Pukyong National University

Pukyong National University Develops Stretchable and Contractible Gelatin-Based Electronic Skin

- Research teams led by Professors Kim Yong-hyun and Park Myung-ki … propose potential for AI wearable platforms

A gelatin-based hydrogel sensor that is soft like human skin and highly stretchable―with minimal disruption to electrical signals even after repeated stretching and relaxation―has been successfully developed.

A research team led by Professor Kim Yong-hyun (Department of Display and Semiconductor Engineering) and Professor Park Myung-ki (Department of Chemistry) at Pukyong National University (President Bae Sang-hoon) developed this material, which can reliably detect both subtle human movements and larger joint motions.

When attached to the skin, the material collects signals that, once analyzed through artificial intelligence (AI), can accurately distinguish different human motions. This positions it as a promising next-generation wearable electronic skin (e-skin) platform.

The research team created a soft and elastic base structure resembling human skin by combining gelatin―derived from porcine skin collagen―with glycerol and polyethylene glycol.

They then applied a hybrid conductive network composed of silver nanowires (AgNWs) and a conductive polymer (PEDOT:PSS) to achieve high electrical conductivity and durability. To ensure long-term stability in both form and performance, a glutaraldehyde crosslinking process was used to tightly bind the molecular structure.

The most notable feature of the resulting hydrogel sensor is its extremely low electrical hysteresis (signal distortion). Typically, when a sensor is stretched and released, the electrical signal can become misaligned, causing inconsistent measurements. However, this material maintains signal distortion under 3.5% even when stretched up to 200%, enabling it to consistently deliver stable signals for the same movement. It also demonstrated excellent durability, retaining performance after more than 1,000 cycles of repeated deformation.

Notably, this hydrogel sensor was able to precisely detect not only large body movements―such as finger bending, arm and knee joint motion, walking, and jumping―but also fine physiological signals like pulse, respiration, and facial expression changes when attached to human skin.

The research team connected the sensor to a wireless system to transmit data in real time, which was then analyzed using artificial intelligence (AI). As a result, they successfully classified 13 different types of movements with approximately 97.7% accuracy.

The research findings were published in the world-renowned journal in the field of chemical engineering, <Chemical Engineering Journal> (IF= 13.2), under the title:

“Exceptionally low electrical hysteresis, soft, skin-mimicking gelatin-based conductive hydrogels for machine learning-assisted wireless wearable sensors.”

The research team successfully addressed the fundamental issue of signal instability, which had been a major limitation of conventional hydrogels, and anticipates that this material could be developed into an “intelligent electronic skin” for applications in AI-based human-machine interfaces (HMI) and digital healthcare.

Professor Kim Yong-hyun stated, “Gelatin-based hydrogels are soft like skin, but their instability as sensors has been a significant drawback. Through this study, we have managed to combine softness, reliability, and AI applicability in a single material.“ He added, “We expect this material to be used in diverse fields such as precise biosignal monitoring, rehabilitation and smart fitness coaching, next-generation wearable devices, and robotic e-skin systems.” <Pukyong Today>