KAIST develops shape-memory alloy structure that rises at the touch of light

KAIST mechanical engineering professor Oh Il-kwon (left) and master's student Kim Hyun-su. [KAIST]

"Shine light on it, and a button rises on its own."

South Korean researchers have developed a new metal structure that changes shape using light alone — no wiring or separate coating required.

KAIST announced Monday that a research team led by Oh Il-kwon, a professor in the Department of Mechanical Engineering, has developed a technology to transform a flat nickel-titanium shape-memory alloy (SMA) sheet into a metamorphing structure — one that deforms into a pre-designed three-dimensional form when exposed to light — using a single UV laser process.

The ability to change shape freely on demand, while remaining thin and lightweight, is central to next-generation wearable devices and soft robots. Researchers say the technology could underpin a range of future applications, including shape displays, adaptive surfaces, wearable interfaces and soft robotics.

The shape-memory alloy metamorphing structure independently drives each unit through selective light input to render letter patterns (K→A→I→S→T) and directional navigation haptic signals in three dimensions. [KAIST]

The research team designed precise cut-and-fold patterns into a flat metal sheet so that it deforms into a predetermined three-dimensional shape. The approach applies the principles of kirigami — the art of creating three-dimensional structures by cutting paper — to metal.

Shape-memory alloys are lightweight yet capable of generating substantial force, making them a key actuating material for wearable devices and soft robots. Existing technologies, however, required a separate light-absorbing coating because the metal does not absorb light efficiently on its own. Coatings such as graphene oxide and titanium nitride can peel off with repeated use, complicate the fabrication process and reduce response speed.

To overcome these limitations, the team turned to UV laser micromachining. A single laser pass both cuts the metal into the desired shape and roughens the surface to absorb light effectively, eliminating the need for any additional coating.

The back cover of the June 4 issue of the international journal Advanced Science, which published the research findings. [KAIST]

A key innovation of the research is that the team encoded not only how much the metal deforms, but also the sequence in which it does so — all within a single piece of metal. By adjusting the laser machining parameters, the researchers made certain sections transform before others when exposed to the same light, allowing the metal to follow a programmed sequence without any electrical signals or complex control systems.

The team combined the technology with near-infrared LEDs to demonstrate a shape display and haptic interface in which parts of a surface physically rise. They also succeeded in sequentially displaying the letters K, A, I, S and T, and in generating tactile signals that guide a user's fingertip in a given direction.

The research team said that as the technology matures, it could be used in smartwatches, augmented and virtual reality gloves, robot teleoperation interfaces, and braille or directional guidance displays — all as next-generation tactile displays that convey information through surfaces that physically rise.

"The most distinctive aspect of this research is that a single UV laser process simultaneously designs both the mechanical structure and the optical surface properties," Oh said. "The technology can be extended to fields such as actively deforming robot skin, wearable haptic interfaces, soft robots and microrobots."

The findings were published in the international journal Advanced Science.

nbgkoo@heraldcorp.com