Impedance-engineered silk/rGO core-sheath fibers for embroidered quasi-frequency selective textiles with broadband microwave absorption

Frequency selective surfaces (FSSs) are critical for modern defense and wearable electronics due to their thin thickness and precise tunability. However, conventional rigid FSSs lack conformality to complex targets, while emerging flexible film-based alternatives often suffer from insufficient mechanical durability and poor wearing comfort. To address these limitations, this study presents a novel strategy for constructing programmable textile-based quasi-FSSs (q-FSSs) by exploiting the spatial configuration of functional single fibers. Initially, core-sheath silk/reduced graphene oxide (S/rGO) fibers with a low linear density of 50 tex (g/km) were fabricated via converging-flow coaxial wet spinning. These fibers exhibit strong orientation-dependent electromagnetic properties, achieving a minimum reflection loss ( RL min ) of -64.03 dB when aligned parallel to the incident electric field. Leveraging the equivalent circuit model, fiber anisotropy was translated into programmable quasi-frequency selective surfaces via embroidery-based patterning, enabling the design of cross-, rhombus-, and square-patterned unit cells. These spatial geometries distinctly modulated current distribution and resonant behavior, allowing independent tuning of equivalent capacitance and inductance. As a result, their resonant absorption peaks are tailored to 11.88, 8.26, and 8.22 GHz, respectively. Notably, the cross-patterned q-FSS achieved high-efficiency microwave absorption with a lightweight areal density (176.3 g/m2), small-thickness (1.89 mm), strong (-64.24 dB), and broadband (4.2 GHz), surpassing similar MAMs. This work provides theoretical insights into the relationship between fiber spatial configuration and microwave absorption performance, offering a promising pathway for the development of next-generation flexible electronic and stealth technologies.