Self-Incandescent Heating-Driven Microstructural Consolidation of Biscrolled Cu/CNT Yarns for Reduced Frequency-Dependent AC Resistance

Developing flexible conductors that combine high conductivity, stable MHz-range electrical behavior, and mechanical durability remains a challenge. This is primarily because conventional bulk-type metals suffer from frequency-dependent AC-resistance increases, while standard composites often exhibit poor interfacial integrity. Here, we address these limitations through the synergistic integration of a biscrolling architecture with a rapid and efficient self-incandescent heating (SIH) post-treatment. The biscrolled structure promotes a uniform 3D distribution of copper, while SIH is associated with local Cu reorganization/reflow-like restructuring, grain growth, and interfacial consolidation within the carbon nanotube (CNT) framework. These microstructural changes are consistent with the formation of a more densified conductive network, leading to a 68.8% enhancement in electrical conductivity (up to 3.63 × 10⁴ S/cm) and a metallic temperature coefficient of resistance (TCR = 3.32 × 10⁻³ °C⁻¹) approaching that of bulk copper. Notably, the yarns exhibit weak frequency dependence of resistance within the measured range (up to 10 MHz), indicating a reduced frequency-dependent increase in resistance compared with solid copper wire. By combining exceptional mechanical resilience under extreme deformation with stable high-frequency performance, SIH-treated biscrolled Cu/CNT yarns emerge as a robust material platform for next-generation flexible conductors and interconnects.