Stacked natural-fiber fabric mats as green super-substrates: integrated characterization and antenna realizations for smart bandages and 5G wearable IoT

Abstract The increased interest in wearable and body-centric communication systems that use sustainable materials has prompted investigation into natural alternatives to traditional FR-4 and polyester-based materials. The article introduces stacked bamboo-pineapple fabric mats as environmentally friendly green dielectric substrates, combining Bamboo’s rigidity with pineapple fibre’s openness. An extensive structural-property connection was established through mechanical testing, morphological analysis (FESEM), elemental composition (EDX), moisture vapour transmission rate (MVTR), and broadband dielectric characterisation at 1–10 GHz. The bamboo mat had a dielectric constant of ε r = 3.92 and an MVTR of 1780 g m −2 , whereas the pineapple mat had an ε r = 3.68 and a much greater MVTR of 15,440 g m −2 . The dielectric constant of the stacked substrate was also shown to be effective, with ε r ≈ 3.8 and a low loss tangent of 0.015, enabling the antenna to be miniaturised while maintaining consistent electromagnetic characteristics. The stacked substrate was used to realize two patch antennas made of microstrip, which resonated at 2.66 GHz (ISM band) and 3.43 GHz (5G mid-band) and gave measured gains of 5.25 dBi and 5.68 dBi, respectively, with the matching between the stacked substrate and patch is in good impedance (S11 < −17 dB). Flexing test: Bending analysis was performed to verify that the antenna could be flexed to 70 degrees without losing stability, demonstrating mechanical robustness for use as a wearable. On-body safety was confirmed through SAR simulations on a human hand phantom, with the highest averaged 1 g SAR values of less than 1 W kg −1 at both operating frequencies, well below international exposure limits. These findings confirm that bamboo-pineapple-based stacked fabric substrates are mechanically stable, breathable, and electromagnetically efficient, enabling next-generation green wearable antennas, smart bandages, and 5G-enabled wearable internet-of-things systems.