Abstract
The proliferation of wearable Internet of Things (IoT) devices has raised significant concerns regarding electromagnetic interference (EMI) and human exposure to radiofrequency radiation. Flexible frequency-selective surfaces (FSS) present a promising spatial filtering solution for targeted EMI shielding; however, achieving wideband rejection alongside structural flexibility, polarization independence, and angular stability remains a complex design challenge. This paper presents the design, multi-objective optimization, and experimental characterization of a flexible FSS tailored for wideband electromagnetic shielding in wearable IoT applications. The proposed FSS unit cell incorporates a modified nested double split-ring resonator screen-printed with silver conductive ink on a flexible polydimethylsiloxane (PDMS) substrate. A hybrid optimization scheme combining full-wave finite-integration technique (FIT) electromagnetic simulations with a Multi-Objective Genetic Algorithm (MOGA) was executed to maximize shielding effectiveness and fractional bandwidth while maintaining stability under oblique incidence and mechanical flexing. The fabricated FSS achieves a shielding effectiveness exceeding 20 dB across a broad frequency range from 2.38 GHz to 6.12 GHz, covering essential wireless bands including 2.4/5 GHz Wi-Fi, Bluetooth, and sub-6 GHz 5G communications. Experimental testing under conformal bending conditions down to a curvature radius of 10 mm demonstrates exceptional performance stability with minimal resonance drift (<2.1%). The lightweight, breathable, and mechanically robust FSS provides an practical methodology for integrating high-performance electromagnetic protection into smart textiles and wearable IoT platforms.
