https://scholarworks.unist.ac.kr/handle/201301/8 Wed, 08 Apr 2026 00:41:21 GMT 2026-04-08T00:41:21Z https://scholarworks.unist.ac.kr/handle/201301/91288 Title: Meter-scale heterostructure printing for high-toughness fiber electrodes in intelligent digital apparel Author(s): Lee, Gun-Hee; Lee, Yunheum; Seo, Hyeonyeob; Jo, Kyunghyun; Yeo, Jinwook; Kim, Semin; Bae, Jae-Young; Kim, Chul; Majidi, Carmel; Kang, Jiheong; Kang, Seung-Kyun; Ryu, Seunghwa; Park, Seongjun Abstract: Intelligent digital apparel, which integrates electronic functionalities into clothing, represents the future of healthcare and ubiquitous control in wearable devices. Realizing such apparel necessitates developing meter-scale conductive fibers with high toughness, conductivity, stable conductance under deformation, and mechanical durability. In this study, we present a heterostructure printing method capable of producing meter-scale (similar to 50 m) biphasic conductive fibers that meet these criteria. Our approach involves encapsulating deformable liquid metal particles (LMPs) within a functionalized thermoplastic polyurethane matrix. This encapsulation induces in situ assembly of LMPs during fiber formation, creating a heterostructure that seamlessly integrates the matrix's durability with the LMPs' superior electrical performance. Unlike rigid conductive materials, deformable LMPs offer stretchability and toughness with a low gauge factor. Through precise twisting using an engineered annealing machine, multiple fiber strands are transformed into robust, electrically stable meter-scale electrodes. This advancement enhances their practicality in various intelligent digital apparel applications, such as stretchable displays, wearable healthcare systems, and digital controls. Wed, 30 Apr 2025 15:00:00 GMT https://scholarworks.unist.ac.kr/handle/201301/91288 2025-04-30T15:00:00Z https://scholarworks.unist.ac.kr/handle/201301/91287 Title: Phase-change metal ink with pH-controlled chemical sintering for versatile and scalable fabrication of variable stiffness electronics Author(s): Lee, Simok; Lee, Gun-Hee; Kang, Inho; Jeon, Woojin; Kim, Semin; Ahn, Yejin; Kim, Choong Yeon; Kwon, Do A.; Dickey, Michael D.; Park, Steve; Park, Seongjun; Jeong, Jae-Woong Abstract: Variable stiffness electronics represent the forefront of adaptive technology, integrating rigid and soft electronics in a single system through dynamic mechanical modulation. While gallium's high modulus tuning ratio and rapid phase transitions make it ideal for transformative electronic systems (TES), its liquid-state instability, high surface tension, and unintended phase transitions during processing pose substantial challenges. Here, we introduce STiffness-Adjustable temperature-Responsive ink (STAR ink), a chemically sinterable gallium composite electronic ink designed to overcome these obstacles. STAR ink enables high-resolution (similar to 50 micrometers) circuit patterning, large-scale batch fabrication, and three-dimensional structure coating at room temperature. Through pH-controlled chemical sintering, STAR ink-based TES exhibits exceptional mechanical tunability (tuning ratio: 1465) and electrical conductivity (2.27 x 10(6) siemens per meter). Demonstrated applications-from multilayered variable stiffness printed circuit boards (PCBs) matching standard PCBs' complexity to body-temperature responsive neural probe-underscore STAR ink's potential for reconfigurable electronics across consumer electronics and biomedical devices. Wed, 30 Apr 2025 15:00:00 GMT https://scholarworks.unist.ac.kr/handle/201301/91287 2025-04-30T15:00:00Z https://scholarworks.unist.ac.kr/handle/201301/91286 Title: Self-packaged stretchable printed circuits with ligand-bound liquid metal particles in elastomer Author(s): Seo, Hyeonyeob; Lee, Gun-Hee; Park, Jiwoo; Kim, Dong-Yeong; Son, Yeonzu; Kim, Semin; Nam, Kum Seok; Yang, Congqi; Won, Joonhee; Bae, Jae-Young; Kim, Hyunjun; Kang, Seung-Kyun; Park, Steve; Kang, Jiheong; Park, Seongjun Abstract: Packaging in stretchable electronics is crucial to protect components from environmental damage while preserving mechanical flexibility and providing electrical insulation. The conventional packaging process involves multiple steps that increase in complexity as the number of circuit layers multiply. In this study, we introduce a self-packaged stretchable printed circuit board enabled by the in situ phase separation of liquid metal particles (LMPs) within various polymer matrices during solution-based printing processes. The ligand-bound LMPs (LB-LMPs), engineered to inhibit oxide growth, undergo in situ sintering, prompting vertical phase separation. This synthesis strategy not only achieves high initial conductivity of the LMPs but also encapsulates them within the polymer matrix, preventing leakage and providing electrical insulation. Our method enables multi-layer circuit printing, eliminating the need for additional activation and packaging processes. Furthermore, by integrating conductive materials into packaging layers for selective electrical conductivity, vertical interconnect accesses and conductive pads can be formed, enabling large-scale, stretchable, and leakage-free multi-layer electrical circuits and bio-interfaces. Wed, 30 Apr 2025 15:00:00 GMT https://scholarworks.unist.ac.kr/handle/201301/91286 2025-04-30T15:00:00Z