at different speeds, even when exposed uniformly to light of the same intensity. The researchers describe this as "spatiotemporal actuation control." This means that the order and timing of deformation are encoded directly into the material itself through light-absorption properties, without any separate electrical control. It can be seen as a form of photonic logic.
The research team further expanded the photothermal SMA metastructure into three-dimensional shape displays and haptic interfaces by integrating it with a multi-channel near-infrared (NIR) LED array. Each SMA kirigami unit moves independently in response to selectively applied light. Based on this, the team successfully displayed the letter sequence K→A→I→S→T and implemented tactile navigation signals that indicate direction.
_1.png "Figure 2. Demonstration of three-dimensional letter patterns (K→A→I→S→T) and directional navigation haptic cues, achieved by selectively illuminating and independently actuating individual units of the shape-memory alloy meta-morphing structure.")
< Figure 2. Demonstration of three-dimensional letter patterns (K→A→I→S→T) and directional navigation haptic cues, achieved by selectively illuminating and independently actuating individual units of the shape-memory alloy meta-morphing structure. >
Professor Il-Kwon Oh said, "The laser programming technology developed in this study is a manufacturing-friendly platform that encodes both mechanical deformation and optical properties into a single metallic structure without any separate coating process," adding, "It can be widely applied to next-generation intelligent morphing interfaces controlled by light, including adaptive surfaces, interactive haptics, and photothermal soft robots."
Hyunsoo Kim, a master's student in the Department of Mechanical Engineering, served as the first author, while Professor Il-Kwon Oh was the corresponding author. The results were published in the international journal Advanced Science, and the work was also selected for the Inside Back Cover of Advanced Science, Vol. 13, No. 31, published on June 4, 2026.
< Figure 3. Image of the photothermal shape-memory alloy meta-morphing structure featured on the Inside Back Cover of Advanced Science >
Paper title: Monolithic UV-Laser Programming of Photothermally Meta-Morphing SMA Structures: Dual-Encoded Kirigami Mechanics and Photonic Absorbance
DOI: https://doi.org/10.1002/advs.74930
