Electromagnetic shielding using flexible embroidery metamaterial absorbers: Design, analysis and experiments

Protecting human body from electromagnetic radiation and enhancing the robustness of wearable devices in complex environments become increasingly important. To address this, a flexible embroidery-based metamaterial absorber (MA) which can absorb electromagnetic waves of specific frequency was proposed in this paper. The MA consists of embroidered frequency selective surface (FSS), scuba knitting fabric and metallized fabric. We firstly propose a simplified simulation model to precisely represent the real-world prototype. Then, the parametric effects on the absorption performance were analyzed using equivalent circuit model and full wave simulation. By comparing the power loss density and the power loss rate of each layer, we discover that the resistive loss of the embroidered FSS plays a dominate role in consuming electromagnetic energy. For in-depth investigations, three prototype samples with high-to-low embroidery densities were fabricated and tested. It was found that the peak absorptivity of second sample (with a medium density of 0.70 mm) can reach up to 99% at 2.39 GHz, which verifies the effectiveness of embroidery-based MAs. Moreover, the comparable absorption performance of diverse prototypes shows that a suitable embroidery density is the premise for effective electromagnetic energy absorption, which provides a measurable design guideline for the future research in this area.