Dielectric characterization of pineapple leaf fibre (PALF) reinforced Polydimethylsiloxane (PDMS) composites as a potential antenna substrate for wearable antenna application

The rapid growth of wearable technology has created a demand for antenna substrates that are flexible, lightweight, and high-performance, while maintaining safety for human use, particularly under bending and on-body conditions. Natural fibre–polymer composites have emerged as a sustainable alternative, but their dielectric performance, mechanical robustness under bending, and impact on specific absorption rate (SAR) remain underexplored, leaving a critical gap in wearable antenna research. To address this, Pineapple Leaf Fibre (PALF) reinforced Polydimethylsiloxane (PDMS) composites were fabricated using Hand Lay-Up and Manual Polymer Mixing methods, with fibre loadings ranging from 10 wt.% to 90 wt.% and fibres subjected to alkaline treatment with 1.5M Sodium Hydroxide (NaOH) to enhance fibre–matrix adhesion. Dielectric characterization using a Vector Network Analyzer revealed that pure composites achieved dielectric constants from 1.65 to 2.63, while treated composites improved to 1.58–2.98, with the loss tangent reduced from 0.44 to 0.41 at 2.45 GHz; the Hand Lay-Up method was discontinued due to very low dielectric constant (< 2.0). Antenna prototypes simulated in CST Studio demonstrated enhanced return loss (up to −28dB), radiation efficiency (> 52 %), and stable radiation patterns under bending, with SAR analysis confirming safe levels for wearable use. These findings demonstrate that PALF-PDMS substrates not only provide superior electromagnetic performance and mechanical flexibility but also offer environmental sustainability, positioning them as a promising material for advanced wearable antenna applications.