A team of researchers from KAIST and Seoul National University developed a liquid metal-based e-ink that can shift between soft and rigid states depending on temperature, offering new possibilities for flexible electronics and medical devices.

The research team, led by Jeong Jae-woong of KAIST School of Electrical Engineering and Steve Park of the Department of Materials Science and Engineering alongside Park Sung-joon from Seoul National University, announced their breakthrough on Wednesday.

The team focused on gallium, a metal that is solid at room temperature but melts into a soft liquid at around 29.8°C (85.6°F), to overcome the limitations of traditional rigid electronics.

While gallium’s unique phase change makes it ideal for creating flexible circuits, its tendency to form droplets and instability in liquid form previously made it difficult to use in precise circuit manufacturing.

The team developed a method to control gallium’s acidity (pH) to freely adjust its stiffness. By mixing micrometer-scale gallium particles with a neutral solvent and polymers, they created a stable e-ink that evenly disperses the particles.

When the printed circuit is heated, the neutral solvent generates acidic compounds that dissolve the oxide layer on the gallium, allowing the circuit to conduct electricity. This technology allows for high-resolution printing at room temperature, enabling the production of electronic devices that can switch between rigid and soft states like plastic and rubber respectively.

The team demonstrated a wearable healthcare device that remains rigid until worn, then softens to conform to the body. They also developed a brain probe that remains rigid during insertion but softens inside the brain, minimizing tissue inflammation.

“This research solves longstanding issues in liquid metal printing and enables high-resolution circuit fabrication at room temperature,” Jeong said, adding, “It has potential applications in multifunctional electronics, medical technology, and robotics.”

The study was published in the May 30th, 2025, issue of Science Advances.

[ⓒ 매일경제 & mk.co.kr, 무단 전재, 재배포 및 AI학습 이용 금지]