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
School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea.
Medical Research Center, Seoul National University, Seoul 03080, Republic of Korea.
Sci Adv. 2025 May 30;11(22):eadv4921. doi: 10.1126/sciadv.adv4921.
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 (~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 × 10 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.
可变刚度电子器件代表了自适应技术的前沿，通过动态机械调制将刚性和柔性电子器件集成在一个系统中。虽然镓具有高模量调谐率和快速相变，使其成为变革性电子系统（TES）的理想选择，但其液态不稳定性、高表面张力以及加工过程中意外的相变带来了重大挑战。在此，我们引入了刚度可调的温度响应墨水（STAR墨水），这是一种化学可烧结的镓复合电子墨水，旨在克服这些障碍。STAR墨水能够在室温下实现高分辨率（约50微米）的电路图案化、大规模批量制造以及三维结构涂层。通过pH控制的化学烧结，基于STAR墨水的TES展现出卓越的机械可调性（调谐率：1465）和电导率（2.27×10西门子每米）。从与标准印刷电路板复杂度相匹配的多层可变刚度印刷电路板（PCB）到体温响应神经探针等已展示的应用，突显了STAR墨水在消费电子和生物医学设备等可重构电子领域的潜力。
